Snow loads on roofs 1963-64: eighth progress report

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Snow loads on roofs 1963-64: eighth progress report

NATIONAL RESEARCH COUNCIL CANADA

DIVISION OF BUILDING RESEARCH

SNOW LOADS ON ROOFS 1963-64 EIGHTH PROGRESS REPORT

by

G. Pernica and B. G. W. Peter

Internal Report No. 324 of the

Division of Building Research

OTTAWA

Novem.ber 1966

PREFACE

The prediction of roof snow loads involves consideration of many factors, in addition to basic ground snow loads. Wind, local shelter, roof shape and heat los s all modify the load fr o rn the unif'o r rnl v distributed ground snow load that would ac curnul at e in a horizontal sheltered area such as a clearing in a fore st. The rriod ify ing influences generally reduce the load on exposed, un-obstructed roofs but increase the load in areas where "a.e r odyna mi c s he lt e r " produces deposition of drifting snow.

It is the purpose of this report, the eighth of a serie s of reports on a continuing survey of actual snow loads on roofs, to provide i.nfo r rnat ion for further r e fi.ne rne nt s of the design roof snow loads in the National Building Code of Canada. It presents results of the 1963-64 survey in the fo r rn of graphs, tables, and photographs and includes an appendix on the ground snow load variations at 9 different sites in the Ottawa area observed during the past winter.

The Division of Building Research wishes to express again its appreciation to all those observers whose active participation made possible the survey of the 1963-64 winter. In particular, grateful appreciation is recorded to A Station observers of the Meteorological Branch of the Department of Transport at Goose Bay and Gander; the National Parks Branch of the Department of Northern Affairs and National Resources at P.E.I. National Park; Ecole Polytechnique {Montreal}; Macdonald College (St e , Anne de Bellevue}; Oue ents University {Kingston}; University of Toronto;

University of Manitoba (Winnipeg); University of Alberta (EdInonton); University of Waterloo; Al urrrinurn Corripa.ny of Canada at Arvida; Mrs. p. Curtis at Inuvik; BeaucheInin-Beaton-Lapointe, Consulting Engineers at Wabush (Labrador); and the Atlantic, Prairie and B. C. Regional Stations of the Division. Sincere thanks are also expressed to the Chief of the Air Staff, Air Force Headquarters, Ottawa, and to the RCAF personnel at the C Stations at COInOX,

Lancaster, Cold Lake, Winnipeg, North Bay, Ottawa and Goose Bay, and to the building inspectors and individuals who made B Station observations. Without all this willing co-operation this survey could not have been carried out.

This report was prepared by G. Pernica of the University of Toronto, a su rnrrie r worker with the Building Structures Section, and B.G. W. Peter, research officer with the Section, under the direction of W. R. Schriever.

Ottawa

November 1966

Robe rt F. Legget Director

TABLE OF CONTENTS

SURVEY PROCEDURES OF 1963-64 OBSER VA TIONS A Stations 1 1 B Stations C Stations • • • • • • • • • • • • • • • • • • • • • • • • • " • • 0 0 8 8 "• • • • • • • • • • • • •

...

" " "

.

2 2

RESULTS OF THE 1963-64 OBSERVATIONS

• • • • • • • • 0 • • • • • • • • • • • • • • • • • • •0 " ' • • • • • • • • • • • • • • • • • • • • • • • •'" • • • • • • • • • • • • • • • • • • • G • • III • • • • • • • • • • • • • • • • III • • • •III • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 2 3 3 5 8

9

9

9

• G• • • • • III • • • • • • • • • • • • •

...

" "

.

• • • • • • • • • • • • • • • • • • III • • • 18 • • • • • • • • • • • • • • • • • • • .. • • • • • • • • • • • • • • '" • 18• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •'" • • III • • • • • • • • • • • • • A Stations B Stations C Stations

Ground Snow Load ••• PRESENTATION OF RESULTS

GENERAL DISCUSSION • WEATHER •••••

Ground Snow Density .•. 18• • • • • • • • • • • • • • • 18• • • • • • • • • • • • • • • • • 10

Measurementsof S h e l t e r . . . 10

0 • • • • "' • • • • • • • • • • • • • • • • e . 8 • • • • • • • • • • • • •

'" " "

.

Statistical Distribution of Average Roof Loads INTERIM CONCLUSIONS

REFERENCES •••••••••

...

11

14 15

APPENDIX A: Ground Snow Load Measurements at Nine Site s in the Ottawa Area by B. G. W. Peter

SNOW LOADS ON ROOFS 1963-64 EIGHTH PROGRESS REPORT

by

G. Pernica and B.G. W. Peter

The survey of snow loads on roofs which the Division of Building Re search has conducted during the past seven winter s (l - 7) was continued during 1963-64 generally on the same roofs and with the same objective, i , e. to provide information as a basis for refinements to the design snow loads for roofs in the National Building Code (8). For a detailed description of the background and scope of the survey, readers should refer to earlier reports. This report is, in the main, a summary of the re su It s of all observations taken during the 1963-64 winter. Also included are a graphical resume of some results from the past seven winters and an appendix on the variation of the ground snow depths at a given station.

SURVEY PROCEDURE OF 1963-64 OBSERVATIONS

The survey procedures used this year at A, Band C Stations were sirnilar to those used during the previous year with the exception that the local survey of roofs in Ottawa was discontinued.

A Stations

At the A Stations detailed observations of snow depth and density on the ground and on the roofs are usually recorded once a week and after every heavy snowfall.

At most A Stations at least one flat roof and one gable roof were observed. A total of 45 roofs was observed at the 17 A Stations (Table I). Two new A Stations, Wabush Lake in

Labrador arid Quebec City, both located in heavy snow load areas, were added to the survey. The observations at Wabush Lake were begun in late February of the 1962-63 winter. As they were not received, however, until after the 1962-63 or seventh progress report was completed, this progress report contains the 1962-63 and 1963-64 observations.

2

-The A Station at Glacier, B. C. was discontinued because the uninsulated building was heated, and this caused too much snow rne lt irig ,

B Stations

Observations at the B Stations are taken only after a very heavy snowfall or after an accumulation of snow that has caused unusually high loads for the area or after a structural failure has occurred due to snow load. B Station observers are volunteers who decide for themselves when observations are warranted. Relatively few reports are received each winter. During the 1963-64 winter,

several reports were received from the University of Western Ontario giving observations in the London area while other reports received came from Quebec and the Northwest Territories.

C Stations

At the C Stations, which are all RCAF bases, observers make the equivalent of A Station observations on large roofs located at RCAF bases across Canada. At each station two or more of four standard C Station roofs were observed, the four being the unit supply depot (flat), the cantilever hangar roof (flat), the mechanical equipment garage roof {flat, split level} and the arch hangar roof (curved). On two of the roofs, cantilever hangar and unit supply depot, canopies were also observed in a similar manner to the roof. Twenty-four roofs were observed at the eight C Stations.

WEATHER - Summary

During the 1963-64 winter, the snowfall"across Canada showed considerable variation from the normal especially on the east coast

(P.E.I.,

N.S., NFLD.) where the snowfall was from

41

to 86 per cent above normal. Snowfall was generally far below normal in Ontario and Quebec and near normal in the Prairie and West Coast regions. In general, the mean temperature s from November to April were below normal for Ontario, Quebec and the far north, near normal for the Maritimes and B. C. and above normal on the Prairies. The mild winter experienced on the Prairies was mainly due to an exceptionally mild February which had a mean monthly temperature that was from 80

above normal in Manitoba to 200

3

-PRESENTATION OF RESULTS

A Station observations are presented, as in previous years, separately for each roof by rrie an s of a graph on which the ground load, the ITIaxiITIuITI, average and ITIiniITIuITI roof load, and in SOITIe cases the ITIaxiITIuITI canopy load are plotted against ti rne ,

Also shown on the graphs for each station are records of wind, ternperature, and ac curnu lat ed snowfall. Drawings on the right-hand side show the orientation and basic d irrie n s ion s of the

building and the nu mb e r and location of the snow gauge s on the roof. These detailed results, which are given in Figures 3 to 20, are su mrna r i ze d in Table I and in graphical equivalents in

Figure s 1 and 2.

B Station observations are su rnrna r i z ed in Table II showing the basic data received on each of the reports.

C Station observations are pre sented in a rnann e r sirrri l a r to the A Stations (Figures 21-27) and are su.rnrria r i.z ed

1D T able Ill.

Table IV pre sents the roof/ground load ratios for the large flat roofs at A and C Stations.

Figures 32 to 36 present sUITIITIaries of observations over the past seven winters.

