Snow loads on roofs 1966-67: eleventh progress report

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Snow loads on roofs 1966-67: eleventh progress report

Kennedy, I.

NATIONAL RESEARCH COUNCIL OF CANADA

DIVISION OF BUILDING RESEARCH

SNOW LOADS ON ROOFS 1966 - 67

ELEVENTH PROGRESS REPORT

by

1. Kennedy and D. A. Lutes

.

,

ｾ

Internal Report No. 364

of the

Division of Building Research

OTTAWA

Because of the importance of snow load as the major design load on roofs in Canada, continuous efforts are being made to obtain a better basis for the prediction of snow loads on roofs.

This report presents the results of the final year of a 10 -year countrywide survey of Snow Loads on Roofs in the form of graphs, tables and photographs and includes a discussion on future snow load

studies. Observations were made on 40 roofs at 15 A Stations; B-Station

reports were prepared by DBR staff on about 20 large roofs in the Ottawa area and on several others in the mountains of B. C.; and C-Station reports on 23 roofs were received from 8 Canadian Forces Bases.

This general survey has provided the information needed for the revision of snow load requirements in the National Building Code of

Canada. It has been discontinued after the 1966 -67 winter in favour of

two new more specialized studies aimed at filling some gaps in the

information available from the A, Band C Stations of the general survey.

These gaps concern snow loads on large flat roofs and snow loads in the mountains, both of which will be the subject of future reports.

The Division of Building Research wishes to record here its appreciation to all observers across Canada whose excellent work, often done under difficult conditions, made possible this general survey

of Snow Loads on Roofs. In particular, special appreciati.on 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.

1.

National Park; Laval University (Quebec); MacDonald College (St e, Anne de Bellevue); Queen's University (Kingston); University of Alberta (Edmonton); University of Waterloo, Aluminum Company of Canada at

Arvida; Mrs. P, Curtis at Inuvik; and the Atlantic, Prairie and B. C.

Regional Stations of the Division. Thanks are also here recorded to

the Chief of Defence Staff, Air Force Headquarters, Ottawa, and to the

R. C. A. F. personnel at C Stations at Comox. Lancaster Park, Cold

Lake, Winnipeg, North Bay, Ottawa, Goose Bay and Toronto. and to the building inspectors and individuals who made the observations at

B Stations. Without all this willing co -operation this survey could not

have been carried out.

This report was prepared by I. Kennedy of Queen's University,

a summer worker with the Building Structures Section and D. A. Lutes,

Research Officer with the Section, under the direction of W. R. Schriever.

Ottawa

December 1968

( ii)

R. F. Legget Director

Page

SURVEY PROCEDURES OF 1966-67 OBSERVATIONS... 3

A Stations B Stations C Stations 3 3 4 W E A T H E R . . . 4 PRESENTATION OF RESULTS. ... . .. . . .. . . 5

RESULTS OF THE 1966-67 OBSERVATIONS... 5

Average Loads 6 Drift Loads 6 A Stations 7 B Stations 10 C Stations 10 CONC LUSIONS . . . 11 FUTURE STUDIES 12 REFERENCES , . 13

SNOW LOADS ON ROOFS 1966 - 67 ELEVENTH PROGRESS REPORT

by

1. Kennedy and D. A. Lutes

Because of the importance of snow loads on roofs in the cold

climate of Canada, continuous efforts ar e being made to obtain a better

assessment of snow loads on roofs as a basis for an improved formulation

of design snow loads in the National Building Code (l).

In

general term s

the problem is to recommend a design snow load that is high enough to r educe the probability of failur e to an acceptable level but, at the sam e time, not so high that unreasonable construction costs will result.

Early design snow loads were specified in the National Building Code (1953), for differ ent locations across Canada, on a map showing

"contour lines" of equal snow load. These loads, which were used as

design loads for roofs, were based directly on measurements of maximum

ground snow depths observed over a number of years. It was obvious,

however, that in some cases these loads were too high and thus uneconomical,

and that in others, they were too low. Even superficial observations showed

that roof snow depths were often much less than ground snow depths, and

that measurements of ground snow depths were not, therefore, directly

applicable to the determination of roof snow loads.

In

view of these considerations, the Associate Committee on the

National Building Code asked the Division, in 1957, to carry out a

country-wide survey of actual accumulations of snow, ice, and rain on

roofs. The fir st full survey observations were made during the winter

of 1957-58, with more than 50 observers across Canada co-operating in

this work. Ten Progress Reports (2-11) including a pilot survey have

been prepared over the years summarizing the results of this survey. This present report gives the results of the tenth year of observations (1966-67) of the "Survey of Snow Loads on Roofs".

Three types of stations were set up for ch e survey. At A stations

the observers measured snow depth and density of the snow, mainly on flat and pitched roofs of residential size and, for comparison, on the

adjacent ground. At these stations snow depths on the roofs were measured

by means of mounted gauge sticks and on the ground with a yardstick. The

density was determined by taking samples of a known volume of snow and weighing the melt water.

At B stations observations of extreme or unusual snow load

conditions or roof failures were made by volunteer observers. This

infor-mation has been used to build up case records concerning the nature and causes of snow load formation (12).

At C stations observers made the equivalent of A-station observations on very lar ge roofs located at Air Force Bases acros s the country.

A brief review of the developments in dealing with snow loads in

the National Building Code may be useful. In 1960 the survey of snow

loads on roofs had provided sufficient evidence on the relationship between ground and roof loads to enable the Committees responsible for the

revision of the Code to make some changes in the roof loads compared

with the ground load. The roof load was set at 80 per cent of the ground

load, the ground load being based on a return period of 30 years and ad-justed to allow for the increase in the load caused by rain-water absorbed

by the snow. Some nominal allowance was also made for drift loads.

In the 1965 Code further changes were made by the Revision

Committee on Structural Loads and Procedures and this led to a mar e

rational approach to snow loads for the design of roofs.

All roof loads were based on the snow load on the ground and, consequently, the column for the roof snow load in the Table of Design

Data for Selected Locations in Canada in Supplement No. 1 (13) was

omitted. The basic roof load was again set at 80 per cent of the ground

load except that for roofs exposed to the wind a roof load of 60 per cent

of the ground load could be used under certain conditions. This reduction

of roof load for exposed roofs to 60 per cent of the ground load could only be made because, at the same time, allowance was made for a variety

of influences causing accumulations of snow loads on roofs. This was

done by means of "snow load coefficients" or shape factors, which are

shown in the form of diagrams and simple formulae in Figures 2 -1 to

2 -7 of Chapter 2 of Supplement No. 3 (14) to the NBC "Structural

infor-mation for Building Design in Canada". Explanations of the use of these

coefficients are also gi ven.

After ten years of observations of the survey of snow loads on

A-, B- and C-station roofs, the status and direction of the

survey were reviewed. It was agreed that this general survey, carried

out according to certain guidelines described (15, 16) had, on the whole,

served its purpose by supplying the material needed for the revision of

snow load requirements in the NBC, but that it could be discontinued after the

1966 -67 winter in favour of two new more specialized studies. These

studies would be aimed at filling some gaps in the information available

3

-loads on lar ge flat roofs and snow -loads in the mountains. The collection

of observations on typical or unusual accumulations of snow on selected roofs, which allowed the publication of case histories (12) for the use of designers, will, however, be continued.

International co -operation in load studies was illustrated by a paper on the preparation of standards for snow load on roofs published by CIB, co -author ed by a DBR staff member and a Soviet scientist (17). SURVEY PROCEDURES OF 1966-67 OBSERVATIONS

The procedures followed in the DBR snow load survey for the 1966 -67 winter wer e the same as those of former year s.

A Stations

During the winter of 1966-67 a total of 40 roofs were observed at

15 A stations. This total included all of the roofs observed in the previous

year's survey plus a spherical dome surface on the NRC property in Ottawa. At most A stations at least one flat and one gable roof wer e observed.

As in the past, A-station observers measured and recorded in detail the depth and density of snow on the ground and on the roofs.