Table V gives snow density and depth for A and C Stations for the tirne of ITIaxi:muITI depth on the ground for each of the past seven winters. Also given is the ITIaxiITIuITI depth and corresponding density that occurred over this seven-year period at each station. These densities are c o mpa r e d to the value 0.19 grn/ cc which was a s s u rrie d in the calculation of the NBC de sign ground load. The information shown in Figure s 32 to 36 was taken fr orn all progress reports on A and C Stations £rOITI 1957 - 58 to 1963-64.

RESULTS OF THE 1963-64 OBSERVATIONS

This discussion will centre on the c o mpa r i s on of ITIaxiITIuITI average and ITIaxiITIu:m roof loads with the ITIaxiITIuITI ground load

- 4 ..

and the NBC design ground and design roof loads.':<

ａｶ･ｲｾ･ Loads - All rna.xi mu m average roof loads were

well below the NBC design roof load, the ldrgest(56 per cent) occurring at Wabush Lake. The rnaxirnurn average roof loads were also significantly less than the maximum ground loads with only three roofs, two A Station roofs at Toronto and Kingston, and one C Station roof at Cold Lake, having rnaximum average roof

Joads app r oxirnating or exceeding the rnaxirnurn ground load.

Drift Loads - Only three roofs or 4 per cent of all roofs observed, had rria.xi rnu m 1'00£ loads, i •.e. drift loads, which

exceeded the NBC de sign value s (including shape factor s}, T'we nt yvn irie per cent of all roofs observed, however, had drift loads greater than the observed rnaxirnurn average ground load. These drifts usually occurred on the leeward side of arches or gables, along parapets, at the junction of split level roofs, at extending walls, at large chimneys and at any other object which would act as a snow fence.

Mo st of the roofs observed at B Stations illustrated drifting conditions and thus emphasized the role the wind plays in determining snow loads in exposed areas. In sheltered areas, on the other hand, the effect of wind is very small, and some very uniform loads were observed (e. g. on the garage in London, Ontario). The terms IIs h e l t e r e d' l and "exposed" are, however,

relative and difficult to define. They will be discussed in greater detail later.

MaxiITIUITl average roof load

Maxi rnu m roof load

(sometimes called drift load) Maximurn average ground load

NBC design ground load

NBC design roof load

The g r e at.e st average load over the entire 1'00£ recorded during the winter.

The greate st roof load recorded at any snow gauge during the winter. The greate st snow load on the ground recorded during the winter.

The 30··'year ground snow load given in Supplement No. 1 to the National Building Code (9).

80 per cent of the 30 -year ground snow load given in Supplement No. 1 to the National Building Code.

5

-The following pre sents a rno r e detailed discus sion of individual A and C Stations going fr o rn west to east.

A Stations

Inuvik, N. W. T. (Figure 3) - Snowfall fr orn October to April was 58 in., which appear s to be near the n o r rna l , The normal snowfall for Inuvik cannot yet be established as the townsite is relatively new but snowfall is comparable to n o r rna l conditions at Aklavik which is 50 rrri l e s west along the Mackenzie Delta.

The ratio of the roof to ground loads was lower than what would be expected from the low wind speeds. The rna xi rnurn hourly wind speed did not exceed 14 mph from the latter part of De c e rnb e r to the beginning of March, yet the average roof loads did not exceed 50 per cent of the ground load. The only occurrence of any significant drift loads was on the sloped roof E-3 residence where the load on some gauges equalled the ground load.

Winnipeg (Figure 6) - The ratio of the rna.xi murn average roof load to the NBC design roof load was again relatively low, even though the snowfall was 14 per cent above normal. High winds accompanied rno st heavy snowfalls and prevented average loads from building up on unobstructed roofs. The rna.xi rn a observed were 1 psf on the gable roof and 5 psf on the flat roof. Loads on the large flat library roof were at least twice those on the gable roof throughout the winter. An 8 in. high parapet wall surrounded the roof while a building (Main Library) 12 ft higher and 65 ft away protected the roof from the north and northwe st winds.

Toronto (Figure 8) - In spite of the heavy snowfall for this area (23 per cent above normal), the rnaxi rnu m average snow loads were only 3 psf (gable) and 11 p sf (flat). On the other hand, the drift loads were 5 psf and 22 psf, respectively.

Maximum loads occurred immediately after a heavy snowfall in December. Frequent thaws throughout the winter prevented any larger accumulation of snow.

Even though the flat roof (11 Douglas Avenue) is

classified as I'sheltered" due to its adjacent surroundings, snow accumulating on the roof was not uniform. Drift loads up to

6

-22 p sf occurred while other parts remained bare. This was basically due to the presence of the 2 1/2-ft parapet wall that accumulated high loads. Perfect shelter is highly improbable and any wind cause s drifts to form near par a pets ,

Kingston (Figure 9) - Ground loads in Kingston did not exceed 9 psf; the unusual snow drifts occurred along the parapets surrounding McNeill House with a maximum drift equalling 22 p sf , Because many of the gauges are located near the parapets, the average roof load calculated by adding the measured snow load and dividing by the number of gauges is larger than the true average load. The effect of this error in averaging is seen when, at the beginning of winter, the average roof loads exceeded the ground load up to 4 p sf , In view of the low loads, the high roof to ground ratios are not significant.

Ottawa (Figure 10) - For the third consecutive winter snowfall was below normal. The maximum average loads on the three flat roofs were low, while the drift loads exceeded the surrounding ground load for most of the winter. These drifts

occurred at the parapet on the DBR roof, on either side of the raised section of the sheltered Fairhaven roof, depending on which way the winds blew during the snowstorm, and near the large chinmey on the Davidson Crescent roof.

On the gable roofs, both average and drift loads were extremely low. The maximum drift encountered during the entire winter was 5 p sf , It appears that heat loss through the roofs played an important role.

Ste. Anne de Bellevue (Figure 11) - SnowfaIl at Ste , Anne's was well below normal and the maximum depth on the ground was only 10 in. Maximum loads as high as 29 psf, caused by an

accumulation of ice to a depth of 7 in.II were encountered at gauge

5 on the east wing of Macdonald College, however. The ice remained at this location varying in depth until warmer weather melted it

away by mid-March. The remainder of the roof was bare for the entire winter except gauges

6,

18 and 19 which had a few inches of snow at the beginning of January and at the end of February.

Snow on the flat-sloped west wing accumulated mainly at gauge s 8 and 9 which are adjacent to a higher gable roof. The maximum drift on this roof of 5 p sf was only 42 per cent of the maximum ground load, however, and the maximum average load only 13 per cent of the ground load.

7

-Montreal (Figure 12) - Unlike any previous progress year, Montreal and surroundings had very little snow - 52 in. rather than the normal 87 in. - the effect of which can be seen in both the roof and ground loads. Loads on both roofs were extremely small,

reaching a maximum of 5 psf on the flat roof and 14 p sf on the gable. Quebec City (Figure 13) - At this new A Station, observations were made on two large flat roofs; the Gymnasium and Pavillon

Vachon of Laval University. The Gymnasium roof has no vertical projections and is fully exposed to wind, while the roof of the Vachon PavilIon is situated between two higher roofs of the same building.

Snowfall for the December to March period was 117 in. (normal, 101 In , ] with a maximum observed ground load of 40 p sf , On the exposed gymnasium roof the snow load at any gauge point never exceeded 12 psf , which clearly indicates the large reduction in roof snow loads due to wind. On the sheltered Pavillon Vachon roof the average load was usually about 50 per cent of the ground load with drift loads of about 200 per cent of the ground load

occurring adjacent to the higher roof on the northeast side. Snow readings at gauges 10 and 12 were lower due to the influence of the ventilation system and should be changed for future observations.

Wabush (Figures 15 and 16) - An A Station was established in the new townsite of Wabush, Labrador, during the 1962-63 winter. Establishment of this new station seemed desirable as it is located in a region of very high snow loads and from which there is little meteorological data available.

The observations are made on two low-sloped gable roofs and one flat roof. All three buildings are located so they are fully exposed to the wind. Two of the roofs, however, are adjacent to higher roofs of the same building and thus are prone to drifts.

Two winters' observations confirm clearly that Wabush is an area of large snowfalls and and considerable drifting. The maximum ground loads were 50 psf in 1962-63 and 94 psf in 1963-64. Because of drifting the roof loads varied considerably. On the fully exposed gable roof of House No. 18 the average load was 9 psf and never exceeded the maximum 22 psf in 1963-64. On the other gable roof the lower portion of a split-level roof with a 4- ft step (Figure 28), however, there were drift loads of up to 62 p sf, The remainder of the roof was relatively free of snow (Figure 28). The third roof is the flat roof of the cafeteria

8

-building which is adjacent to a higher gable roof. The snow is blown along the gable roof and settle s on the flat roof. This caused drifts of up to 8 ft deep (127 psf) (Figure 29). As a result of the shelter provided by the higher roof, the average roof load of 49 psf was the highest of the three roofs, but still only 55 per cent of the ground load. The drifting that occurred on some other roofs at Wabush is shown in Figure s 30 and 31.