Observers were asked to take readings once a week and after each heavy

snowfall; although most of them complied with these instructions, some

sent only a few observations. All the A- station results that were received

are included in this report. B Stations

B -station observations differ from those at A stations in that they are single reports of snow loads that are unusual in magnitude or distribution, or that have caused structural failur e of a building.

Observers are encouraged to make data as complete as possible and to

include photographs, or at least rough sketches, showing the depth and

shape of each snow accumulation, with a qualitative indication of the snow

density. Many of the B -station reports were later incorporated in a

collec-tion of snow load case histories being compiled by the Building Structures Section of the Division of Building Research.

For the 1966 -67 winter, DBR staff per sonnel pr epa r e d B -station reports on about 20 large roofs in the Ottawa area and on several others

in the mountains of British Columbia. No B -station reports were received

C Stations

The C -station observations consist of depth and density

measurements of snow on the ground and on the roofs of large buildings

at airports across Canada. All of the airports in the survey are

Cana-dian Forces Bases (CFB), formerly termed RCAF bases. At each

station observations are made once a week and after each heavy

snow-fall on two or more of four standard roofs - the cantilever hangar roof

(flat), the arch hangar roof (curved with flat wings), the mechanical

equipment garage roof (flat, split level), and the unit supply depot roof

(flat). In total, eight Canadian Forces Bases reported on 23 roofs this

year.

WEATHER

The three main climatological factors (snowfall, temperature, and wind), affecting snow loads on roofs are plotted against time along with the snow load for the A and C stations in Figures 3 to 25.

Climatological information for this report was obtained from the

Meteorological Branch of the Department of Transport. Where a city

with an A or C station did not have a weather office itself climate infor-mation from a nearby centre was used; for all stations the location of the corresponding meteorological station is indicated beside the plotted data. Temperature and snowfall data were obtained for all stations, but for

several stations no wind readings were available while for other s only

those gust speeds greater than 18 mph were published. For this reason

several of the graphs in Figures 3 to 25 ar e incomplete.

In general, snowfall for the 1966 -67 winter season was above

normal. The only exceptions were the two stations in the extreme north

and west (Inuvik and Comox) and Ste. Anne de Bellevue, which had

below-normal snowfalls. Two central Canadian stations (North Bay and Winnipeg)

recorded near - normal snowfalls. At all remaining stations the winter

snowfall was from 10 to 50 per cent above normal.

Temperatures across Canada were generally above normal until January, and then considerably below normal in February, March and

April. Exceptions to this were the Prairie region, which was colder

than normal all winter, and Inuvik and Comox which had warmer -than-normal weather nearly all winter.

5

-PRESENTATION OF RESULTS

Detailed results from A stations are presented here, as they have been in previous snow load progress reports, by means of a graph for each roof on which ground load, minimum, maximum, and average roof loads

are plotted against time. The number of the gauge at which the maximum

roof load is located is also noted. For one building the maximum load on

a lower canopy roof is also plotted against time. Included for each station

ar e the climatological graphs descr ibed a Ir eady, on which accumulated

snowfall, daily maximum or peak wind speed (with directions), and daily

mean temperature are plotted against time. Snowfall totals for the winter

months are shown under the sub -headings "Normal" and"

1966 -67."

Also

included are drawings showing the principle dimensions of each building

and the location of snow gauges on the roof. These detailed results, that

comprise Figures 3 to

17.

are summarized in Table

1

and in graphs of

Figures 1 and 2.

Observations from B stations are summarized in Table I I and pictures of two of the roofs are shown in Figures 26 and 27.

Observations from C stations are treated in exactly the same manner as those from A stations; detailed graphs for each roof are shown in Figures 18 to 25, and a summary of results is contained in Table III.

Table IV presents roof/ground load ratios for large flat roofs at both A and C stations.

RESULTS OF THE

1966-67

OBSERVATIONS

This discus sion will deal with the relationships among maximum roof load (drift load), maximum average roof load, maximum ground load,

NBC ground load, and NBC design roof load. These terms are, therefore,

defined her e as follows.

Maximum roof load (sometimes called drift load) - the greatest roof load r ecor ded at any snow gauge during the winter.

Maximum average roof load - the greatest average load over the entire roof recorded during the winter.

Maximum ground load - the greatest average snow load on the ground recorded during the winter.

NBC ground load - the 30 -year ground snow load given for the location in Supplement No.1 to the National Building Code 1965 (13).

NBC design roof load - the design roof load calculated as a fraction

of the 30 - year ground snow load accor ding to paragraphs 4. 1. 3. 7. to

4.1. 3. 10. of the National Building Code 1965 (1). Average Loads

On the average, the maximum average roof loads at A stations were only 21 per cent of the corresponding NBC design roof loads, with the largest (56 per cent)occurring on one of the roofs observed

at Ottawa. The maximum average roof loads were (on the whole) only

34 percent of the corresponding maximum ground loads, with only a Halifax roof (124 per cent) having an apparent maximum average roof load greater than the maximum ground load.

Two C -station roofs, both relatively small flat roofs at the base of a large arch roof, had maximum average roof loads which

exceeded both the corresponding NBC design roof loads and the maximum gr ound loads for the winter becaus e heavy accumulations occurr ed behind the raised door housings at the ends of the hangars.

Drift Loads

Twelve per cent of A -st at ion roofs had drift loads which exceeded the NBC basic design roof load, wher eas for C stations they wer e about

60 per cent. This is to be expected since the C -station roofs ar e lar ger

with drifts occurring on lower level roofs or behind parapets. If, on the

other hand, the drift loads are compared with the maximum ground load, it is found that 28 per cent of the A -station roofs had drift loads gr eater

than the corresponding maximum ground load. Many B -station reports

provided further examples of the drift load exceeding both the ground load and the NBC design roof load.

A more detailed discussion of the observations from individual A

stations follows. Where a meteorological quantity is compared to normal,

the normal is given in parentheses; where a snow load is compared to an NBC value, the latter follows in parentheses.

7

-A Stations

Inuvik, N. W. T. (Figure 3) - Despite the fact that snowfall

from October to April was 10 percent below normal (60 in.), the ground load in March and April reached 73 per cent of the NBC ground load for

Inuvik (46 psf), one of the highest values in this year's survey. Even

with this relatively lar ge ground accumulation, however. and the generally low wind speeds typical of this ar ea. the average roof loads wer e all

small (21 per cent or less of the corresponding NBC design roof load). The maximum drift load on the residence roof equalled the NBC value.

Edmonton (Figure 4) - This city, with snowfall 33 per cent above normal (47.6 in. ) for the winter, had a maximum ground snow load of

12 p sf, the lowest among the A stations. Drift loads on roofs observed

were less than 5 psf on both the flat and gable roof and both had large bare areas at various times during the season.

Saskatoon (Figure 5) - This city experienced a "tough" winter. For the months of November to April Sa skat oon' s mean daily temperatures averaged 5.3 degrees below normal which represents the greatest seasonal

deviation from normal observed in this survey. Furthermore, the total

snowfall was 43 per cent above normal. High winds. however, kept

average roof loads below 20 per cent of the NBC design load values (21 psf)

on all five roofs observed. Drift loads on two of the roofs exceeded the

maximum ground load but not the NBC roof load.

Winnipeg (Figure 6) - The winter here was also about five degrees

colder than usual but total snowfall was about normal. The maximum ground load was one -third the NBC ground load value and the maximum roof loads (drift loads) were only one -quarter the NBC design roof load.

Waterloo (Figure 7) - Snowfall in Waterloo was 41 per cent above normal (53 in. for November to April) but. probably due to frequent thaws. the ground load never exceeded 25 p sf, which is well below the NBC ground

load value of 60 psf. Average roof loads were also small (one -half the

ground load or less). During late January and February the drift load.

which occur s every winter on the Engineering Building roof in the lee of the higher Main Engineering Building, reached a value up to 24 per cent greater than the maximum ground load (19 psf).