Halifax (Figure 18) - Although the snowfall was 86 per cent above normal, mild weather accompanied by high winds occurred frequently throughout the winter and prevented large accumulations of snow on the ground and on roofs. The maximum roof loads occurred at the base of the raised section (NRC Building), near the parapets (N. S. Technical College Building) and on the

leeward side of the gabled roof (Engineering Building). Even the maximum drift (12 p sf}, however, reached only 86 per cent of the ground load.

Gander (Figure 20) .. Considering the 156 in. snowfall, ground and roof loads were extremely small because of frequent mild spells. Strong winds up to 60 mph further reduced the accumulation of snow on roofs. Mild weather accompanied by occasional rainfall, especially in March and February, produced high densitie s such that small drifts (on the ground) in the

neighbourhood of 15 in. produced loads as great as 34 psf', On the roofs, maximum drifts of only 5 in. (10 psf) occurred on the leeward side of the sloped roof and just a trace on the flat roof.

Other A Stations .. The loads observed at the A Stations not specifically mentioned above (Edmonton, Saskatoon, Waterloo, Arvida, P. E. I. National Park, and Goose Bay) did not show any unusual features but all provided further evidence that roof loads are less than the corresponding ground loads. (See Figures 4, 5, 7, 14, 1 7 and 1 9. )

B Stations

B Station observers are only asked to record unusual snow loads. Most of their reports therefore related to roof drift loads equal to or greater than the ground load.

An interesting case of unbalanced loading in an exposed location in London, Ontario, occurred on the leeward side of an arch- shaped curling rink roof near a raised section of the roof.

9

-Drift loads up to 75 psf (4 ft to 5 ft in depth) accumulated on one side of the arch while the other side remained almost bare. Not only was the unbalanced load significant but the maximum observed load exceeded the NBC 1960 design load by 75 per cent. In contrast to this an unheated gable roof in a sheltered location, also in London, had an evenly distributed load of 15 psf over the entire roof, showing that the wind had little effect under the se sheltered conditions.

Other B Station observations concerned mainly accumulations of snow on leeward slopes, on lean-to's such as carports or porches, on lower parts of split-level roofs and on canopies.

C Stations

This year's observations at C Stations emphasize the earlier conclusion that large flat roofs in exposed locations accumulate verV

low average loads.

High local concentrations have occurred near the raised section on the mechanical equipment garage near the door housings of the cantilever hangar, on the flat roofs at the base of the arch hangar and on the canopies on lean-to roofs of the unit supply depot and cantilever hangar, while the centre portions of all roofs are usually bare except after a heavy snowfall.

GENERAL DISCUSSION

The qualitative factors affecting snow loads have been

discussed at length in previous progress reports. As the observations from the 1963-64 winter do not warrant a further discussion of the above factors the following paragraphs contain comments on some of the quantitative snow load factors.

Ground Snow Load

One of the basic elements of the approach of this survey of snow loads has been to relate the roof loads to the ground load. In the course of the survey, however, it has often been difficult to establish the true ground load for a station, due to drifting snow. The ground snow load varies considerably depending on the site of observations. This is illustrated in Appendix A by measurement taken at several sites in Ottawa during the same day.

10

-Ground Snow Density

The ground snow loads given In Supplement No. 1 to the National Building Code (9) are calculated on a.n as su.rne d specific gravity of 0.192 (12 lblcu It}, In these calculations, it was assumed that the rna.ximurn snow depth would occur immediately after a very large snowfall, and a considerable portion of the snow would be new snow with a specific gravity of about 0.1, thus justifying the low density. To the authors, however, it appears more probable that in rnany localities of Canada, the maximum snow depths will re s u It not mainly from a single very large sriow at o r m but from an a.ccurnulation of snow after several snow storms, thus leading to a s orne wh at higher density.

The average snow density that occurred for each winter maximum snow depth at 21 of the stations with four or more years' observations is 0.259

gml

cc with a standard deviation,

a,

of 0.047. The average snow density of the se same stations for the year when the depth was at a maximum was 0.262 (a

=

0.065). These figures indicate that during the years of greater snow

depths, the densities are not lower than average yearly densities but they are about the same value. These figures also imply

that the present NBC ground loads are somewhat too low, neglecting the influence of rain.

Another inve stigation was therefore made to compare the NBC ground loads to those measured in the survey of snow loads on roofs. For each year the ratio of survey ground load to NBC

ground load for each station was calculated and these figures were treated as though there were many year s of observations from a single station. These values plotted on normal probability paper (Figure 32) indicate that the 30"'year return period survey ground load is some 20 to 25 per cent higher than the NBC value.

Measurements of Shelter

The survey has clearly shown that roofs, or parts of roofs, that are exposed to the wind accumulate very little snow, whereas

roofs, or parts of roofs, that are sheltered are subjected to much heavier snow loads. In the past, the te r rn s " sheltered" and

"exposed" were used as a rneans of describing the effects of wind. In the survey these terms, used to describe the condition of a particular roof, were based ｯｾ judgements of different observers and, of course, were not expressed in quantitative terms. As the

11

-wind exerts such a rn aj o r influence on the loads, it appears very desirable to look for a quantitative means of expressing the amount of shelter.

The amount of shelter of a roof could perhaps be measured and expressed by a numerical value based on the following idea. The amount of shelter of a roof could be defined as the sum of the horizontal angles, measured in degrees, at which a line of sight, at roof level at the roof centre and sloped say 10 per cent upwards. inter sects objects in the near vicinity. The objects include parts of the building or neighbouring buildings, structures, trees and sometimes nearby hills. The greatest shelter will therefore be 360 and the least possible (fully exposed roof) O. These measure-ments could be made by locating a transit at roof level and

measuring the number of horizontal degree s where objects

intersect a line of sight sloping up 10 per cent. For the purpose of such measurements, the branches of single trees may have to be taken at some estimated value. If no transit is available. visual estimates would still be helpful. This idea has not yet been tried out.

Statistical Distribution of Average Roof Loads

The seven winters' observations of snow loads provide sufficient data for some initial statistical investigations to be made. As a means of reviewing the results to date and also as a help in developing methods of analysing the final results, various statistical distributions of the average roof loads were examined graphically.

The first relationship studied was the ratio of the maximum average roof load each winter at all the roofs to the NBC (1960) design roof load. To compare the data from different areas. the measured roof loads were divided by the NBC roof loads. The ratios were then grouped into intervals of O. 1 and plotted on normal probability paper (Figure 33) as outlined by Velz (10). The points, which follow the normal distribution (straight line) fairly well, indicate:

1.

On the average, the roof load having a chance of 1: 30 of being exceeded in a particular winter is approximately 50 per cent of the NBC de sign load.

2. The chance of the maximum average roof load exceeding the NBC design load during a winter is in the order of 1: 10,000.

12

-The next question studied was the ratio of the maximum average roof loads to the ground loads. For every A and C

Station roof each ye a rls maximum average roof load was divided

by that ye a r!s maximum ground load measured near that

particular roof. The roofs were separated into sloped and flat roofs, and the data grouped in declining order in intervals of 0.1. The points were again plotted on normal probability

paper (Figure 34). The se indications of the data are as follows: Flat Roofs

On the average, 50 per cent, 20 per cent and 6 per cent of the flat roofs observed had a maximum average roof load that exceeded 0.3, 0.6 and 0.8, respectively of the ground load in a particular winte r ,

Sloped Roofs

On the average, 70 per cent, 6 per cent and 1 per cent of the sloped roofs observed had a maximurn average roof load that exceeded 0.3, 0.6 and 0.8, re spectively of the ground load.

The above indication that there is less snow on sloped roofs than flat roofs should, however, be viewed with caution because:

(a) the roofs selected for the survey may not be representative of all type s of roofs nor give a correct average,

(b) there are fewer sloped roofs in the survey than flat roofs, (c) most of the sloped roofs are located in ex.f>osed areas and

are free of vertical projections, and

(d) many of the sloped roofs are heated but poorly insulated. It had generally been assumed in the survey that the ratio of maximum average roof to ground load for anyone roof is

reasonably constant over the years. This ratio of roof to ground load, however, has been found to vary from year to year. Thus, to determine the probable roof loads from (a) the ground load and (b) the roof to ground load ratio, the distributions of both

variable s must be known.

To inve stigate the variation of roof to ground load ratios on a roof during different winters, five flat roofs were selected -three at Ottawa and one each at Goose Bay and Gander. All of these

13

-buildings have been observed for seven winters. Each winter's rna.xi mu rn average roof load was divided by the winter's rnaxi murn ground load. The seven ratios from each of the buildings were then used to plot five distribution curves of roof to ground load ratios for a particular roof during different winters (Figure 35).