Toronto (Figure 8) - In spite of the heavy snowfall for this area, the maximum ground load of 15 psf was only 37 per cent of the NBC ground

load for Toronto (40 psf). Frequent thaws throughout the winter prevented

any larger accumulation of snow. Average roof loads were generally low

(in fact the gable roof was frequently bare) but three heavy snowfalls in

January and February resulted in drift loads of about 1.5 times the maximum

ground load (15 psf) on both roofs. Other factor s contr ibuting to the

forma-tion of these unusual accumulaforma-tions were the 2 ft 2 in. parapets on the flat roof and the high winds that were able to affect the snow distribution even

though both roofs were classified as 'Isheltered".

Kingston (Figure 9) - Snowfall in Kingston was. above normal

(43 in.), but ground loads were not exceptionally large. Winds blowing

in from Lake Ontario deposited snow in concentrated loads in the lee of the 2 ft 6 in. parapets on the flat roof of McNeil House creating drift loads

of more than 2.5 times the ground load. A maximum average roof load

86 per cent of the size of the maximum ground load (15 psf) was observed. This was due to anomalies in the locations of the roof measurements.

Ottawa (Figure 10) - Snowfall in Ottawa was 20 in. above normal for the months of January and February and 8 in. below normal in March.

Total snowfall was 17 per cent above normal (83 in.). Of the seven roofs

observed, the three flat roofs had maximum average roof loads greater than 10 psf while the others (three gable and one spherical dome) all had maximum

average roof loads of less than 10 psi. For the only sheltered roof, this

load was 56 per cent of the NBC design roof load (48 p sf}, the highest such

ratio in the 1966 -67 snow survey for A stations.

An interesting addition to the snow load study this year was the

NRC dome, a metal structure with the only spherical roof in the survey.

It was snow -covered in January with a maximum average roof load of 7 psf and a drift load of 17 psi, but was bare for the rest of the winter.

Ste. Anne de Bellevue (Figure 11) Although total snowfall here

was 27 per cent below normal (99 in. ) and maximum average roof load

on the poultry building was less than 8 psi, drift loads on the gable roof

of the East Wing were equal to or greater than the ground load for most

of the winter. The largest roof drifts occurred consistently in the lee

of the main roof which is some 15 ft higher and exposed to predominantly

westerly winds. The West Wing with a low slope shed roof accumulated

9

-Quebec (Figure 12) - Only three reports were received from

Quebec for the 1966-67 winter, but it is interesting to note that the

large, sheltered, flat roof of the Pavillon Vachon had the highest reported

drift load among the A -station roofs. It was 86 p sf, which was 1. 5 times

the ground load at the time, and considerably more than the NBC design

roof load (67 psf).

Arvida (Figure 13) - Total snowfall at Arvida was 20 per cent

greater than normaL but still the maximum average and drift loads on

the roof reached only 17 per cent and 33 per cent respectively, of the

NBC design roof load (45 psf), This was partly due, no doubt, to wind

action pr eventing lar ge accumulations on the exposed flat roof. although

wind speeds at Arvida were relatively low compared to those observed elsewhere in Canada.

P. E. 1. National Park (Figure 14) - Normal snowfall totals for

P. E. 1. National Park were not available from the Department of Transport,

but it appear s from the survey results that the 1966 -67 winter snowfall was

probably greater than normal. The snow load observations indicate that

within this area there are large variations in both snowfall and loading

conditions. For example, the maximum ground load at Stanhope was 66 psf

(the only station in the survey where it equalled the NBC ground load),

whereas at Dalvay it was only 31 p s f, yet the maximum average roof loads

were only 6 p s f and 21 psf on the flat roofs at Stanhope and Dalvay. On the Dalvay roof, drift loads in the lee of a higher part of the same Building were

consistently more than twice the load on the ground. On the other hand,

the exposed gable roof remained virtually bare all winter.

Halifax (Figure 15) - This station's total snowfall was 48 per cent above normal for the winter; it was close to 90 per cent above normal for

the January to March period. The maximum average observed roof load

(16 psf) was less than one-half the NBC design load (36 p sf}. The exposed

flat NRC roof tended to have drifting conditions near its roof projections

but loads were generally small. Frequent thaws prevented large snow

accumulations on Halifax roofs.