Although the points do not follow the no r rrial distribution too well, they allow the following indications. At a well-sheltered roof in Ottawa the rne an ratio was 0.67 with a standard deviation of only about 0.12. The other two roofs in Ottawa are partly sheltered and apparently due to this, their ratios are rnu c h rno r e variable. Their rrie an ratios were 0.43 and 0.54 with standard deviations of O. 13 and O. 15. Finally, for the two roofs at Goose Bay and Gander the fully exposed conditions resulted in low rne a n roof to ground load ratios of 0.14 and 0.08, respectively, with standard deviations of about 0.07. This s e e rn s to c onfi r rn the fact that rna xi rnurn roof to ground load ratios vary considerably fr orn year to year for a given roof and that the application of ratio observed in one winter to the 30-year rnaxi rnurn ground load should be considered further.

Instead of de te r rrrining the design load fr o m each winter's ground load and the roof to ground load ratio, the design load could, in principle, also be established solely on the roof load rne a s u r ernerits , except, of course,for the fact that there is insufficient coverage of Canada by A and C Stations. The roof load rne a su r e rne nt s over a nurnbe r of year s could be used to arrive at an e xt r e rne roof load such as that which is expected to occur on the average of once in 30 years. This roof load for a particular kind of roof could then be c ornpa r e d with the 30-year ground load for the particular station as found in Supple rnerit No. 1 to the National Building Code (9) to establish ratios for c ornpa r i s on with other stations.

To illustrate this rrie th od two flat roofs (Gander, Goose Bay) were selected because they have been observed for the entire seven winters. The results were plotted on n o r ma.l probability paper (Figure 36). The average roof load expected to be exceeded on the average of once in 30 years was 6 psf at Gander and 17 p sf at Goose Bay.

The NBC (1960) ground loads are 62 psf at Gander and 103 at Goose Bay. The roof to ground load ratio could then be taken as 0.10 and 0.17.

14

-ground load, -ground loads and e xt r e rne roof load can be c ornpa r ed to the e xt r e rne ground load predicted fr o m the rne a su r e me nt s taken for the survey. This rriethod would have the advantage of c o rnpa r irig the loads over the s arne period and would thereby take into account the occurrence of a period of either unusually large or s ma l l snow conditions. The 1:30 ground load graphically d e te r rni.n ed fr o m the seven years of observations at Gander and Goose Bay were 78 and 114 p sf , Thus, the ratios would be 0.08 and 0.15 instead of 0.10 and 0.17.

INTERIM CONCLUSIONS

The 1963-64 observations have substantiated rno st of the irrte r irn conclusions of previous reports. These conclusions can be restated here as follows:

1.

The average snow loads on roofs are less than the load on the surrounding ground.

2. The arnount by which the average snow load on the roof differs fr orn the snow load on the ground (roof to ground load ratio) depends p r irna r i.l.y on the degree to which the roof is sheltered. The effects of shelter are, however, difficult to predict exactly.

3. Whereas well-sheltered roofs have ratios up to about 0.9, nearly all exposed roofs have ratios of less than 0.6 with rriarry well-exposed unobstructed roofs exhibiting very low ratios.

4. Very heavy snow loads (drifts), which frequently exceed the load on the ground by a large factor, are found in any roof area of localized shelter, the magnitude of the load being dependent on, among other things, the shape of the building, the snowfall, the size of the roof area which is "contributary", and the height of the localized shelter. A first step in providing designers with "shape factors" to take into account probable ac curnuIation s of snow due to drifting and other influences has been taken by

fo r mul ating "Coefficients for Snow Loads on Roof s " which are published in Suppl e me nt No. 3 to the National Building Code, 1965 (11).

5. Because of the c ornpl e xi.ty and variability of factors affecting snow loads, a statistical approach to the d e te r rrrin a.ti on of design roof snow load b e corne s necessary.

15

-6. The 30-year ground loads determined from the survey measurements appear to be 20 to 25 per cent greater than the NBC 1960 ground loads.

REFERENCES

1. Allen, D. E. Snow loads on roofs, 1956-57. A Progre ss Report, National Research Council, Division of Building Research, DBR Internal Report No. 134, Ottawa, January 1958.

2. Allen D. E. and C. J. 'I'u r k st r a , Snow loads on roofs, 1957-58. Second Progress Report, National Research Council, Division of Building Research,

DBR Internal Report No. 163, Ottawa, November 1958. 3. Thorburn, H. J. and B. G. W. Peter. Snow loads on roofs,

1958-59. Third Progress Report, National Research Council, Division of Building Research, DBR Internal Report No. 184, Ottawa, November 1959.

4. Watt, W. E. and H. J. Thorburn. Snow loads on roofs, 1959-60. Fourth Progress Report, National Research Council, Division of Building Re search, DBR Internal Report No. 204, Ottawa, November 1960.

5. Scott, J.F. and B.G. W. Peter. Snow loads on roofs, 1960-61. Fifth Progress Report, National Research Council, Division of Building Research, DBR Internal Report No. 228, Ottawa, November 1961.

6. Hebert, P', A. and B. G. W. Peter. Snow loads on roofs, 1961 .. 62. Sixth Progre ss Report, National Research Council, Division of Building Research, DBR Internal Report No. 260, Ottawa, January 1963.

7. Allen, C. M. and B. G. W. Peter. Snow loads on roofs, 1962 .. 63. Seventh Progress Report, National Research Council, Division of Building Research, DBR Internal Report No. 279, Ottawa, November 1963.

8. National Building Code of Canada, 1965. National Re search Council, Associate Committee on the National Building Code, Ottawa. NRC 8305.

9. Climatic information for building de sign in Canada.

Supplement No.1 to the National Building Code, 1965. National Research Council, Associate Committee on the National Building Code, Ottawa. NRC 8329 •.

16

-10.. Ve l z , C. J. Graphical Approach to Statistics. Water and Sewage Works, Vol.. 99, No.4, 1952.

II.. Structural information for building design in Canada.

Supplement No. 3 to the National Building Code, 1965. National Research Council, Associate Committee on the National Building Code, Ottawa. NRC 8331.

LOAD IN LB1SO FT (1963 -64) No C STATIONS I LANCASTER 2 COLD LAKE 3 WINNIPEG 4 NORTH BAY 5 TORONTO 6 OTTAWA 7 GANDER No A STAT IONS I INUVIK 2 EDMONTON 3 SASKATOON 4 WINNIPEG 5 WATERLOO 6 TORONTO 7 KINGSTON 8 OTTAWA

9 STE ANNE DE BELLEVUE 10 MONTREAL

II QUEBEC 12 ARVIDA 13 WABUSH

14 PEl. NAT IONAL PARK 15 HALIFAX 16 GOOSE BAY 17 GANDER

.:

\

IU

j

Ｌｕｕｾ ｾ

J

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ｾ

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J'lii' \-'

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I-A GROUND LOAD (MAXI

/J

/ LEGEND

ＴﾰＱＳｾ

30 Ｒｾ 20 ｉｾ 10 ｾ <, <, " "

/

... . ... /

--.

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11

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1

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.

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_{_r} - .. __.. I 1l.4-A _ .._ ..｟Ｎｾ｣ＮＮ AVG ROOF LOAD (MAX)

ｄｾ

FIGURE I

A

a

C STATION LOCATIONS AND THEIR AVERAGE ROOF AND (MAXIMA OBSERVED 1963/64)

I I ｾＱＳＰｎｖＹ AV8 3S009 ｘｖｾｬｬ｜ｉｈ )lI:IVd l\INOIlVN '1'3'd Hsn8VM VOIIII:IV 3383no I

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ｾＭＭＭｾL I _ I l\IHIlNOW 3nll31138 30 3NNV US VMVllO N01S9N 1)1 OlNOI:IOl 0011:1UVM 93dlNNIM NOOIV)lSVS NOINOW03 )lIIInNI VI z a ... < ... VI < ... < VI o < a - ' o 0 00 ' 0 oN - ' o o - ' o 00 o 0 0 ' 0 ... N o U/81 NI OV01

u:

en

a: o Cl: o ...J NUMBER INDICATES GAUGE LOCATION OF MAXIMUM TIME (DAYS) MAXIMUM ON CANOPY OR LEAN - TO ROOF ETC. MAXIMUM} LOAD ON

AVERAGE MAIN ROOF

MINIMUM

LEGEND FOR FIGURES 3 TO 27 INCLUSIVE

40. + + -federal Bill). AllMaxima iIt#\ ROOf DESCRIPTION

I

2011' --_... ---_.... e---" 40 ｾＭＭＭ

•

o '"o 20 / -..I , '-- _\ federal Building ｾ / ' ｾ \ ｨｾＳＰ /20 ' - I

- - - 1

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IExi»'ed, Hoilted, In,uliltedl

20 Ｍｾ --40 --,, r - --../ o ｾＭＭＭ

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/

<,

.,.

4' --I I '5

_tii

i IZ

V

ＱｾＧＲ 3. ｾＧＷ I. _--j

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7' .10 " /8 .B ｾＮ ______1i

L-

IB I _-J

SNOW LOAD OBSERVATIONS ON ROOFS

+--fExlXlsed, Heated, Insulated 411l

(Sheltered from South,LowHeatl

Home ECOnOmiC\Annex ｾ / ' D ｾ \

ｑｾｊ

SNOWfALL -<tb'emberｾApril) Normal 196364 - 40" FIGURE 3 ---J YEAR, 1963/64 LOCATION,INUVIK, N.W.T. APR IL I I I i MARCH FEBRUARY JANUARY DECEMBER NOVEMBER OCTOBER ::l ＴＰｾＭﾭ :E ｾ u u '"

. _ . _ 1 -40 1 ' -Mining StoreShed go ｾＭＭＭＭＭＭＭｪｬﾭ I

.::::..-I

I !

ＯｾＭＭｾ

---l

ｾｾｾ --- _ ..+ - - - 1 -_._----ROOF DESCRIPTION

Mining Store Shed

I..- nC,,"

1

EBB

'

7'-J

.. ·2 " . /6' -3 7-.4 8. r-: (Sheltered, Unheated Bldg. I ---+---+.--- t -20 1 - - - -T • yA Administration Bldg, II N

0

I- 74' -J , ｾ＾ａ , ! + '1 '4- 7' 4';"1 • 2 '7 ｾ

.

j- • J .,;

,

.

---- - ._._- _._--- _._---_._---+_._---_._---1 4 _, ...ＮＬＬＭＭｾ -,- - - - - , ....

_

-Administration Bldg.

---r---I =-- - ---40

NOVEMBER DECEMBER JANUARY FEBRUARY MARCH

SNOWFALL (November - Marchi Normal 1963-64 39" 33"

FIGURE

4

. - - - 1 -- --- --- -1---1 I

i - l

I I

ｪＭＭＭＭｾＫＭｾ

, N W+E S 40 o 40 50 32 ｾ 120 ---+Il---i---;; i

ｾ

80 -

----f----! I -ﾫｾ c · z"-«::;0 ｾｾ ::;0>--40 -o z ｾｾ

>-"-=

i 20 -c °c ｸｾ «"-:2'",

-SNOW

LOAD

OBSERVATIONS

ON

ROOFS

YEAR 1963/64

LOCATION EDMONTON,

3'

-.

!ＲＱｾＨＬＭＧ !

'-'-'''--__,_-=--' --l ROOF DESCRI PTION

ＭＧｾ

(Exposed, Heated, In sulatedl

N OutclJor <) Test Station . /

.

ｾ .7 -j

0-'/3'

.7 e ,5 .8 ₇₄ _-l • .3 • z; • ,9

_•

30 314 Lake Crescent I':J 133 - lOlth SI. <).

(Exposed, Heated, I nsulatedl

40 ｾ 0 20 «

=:

20 40 -Outroor Test Station 40 20

NOVEMBER DECEMBER JANUARY FEBRUARY MARCH

o 80 >-« ::J

'"

::J U 40 u « o o 40 Z ｾＺｉＺＮ >-0-=:i 201+ --+li\--« 0 0 ｸｾ «0-ＢＧｾ 0 - -50 SNOWFALL lDecember - MarchI Normal 1963 - 64 26" 21" FIGURE 5(a)

SNOW LOAD OBSERVATIONS ON ROOFS YEAR: 1963/64

ROOF DESCRIPTION NRC Lab. '---- ｾＭｾｌＮＭＭＭＮＮＮＮＮＮＮｊｊ I NRCLaIJ. 40 20 ,ｾＭＭ '217 1 - - - ..,, I

__

Ｔｾ

-f7--g'--

---==-=:2

:----

3B 1 o « o _. - + ---Detai i A (Exposed, Heated, I nsulatedl

40

Gymnasium

Gymnasium -'2

20

-8 _4- re z

NOVEMBER FEBRUARY MARCH

Exposed, Heated, Ventilated 'l' Parapets ｾ 120 u->: o z V> 0 80 "' >--c ｾ =>• :;;: => 40 u u <

"

,-0 Z _ : I : >: . c, >-ｾＺ［［Ｚ 20 -c SNOWFALL 0 0 x"' (December - Marchi "' <,,-:;;:V> 0 50 Normal 1963-64 26" 21" >- 32 ｾ - u-<c 0

FIGURE 5(b)

SNOW

LOAD

OBSERVATIONS

ON

ROOFS

YEAR: 1963/64

- - - .9

.4J-;-1

.,IJ 05 2 • ."!

ｾＡ

.7 •co I'-l

ｌＭＭＭｺｺＭｾ

South Wingof Library ROOF DESCRI PTION

dnL 12' Above Roof , / ! I N

?

'I ＭＭＭＭＭｆｾ I 12

1

-i--+---+--7 I ! I South Wing i of Library 20 - - - -

t--40 1---ｾ 'Jt,-'" 80 -« o

Exposed, I nsulated, not Ventilated, Unheated Air Space

60 - --- - - - 1 - - - 1 - - - + - - - 1 4 0 -20 - - -

--1-

---Agricultural Eng. Bldg.

ｾＱＭＭＭ

ｾＧＭｾＧｾＧＺＭＡＺ

----:>

/ K.t

'0

Agricultural Eng. Bldg. / 43 "-

,rr--.,

I 205 • 13 .17\

1/

07 co •

1

0

j

.14• 9 .3 5. .11 [ｾ • I 4' ｾ［ • 10 .2 J • _---l 5' Above Roof F l New CropResearch Bldg. Sheltered Attic Unheated, Ventilated, Insulated

NOVEMBER DECEMBER JANUARY FEBRUARY MARCH

--- - ----+- ---+ ＭＭＭＭＭｾ 80 -SNOWFALL (November - March) Normal 1963-64 43" 49"

FIGURE

6

-:«

ｾＭＭｬＭＭＭＭＭＭＭｬｲＭＭＭＭＭＭＭＭ 40 1 - - - - f---:::> :2' :::> u u -c o J I , I j ----'"---I- - ｾＭ - - -

-+-+- ---"- -

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ｾ ｾ

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'V

v

V

ｾＧ

V

vv

v

Ｇｾｶ

o -40

SNOW LOAD OBSERVATIONS

ON ROOFS

YEAR 1963/64

254 Sunvlew ROOF OESCRIPTION '> , Ｎ｟ｾ I

Ｒ｢ＧＯｾＧ

ＬｾｾＢ I r ｪＮｊｾ ,

(Heated, Insulated, Exposedl

I I

--- ---+

. i 254 Sunview i ----l 20 - ---40 3 7 Main Eng. Bldg.

--f-

- - - t I / \ 7 7 3/:. \ 917 : ｾ｜｟ＭＭＧＢＮｧ［Ｚｩｺ ---,

A

ｾＮＭＮＭＭＭＭＭ . i I 40

-it ₂₀ 0 <I: 0 ｾ 'J 8 7 1 7/ - r:;, ｾ 144

I--(Heated, I nsulaled, EXlXlsedJ

1 - 1 - - - -_....t.

t

:--.8

-+--Ｎ

ｾ

_{". . "\ ....ＺＭＮＮｾＭ･}

Ｗ ﾷ ｾＵ

7. < - - - b - --- , Eng. Bldg. 20 40 .4 • '7

.

ｾ /3/-0 ' .7 .3 B-B Normal 1963-64 45" 48" FIGURE 7 ::-L.,L-

r

SNOWFALL (December - March) Engi neering Bldg.

. (Healed, Insulated, Exposedl

-z<)

MARCH ," NOVEMBER z ｾ ｾ <I: ｾ :;: 0 z 80 V> 0 ｾ ... :3 :::> ::;' ₄₀ :::> u u <I: 0 0 40 N z _ :I: W+E :;: . 0.. >-S ｾＺＺ［Ｇ 20 <I: 0 0 ｸｾ <1:0.. ::;'V> 0 50 ->- ₃₂ Ｍｾ <1:' 0 zo.. <1:::;' ｾｾ ::;'... -40

SNOW LOAD OBSERVATIONS ON ROOFS YEAR: 1963/64

ROOF DESCRI PTION ｾ 21 Douglas Cres <.-J ｾ /7 \

ｃｄＵｾ

Ｚｦｾ｟ＮＧ

..,

ｾｾ｟ｴ

37 3."' - (, ---1

'-B'."