Goose Bay (Figure 16) - Snow loading on the gable roof at Goose

Bay produced no unusual effects this winter. Considerable drifting occurred

near the eaves on the east (leeward) side of the roof. but the largest drift load was less than one -half the maximum ground load (45 psf), which in turn was less than one -half the NBC ground load for this ar ea (103 psf).

Gander (Figure 17) - More than 150 in. of snow (29 per cent above normal (118 in. )), fell at Gander during the winter, but high winds kept the roof snow loads small; the maximum average roof load observed

here was 2 psf. Snow drifts of 10 to 20 psf formed on the exposed gable

roof after several heavy snowfalls but they remained for only a few days. Although the "drift load" on the lar ge flat roof never exceeded 1 p sf, an adjacent low canopy roof accumulated drifts of depths up to 64 in. with a maximum load of 172 psf (four times the maximum ground load). B Stations

Among the more heavily loaded B -station roofs were two in Ottawa where drifts seven and eight feet high on low sheltered roofs

caused loads equal to twice the NBC ground load. In British Columbia

four buildings had average roof loads gr eater than their NBC design roof

loads. The gable -roof kitchen shelter at the Illecillewaet Camp in

Glacier Park was especially interesting as it was observed to have an average roof load of 187 psf with drift loading to about 200 psf; snow creep had produced massive overhangs which extended more than six feet from the bu ilding on all four side s.

C Stations

As in the past, average snow loads on the large flat C -station

roofs were relatively small this winter. Wind action produced dr ifting

on many of the roofs. This lead to heavy accumulations in a number of

locations: beside the raised door housing and on the canopies of the cantilever hangars; on the flat wings of the arch hangars; beside the raised portions of the mechanical equipment garages; and on the low

canopies of the unit supply depots. Because all of the buildings are

exposed to the wind the large central areas of most roofs were bare nearly all winter.

One fact concerning the arch hangar roofs must be pointed

out. Although they have been included again this year among the

"large flat roofs" of Table III, they are not really typical of this group.

The arch hangars each have a very large arch roof, spanning 160 ft ,

that is flanked by two relatively narrow (20 ft wide by 160 ft long) flat-roofed wings at the foot of the slopes; the snow gauges for the DBR/NRC

survey are located on these two flat roof sections. Although the total

area of flat roof being observed is about ten thousand square feet, these roofs consist of narrow strips, sheltered by the arch roof whose

11

-geometry the flat roofs accumulate snow which has either slid down from the arch or has been blown over from the windward side and deposited in the

lee of the arch. It is, therefore, not entirely reasonable to consider the

arch hangar in the same category as the other roofs of Table III, most of which are fully exposed to the wind and that consequently are generally fairly clear of snow.

CONCLUSIONS

On the whole the 1966 -67 observations substantiate the conclusions

presented in previous reports. The main conclusions are as follows:

(1) Average snow loads on the majority of roofs are considerably

less than the load on the surrounding ground.

(2) The amount by which the average snow load on the roof differs

from the snow load on the ground (roof to ground ratio) depends primarily

on the degr ee to which the roof is shelter ed. The effects of shelter ar e,

however, difficult to predict exactly.

(3) Whereas well sheltered roofs have ratios up to

nearly all exposed roofs have ratios of less than 0.6. unobstructed roofs exhibit very low ratios.

approximately 0.9, Well exposed

(4) Heavy drift loads, that frequently exceed ch e load on the ground by

alar ge factor, are found in roof areas of localized shelter. Their magnitude

depends on, among other things, the shape of the building, the snowfalL the

size of the "tributary" roof area, and the height of the localized shelter. The

first step in providing designers with "shape factors" to consider in estimating probable accumulations of snow due to drifting and other influences was taken by publishing recommended "Coefficients for Snow Loads on Roofs" in

Supplement No. 3 to the National Building Code, 1965. These coefficients,

however, can only deal with the more common types and shapes of roofs. Since many unusual types of roofs and conditions must be considered, a collection of case histories of interesting snow loads has been published by the Division of Building Research (12) to provide further guidance to the

designer, whose responsibility it is to make the best possible estimate

of the probable snow load. This publication will be revised and expanded

FUTURE STUDIES

It seems appropriate to add some remarks here about future

studies. Ten years of measurements have now been completed in the

general survey of "Snow Loads on Roofs" which has provided a basis mainly for the revisions of the snow load requirements in the National

Building Code of Canada. There is a need for further records in some

specialized areas, particularly in relation to the problems of snow loads on large flat roofs in cities, and snow loads on all types of roofs in the

mountains. F stations and M stations have been set up, therefore, to

make these observations.