0'"

qo .1J, -4 ·"Go ' I 3 I I ｾＷ • L O • ! II Douglas cres Sheltered Bldg. Heated Allic Unheated Cei ling Insulated

- -. -+---ｾＭＭＭＭＭＭＭｾＮＮＮＮ ｾＧＬ 21 Douglas Cres 1 ! 80 60 40 20 N '1j,- ₀ '" -c ｾ 60 --40 ._-20 0

(Sheltered, Heated, Insulated)

NOVEMBER DECEMBER JANUARY FEBRUARY MARCH

FIGURE

8

SNOWFALL !December - March) Normal 1963- 64 49" 59" I

j

I !,--"

---

-+--20 80 . -40 «"-0")

SNOW

LOAD

OBSERVATIONS ON

ROOFS

YEAR 1963/64

LOCATION TORONTO, ONT.

I

j

ｾｾ ＭＭｾＭＭＭＭＭＭｲＭＭＭ

I

!

ROOF DESCRI PTION

40 - --'-I

o

N , I H" 40 .1_ oj .,;,

'0

I

ＮＸＷｦｬｾ

I- --- ---, McNeill House

,-

01 0 4 70 i 3,;, oZ _·5 ｾ 0 26 Edgehill Exposed Insulated Attic not Ventilated Attic not Heated Bldg. Heated Parapet 2'6" /4

V

40'

ＷｕＱｾＮＧ

i

l

Sheltered .,JL,.

Attic not Heated V

Bldg. Heated rN Insulated MARCH FEBRUARY

.---_.+-

- - - j I

-i-I JANUARY McNeill House All Maxima 'I at#1 f---I i 'r NOVEMBER DECEMBER 20 20 40

FIGURE

9

Normal 1963-64 64" 50" SNOWFALL lDecember - ,March) - ＭＭｾＭｉＭ N W+E S - - ｾ

f----I

--J

20 o 50 40 BO--o 40 - 40 j 120 <_u, ;: o z '" c ｾ ... < ｾ ::::> lIE ::::> u u -e c Z . _ : I : ;: . C. >- . ｾＺｅ < C c ｸｾ <c. :E",

SNOW

LOAD

OBSERVATIONS

ON

ROOFS

YEAR; 1963/64

LOCATION: KINGSTON, ONT.

ROOF DESCRIPTION

Davidson Cres.

Exposed Unheated Air Space Ceiling Insulated 14"1 Heated Bldg. Flat:10'to Eaves • 7 54' i

-.l

L----"'-'---i

-Oz--B ｾ 10 .'" 5· .2:5 4 !---,

----+

I Davidson Cres. All Maxima I at #6

---t--I 6 20 40 - - - -j ; ·9 :5 • • /2 .6 .10 4. .7 I • • 1/ .5 .8 2. SNOWFALL INovember - Marchi Normal 1963-64 83" 46"

FIGURE

10(0)

Fairhaven Way 9 • ": 5' '>-: _{• II} 3 . • 7 2 • 4· 12 .10 .,;, _j Hｾ II ｈｾｾ

(Sheltered, Heated, I nsulatedl

(Exposed, Heated, In sulatedl 40A Barker Blvd. n

--z-<)---.

1-)

==--MARCH ｾＭ -,--- -,--- -,--- -,--- -,--- _/ ｟ｾ｟］ＢＧＭ］ｾ］］Ｍｅ N

w-t

E S NOVEMBER 20 20 40 40 c « o _ _-lL z :; « ｾ ｾ 0 Z '" c 80 ｾ ... :3 :::l ::0 :::l ₄₀ u u « 0 -c 40 z:i ｾｯＺ >- . --,::0 « 20 c c ｾ ｸｾ «Cl. ::0'" 0 50 >--c c ZCl. «::0 ｾｾ ::0 ... -40

SNOW

LOAD

OBSERVATIONS

ON

ROOFS

YEAR, /963/64

ROOF DESCRIPTION I i I

ＷＲＭｂｩＺｏｾｾ

i

1---\----

+ - 1---

ｾＭＭＭｾＭ

I i ...

J

I ! _ - - ' t- / I ....i_ .... - i"'" /

j

l - - - _ ..- i, i ' .../ . '<'""> I ] .. [:::740 Barker Blvd,

'0

Q

.i : r---30'--""

ｾ

'8'".

T I ',24.7 7. 10 , - 2 4-L ｾ ./ 3. IExpcsed. ｈ･ｾｴ･､Ｌ Insulated2") 40 20 40 ;-0 20 <I: 3 I

I

+-- - -

---t-I 40 Barker Blvd. I - - -.- --- ! I i I -- - - - + - - ----I I ---t---.+

---,;

--

,

I - , I , / 4== 72 Bishop Blvd. I ]

<>V

Q

1---30'----1 T . .

I:Z4'85

7. 10 , - 2 4--iJ __i

3-IExpcsed, Heated, Insulated2"1

<>

N

I Exposed, Heated, Insulated) 40 20 I -, z

<)----ｺｾＮ

r:

DBR I , }2 ..L '-,-,72' '-1 T . f ;, 3. 4" · 4 5 6· ·7 _L3 ｾＮ • lO NOVEMBER MARCH z ｾ ｾ <I: ｾ ;;:: 0 z V> ₈₀ 0 ｾ >-:3 ::> ::1' ₄₀ ::> u u <I: 0

,-0 40 N Z _ : I : W+E ［［ＺＺｾ >- _S ｾＺＺＱＧ 20 <I: SNOWFALL 0 0 ｸｾ INovember - March) <1:,,-::1'V> ₀ 50 Normal 1963-64 83" 46" ':. Ｍｾ <I: 0 z"-

FIGURE

10 (b)

::;::1' ＺＺＱＧｾ _{- 40}

SNOW

LOAD

OBSERVATIONS ON

ROOFS

YEAR, 1963/64

LOCATION, _OTTAWA,ONT.

ROOF DESCRIPTION

40

Poultry Bldg. (West Wing)

PouItry Bldg. (West Wingl

20 o < o I ' /s ... , _ 8

1

(Exposed. InsulatedVentilated. Heated)

Poultry Bldg. (East Wing) 40 FIGURE II SNOWFALL (November - March) Normal 1963 - 64 95" 52" Exposed. Insulated Attic Ventilated Attic not Heated Bldg. Heated

I ' ,

£Al/t;;";?/,y'! 'A.,.J/27'

ｴＭＭＭＧｾＭＭＭＭＭＭ ----.,'----MARCH Poultry Bldg. (East Wingl ;3 5 -- ----;-- --- ＮＬＭＭＮＭＺＺ］ｾ ...!.._=====I===O:: NOVEMBER 20 -20 :::: <

...

;: o z VI 80 o W 0-<ｾ => ｾ 40 u u < ｾ

-

...

<0 o Za. <:< Ww :<0- -4 o z . _ : I : ;:a: >- . ｾＺ＼ < 0 0 ｸｾ <a. :<VI 0 5 0 t - - - ---+--- ---+

-_._---LOCATION:STE. ANNE DE

BELLEVUE, P. Q.

ROOF DESCRIPTION

11771 O'Brien Blv .

All Roof Parts

Exposed Heated Insulated / "'--'---"-_--'--_.!.J. L 1--- 32 ·7 S _ｾ 11771 O'Brien Blvd. 8439 Berri SI. L--- 55

-",. / . _2'Parapet ,g. 4" Parapet ₃₀ 5· 2· + h·25' -7. 4. 3.

-z--Q---

- 25' -+ 80 60 40 20 ;;-0

""

0 ｾ 60 40 -20

IExlXlsed, Heated, NotI nsulatedl

NOVEMBER DECEMBER JANUARY FEBRUARY MARCH

80 :::: 120

""

"-ｾ o z '" So >-ｾ "

-""

0 ZC-"":;; ｾｾ ::<''''" -40

SNOW

LOAD

OBSERVATIONS ON ROOFS

SNOWFALL INovember - MarchI Normal 1963-64 95" 52"

FIGURE

12

YEAR, 1963/64 LOCATION MONTREAL, P.Q. I ---1--- __ｾＭｃＢＧＺＺＺＺ｟｟Ｍ］ＭＭＭ -40 0 4-0 _N W+E 20 S o Z - : I : 5:0.: >- . ｾＺ［［

""

0 0 ｸｾ ""0-:;;'" til'?ＮｊＧ［ｏｉＭＯｾ

ROOF DESCRIPTION 40 Ｔ］］］］Ｍｾ］］］］ＺＺＺＺｾＭＭｾＭｾＭＭＭ Gymnasium

.

o J. ---; B ＭＭＯｾｾＭＭＭ

1"7

",-I'

.

_"

ｾｉ

I I ｬＬｾﾷ｟Ｑ .:- ｾ

f---7 7 4 Gymnasium 20 A '---, r-r-' fO. • 7 4· I . II • .8 5. 7. 12. . j 0. j . ----J> -Exposed, Insulated, Heated, Non Ventilated

,r

1

2 2 2 __ 2 I

----I

ｦＭＭＭＭＭＭＫｾＭ I Pavilion 40 - ----80

- '!Io-e « 0 60 ｾ I ＭＭＭＭｾｩ

+

Ｍｾｉｉ

vscnon - - -

r

I I 11" -

I

ＡｉｾＭＭ＾ＫｾＭｾＭＭＭｲＭ

/ I '

ｾ

_ _2-,-0+

-=1

_--.:-f_ _.J-'-_ _

ｾ

NOVEMBER DECEMBER JANUARY FEBRUARY MARCH

z

ｾ ₁₂₀ ---

---,--ｾ « [ ｾ :s: 0 Z '" 80

-r

e ｾ I -:3

.t.

::J ::;; 40 ::J U U « 0 e 40 _N Z i:I::. W+E >-0-］ｾ 20 S « e e ｾ ｸｾ «0-::;;'" ₀ 50 ｾ ﾫｾ e Z o -o::;::;; Ｚ［ＺＺｾ -40 -

ｾＭＭＭ

I

Exposed, Insulated, Heated, Non Ventilated

SNOWFA LL lDecember - March I

Normal 1963-64

101" 117"

FIGURt: 13

SNOW

LOAD

OBSERVATIONS ON

ROOFS

YEAR 1963/64

i, -e, I

----L---+-I I

-j

ROOF DESCRIPTION Bldg.No. 60 60

.-c ₄₀ < 0 --' 20 - --t---i " I ; Alcan Bldg. no.601 I

----t---l

---t --

----I

'"

, , '

ＬＭＭｾＭｬ

! ', ,, I 4\

.&-

,3 A.2 , I 'II Ii •/0 I}OI.9 , .+ .!J Section A-A

r--==-J

}78r

NOVEMBER DECEMBER JANUARY MARCH

ExfXIsed. Heated, Insulated

20

z

--' 120 --' 1 < ｾ ;: 0 z '" 80 c ｾ 0-< --' :::> ::;; ₄₀ :::> u u < o c----,nf z . _::t: ;:a: >- . --'::;; < C c ｸｾ <0-::;;'" o 50 32 ZO-<::;; ｾ ｾ -40 - - N , W-L, E - - - j---I I t -SNOWFALL I December - March I Normal 1963-64 91" 88"

FIGURE 14

SNOW

LOAD

OBSERVATIONS ON

ROOFS

YEAR: 1963/64

i 60 Ｍｾｾ ｾＭｾＭｾ fbuse 18

!

I ｾＭＭＱ ROOF DESCRIPTION 40 ｾＭ - -ｾ 10 ＭＭｾＭ ｾＭＭＮ - I Iv-, /" , ... -,I ' ... ---... -J. 1-_ _ " -ＭｾＭ

,

ｾ , -ｾＭ -ｲＭｾＭ 42ｾＭＭＭＭｪ fbu"1 8

ｾｾｌｬＢｃｮｽＧ

f ｌＮｾＭＭＭＭＭｬ __ｾJL ｾ｟ｾ ｾＧＭＢＮ

-Ex!"sed, Heated, Insulated

- - ｾＭ Ｍｾ ｾＭ -House9, 11 60 -ｾ ＭＭｾｾ ｾｾＭ -40 10 I II / \ " -, ! I \ I I ＭＭｾ _{/ ' " "<,1 \} \ ! ｾｵｳ･ 9, 11 ＿ｾＲ I _J 4 L

O

Ｍｾ ;>41 I

h

*f '"

0 j _·8 ..1 f,.- _.,,'-1 ._-- .., ｅｸｾｳ･､Ｌ Heated, Insulated 4

OCTOBER NOVEMBER DECEMBER JANUARY FEBRUARY MARCH APRIL

ｾＭＭｾＭｾｾＭＭＭｉＭＭＭＭＭＭＭＫＭＭｾＭＭＫＭＭＭＭｴＭＭＭＭ ｾＫＭＭＭＭＭｦＭＭＭＭ ｾＭＭＭＭＱＭＭＭＭＭＭＫＭｾｾ 1961-63 t«lrmal ＭＭｾｾｦＭＭＭ

ｾＭＭｌＭＭＭ

ｾＭｾＭＫｾｾｾＭｾＫＭＭｾＭ｟Ｎ ｾ I ｾＭｾｾｾＭＫｾｾｾＭ =: :: 110ｉＭＭＭＭＭＭＭｾＭ < ｾ o z VI 80 f---. o ｾ < => ｾ 40f + -u u < I

ｦＭＭＭ［Ｚ［ＭＭＮｾ

ｉＭＭＭＭＭｲｾ

ｾ ｾ

10

ｾＭＭＭＭＭＫＭＭＭＭ

< 0 0 ＾＼ｾ <0. '"ｾ n SO ::. < . o Zoo 0I f -< " , ｾｾ ＢＧｾ -40 FIGURE 15(0)

SNOW LOAD OBSERVATIONS ON ROOFS

YEAR, 1962/63

ROOF DESCRIPTION 1---j

•

Cafeteria - - - -I' "I 120 Ｍｾ ---'----._---- -

-

-¢-100 - ;;-0 80 ｾ =: 60 e--ao 20 ...0.. 1 I -/ --\ ＫＭＭＭ｟Ｎｾ｟ＮＧＧＧＧＬＮＮ ..ＺｾｾｾＭ｟Ｏ \ ｾＭＭ \ i

ｾ

--- -r--- j---=-=

-A - -A (ExJXlsed, Heated, Insulated)

- - - f - - - + - - - Normal 1962-63 APR IL + -MARCH FEBRUARY +++ -___ｾＭＭＭＭｬ

-+

-+__

ｾ JANUARY - - - -ＭＭＭｪｾｾｾＭＭ DECEMBER NOVEMBER

I

ＭｾＭＭＭＭＭＭＫＭＭＭＭＭ

I OCTOBER

----I-

+

80 I--

ｾ｟

L

I

l---+---• => ｾ 40 u u -c. ::: \20 ｾ

..,

o z C dO z -_ I "'0: >-ｾ >-ｾ 20 1----Cc ｸｾ '"'''-::e", ＭＭＭｽＫＭｾＭｾｾＭＫＭ z"-ｾＺＺ･ ｾｾ -40 FIGURE 15(b) SNOW LOAD OBSERVATIONS ON ROOFS

YEAR, 1962/63

4 0 - ---t---I-t>use 18 ROOF DESCRIPTION

ｉＺｾ

_•

1/4

Expose« Heate« I nsuteted

Exposed,Heate« Insulole<!

I-t>use9, 11 APRIl MARCH ＫＭＭＭＭＭＭＭｪＭＭＭＭＭＭＭＭＭｾ FEBRUARY JANUARY DECEMBER NOVEMBER OCTOBER 20

-

₀ 'io-a 100 -a: a 80 60 : 120L -

---T'

---l -

---+--ｾ i I I

ｾ

80

---i

---'---i

--I

ｾ

I ':,-

!

Y :

_I--+---j--SNOWFALL tNovemer - Marchi Norm,l 1963-64 105" FIGURE 16(0) SNOW LOAD OBSERVATIONS ON ROOFS YEAR 1963/64

10 :::: 110 :2

'"

o z BO

OCTOBER NOVEMBER DECEMBER JANUARY FEBRUARY MARCH APR IL

ROOF DESCRIPTION

Cafeteria

- _ｾＭ

5l

A-A

IExIllsed. Heated, In,ulatodl

40 o ［［ＭＭｾｾ z ［ｾ ＾Ｍｾ ::::i 10 "'"0 0 XW ＼ｾ ＬＬｾ 0 50 -40

SNOW LOAD OBSERVATIONS ON ROOFS

SNOWFAll (November - March) Normal 1963 -6' 105" FIGURE 16(b) YEAR 1963/64 LOCATION WABUSH, P.Q.

Dalvay: Central Stores FIGURE l7(a) Normal 1963-64 91" 140" SNOWFALL (December· Aprlll ROOF OESCRIPTION

(Sheltered from theNorth, Insulated, Unheated)

Dalvay: Residence ｬｅｸｾｳ･､Ｌ Heated, Insulated) N

r

7

.-

; .;; ｾ ; ; ｾ I

r

ＴＰｾ 41

L

APR IL JANUARY \ i I I I ＭＫＭＭＭＭｾＭ ---l-I Oalvay,Residencj W NOVEMBER OECEMBER OCTOBER

+---1-I 20 40 • 0 80 -e; ｾ 60 40 20 :': 20 -e;

"

0 z ｾ ₈₀ 0 -e; => 40 ::E => u U 0< 0 0 40 ｾＺｩ "0: >- . ｾＺＺｅ 20 ｾｯ ｸｾ ｏ＼ｾ ＺＺｅｾ 0 50 >-0<0 0 ｺｾ 0 ""'::E ｾｾ ＺＺｅｾ - 40 i 80I + t t -Dalvay I I Ic••"

'''0

ＱＭＭＭＭＭＭＭＭＭＭＭＫＭＭＭＭＭＭＭｴｅｾ

I: II

' n

' Ii I

i

i

I I i T

I

.

_ - - + - _ 1 I -r-:-

ｾ

SNOW LOAD OBSERVATIONS ON ROOFS YEAR, 1963/64

LOCATION, P.E.I. NATIONAL PARK

tOO

-

.-0 80

..

ｾ 60 40 20 ROOF OESCRIPTION

stanhope: Registration Office

----'2:+-39 I

/0[1

. I,2 4,j ' 'J ." 2J

I'

I

9[[

_ｾ

(Sheltered from theEast andWest, Insulated. not Heated)

ｾＬ

:: I

OCTOBER NOVEMBER JANUARY FEBRUARY MARCH APRIL

120

ＭＭＭｾＭＭＭＭＫＭ

-e:

"

ｾ ｾ 80 -e: =>

'"

40 => u u -e: 0 0 40 _N 2' -" W+E ＬＬｾ >-ｾＧＢ 20 S -e: 0 0 ｸｾ

..

ｾ ＢＧｾ 0 50 ': ［［Ｚｾ o ' ｚｾ ｾｾ ＢＧｾ - 40

SNOW LOAD OBSERVATIONS ON ROOFS

SNOWFALL /December - MarchI Normal 1963-64 97" 140" FIGURE 17(b) YEAR, 1963/64

LOCATION,P.E.I. NATIONAL

Sheltered Heated Insulated ParapetI'?' N.R.C. lab. h • 47.5' ParapettoGrade ROOF OESCRIPTION h -19.5'

(Exposed, H..led, Insulated,NoParapetl

1.. '

--z<Jr-

NS TechCOlleq' .L _ I

----J

I

ｾＭｾｾ

I

r ..'-___ ... --'... k3 I , r -ｾ --"<, ..,,,"/ -,,... !O 110 "'v10 ' -ｾ｜ ｾ ｲＭＮＮＮＧｾ ,;;;!A

v---..

+-»

, NSTech COII"JO N.R.C. Lab. - - - f - - - -C ' -o 10 10 10

..

ｾ 60 o I N --G> , 1963-64 139"

•.

Engineering Bldg. SNOWFALL (December - March) FIGURE 18 Normal 78"

)

t'l.

/70' < : : < -(Sheltered, NotInsulated, Heatedl

N W+E S OCTOBER ':: 110 -a: ;: 0 z 80 ｾ 0 < co 40

"

'"u u ｾ 0 -", 40 ｾｉ ;00: >- . ｾＢ ; ; 0 10 Xw ｾｾ ＬＬｾ 0 50 ': 31 ｾ 0 ｺｾ ｾＢ Ww ＬＬｾ -40

SNOW LOAD OBSERVATIONS ON ROOFS

YEAR, 1963/64

LOCATION HALl FAX, N.S.

40 10 0-14 r-I r-I ' , . -r-J I T I I ROOf DESCRIPTION 0-14 ｟ＢｚｾＭＭ

ExlXlsed, Heated, Insulated

SNOW LOAD OBSERVATIONS ON ROO FS

160 "'-110 ｾ ｾ C ;0: 0 z ₈₀ ｾ C ｾ ｾ 40

'"

ｾ u u C 0 0 -40 _N ::::i W+E ;0:0: >- . S ｾＧＢ 10 C 0 0 X w ｃｾ ＢＧｾ SNOWfALL lNo",ermer -Marchi Normal 1963-64 138" 168" FIGURE 19 YEAR, 1963/64

LOCATION,GOOSE BAY, LAB.

/ / / / X / I / i

,

ｾ 1 \ I \ -' ' / \/ ＭｊＭＫＭｾＭＭ I ' / /' S- S NOVEMBER

---1---OCT08ER 31 100

.

0 C 3 ₈₀ 60 40 10 >-ｾ Cc o ｺｾ c " , ｾ ｾ ·40

ROOF DESCRIPTION

I. 8UILDING 64

Mech.Equip.Room

IE,posed,Healed, In,ulatedl

IjO'

INat ShelteredExcept fromｅ｡Ｌｾｮｯｬ Healed, In,ul.ted) " , , , -, , ,

---"

'--1-"",

\

ＭＭｾＭｾＭＭＭﾭ

I / -.' f 7 7 7 Building64 ---+----+- --

--+-t--, ! ＭＭｾＭＭＭＫＭＭ

---BO 60 40 20

..

0 "" ｾ 60 40 20

OCTOBER NOVEMBER OECEMBER JANUARY FEBRUARY MARCH APR IL

SNOW LOAD OBSERVATIONS ON ROOFS

120 "" ｾ I ｾ 80 ｉＭＭｾｾｾＭＭｴＭｾｾｾＭ ｾＭ

i

--t-

Ｍｾ

-ｾ

:

1

-o ｾ ｾＭｩｏｾｾｾｾｾＫＭｾｗＭＫｅ I ｾ i ｟ｓＢＭＭＭＭｾＭＢＭＬ +-IJ1----jf---"-1It 1111-"" 20｜ＭＭｾｾｾＭＫ 0 0 ＩＨｾ ;:;; 0 II ｓＧＧＧｏＭＭｴＭＭｾｾＭ

---r--32

J--f--+---j

SNOWFALL (Novermer -April) Normal 1963-64 111" lW' FIGURE 20 YEAR, 1963/64 LOCATION, GANDER. NFLD

ROOf DESCRIPTION 40 fI -20I- ＭＭＭＭＭＭＭＭｾＭ --

ＯＵｾＯＵＯＵ

-/0 10

Ｆ

ｾ Ｍ Ｍ ｌＺＺ Ｇ /5 ----_ -::;....-- r---.-... _.... '" -r ' - - - - ｾ ' " ' -T I • ., 7. /4 I. ".? • /6'-5 ' #0'2(, ' ' ] /0. ＯｾＯｾｾ

/31:, :: :;;

/8.i 1--132'-- ..L-60-..l ME Garage 1--- - I - 1 -42/

r

I j -60 401---t 20 1 1 1 1 -Cantilever Hangar 29 Cantilever Hanger OCTOBER NOVEMBER DECEMBER JANUARY fEBRUARY MARCH APR IL

::3 120 -80 f---+---c

,.

o z ｾ o -c => :E ｾ 40 r---u -c - - -- - - - - + -I ｾＭＭＭ SNOWfALL (November - MarchI Normal 1963- 64 39" 33" FIGURE 21 -40

SNOW LOAD OBSERVATIONS ON ROOFS

YEAR 1963/64

LOCATIONRCAF

.,t

.1.

·1/ .u ./7 .22 so, IS _ＮＲｾ ROOF DESCRIPTION 4'l1'

r---,

303' • I • ｾｬ .19 .74 • J3 , .70 \ 31'

ｾｾｾｾＺＺ

_{ｾｚｚ｟Ｗ} FR.ON-rVICIV Cant. Hangar

--I---+-

_I

I

--1---L t-

'

;

, I ,

1---

₁ - - - -

.---+-I '/---'---+---\ I ---,/ j \ \

··l·:---, ＭＭＭＫ｟Ｎｾ］Ｍ］ＭＫＭ］ｾ］ｆＭｾＺＺＺ］ＮＺＧｪＺＺＺＺＺＺＧ［ＺＢＭＭＫＭＭＭｾ I

-+

_! M.E.Garage o 40 U.S.jepot 101---...+ ----40 o 40 40 10

+

i

I I

r

101- +'

ａｲ｣ｾｈ］｟ＫＭＭＭＮＭ

, 10

OCTOBER NOVEMBER DECEMBER JANUARY FEBRUARY MARCH APRIl

z -c :<: 0 z BO ｾ 0 ｾ ｾ :-; => ₄₀

"

=> u u '" o <::3 --4-0 ｾｉ "'0: ｾＺｩ 20 0 0 ｸｾ ＢＧｾ ＬＬｾ 0 ->0

SNOW LOAD OBSERVATIONS ON ROOFS

U.S.D""t SNOWFAll (Noverrtler - Marchi Normal 1963-64 45" 30" FIGURE 22 YEAR, 1963/64 LOCATION,R.C.A.F.