The purpose of the F -station survey is to provide information on high and low loads occurring on single -level and multi -level flat roofs because they constitute the most common type of roof on newer commercial

and industrial buildings. One factor to be investigated is the influence of

the size of the upper roof on the drift load on the lower roof for two -level

buildings. F -station observations were started in about a dozen locations

across Canada aft e r significant snowfalls at the time when snow depth is

near the maximum for the winter. It is hoped that ultimately the r ecor ds

obtained will produce such definite information that recommendations can

be made that will improve, even further, the economy and safety of roof

structures in Canada.

The reason for establishing the M stations is that some mountainous areas in Western Canada, particularly at higher elevations, are subject to very high snowfalls resulting in ground loads of 200 psf or more and this

creates a special problem. Weather observations used in preparing Chart

7, "Maximum Snow Load on the Ground", of Supplement No. 1 to the NBC

were, of necessity, made mainly in inhabited locations, hence the chart

applies only to permanently populated areas. Consequently, the lines of

Chart 7 apply generally only to the populated valleys and not to the higher

mountain slopes, where, in some cases, much greater snow depths are

known to accumulate; these must be taken into account in the design of roofs. During the 1966 -67 winter a pilot M -station survey was carried out by two members of DBR staff at Rogers Pass in the Selkirk Mountains of

British Columbia. Measurements of snow depths and densities at various

altitudes were taken at several locations. It is hoped that ultimately the

records obtained will make it possible to establish relationship s between snow load and altitude for mountainous ar ea s .

13 -REFERENCES

1. National Building Code of Canada, 1965.

Council, Associate Committee on the Code, Ottawa, NRC 8305.

National Research National Building

2. Allen, D. E. - Snow loads on roofs, 1956 -57. A Progress Report,

National Research Council, Division of Building Research, DBR Internal Report No. 134, Ottawa, January 1958.

3. Allen, D. E. and C. J. Turkstra - Snow loads on roofs, 1957 -58.

Second Progress Report, National Research Council,

Division of Building Research, DBR Internal Report No. 163,

Ottawa, November 1958.

4. 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.

5. Watt, W. E. and H. J. Thorburn - Snow loads on roofs, 1959-60.

Fourth Progress Report, National Research Council, Division

of Building Research, DBR Internal Report No. 204, Ottawa,

November 1960.

6. 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.

7. Hebert, P. A. and B. G. W. Peter Snow loads on roofs, 1961-62.

Sixth Progress Report, National Research Council, Division

of Building Research, DBR Internal Report No. 260, Ottawa, January 1963.

8. 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.

9.

Pernica, G. and B. G. W. Peter - Snow loads on roofs,

Eight Progress Report, National Research Council,

of Building Research, DBR Internal Report No. 324

November 1966.

1963-64. Division Ottawa,

10. Faucher, Y. - Snow loads on roofs, 1964-65. Ninth Progress

Report, National Research Council, Division of Building

Research, DBR Internal Report No. 339, Ottawa, June 1967.

11. Ho, M. and D. A. Lutes - Snow loads on roofs, 1965 -66. Tenth

Progress Report, National Research Council, Division of

Building Research, DBR Internal Report No. 358. Ottawa, April, 1968.

12. Schriever, W. R., Y. Faucher and D. A. Lutes. Snow accumulations

in Canada .Ca s e Histories: 1. National Research Council,

Division of Building Research, Technical Paper No. 237,

Ottawa,January 1967, NRC 9287.

13. Climatic Information for Building Design In Canada. Supplement

No. 1 to the National Building Code, 1965. National Research

Council, Associate Committee on the National Building Code,

Ottawa, NRC 8329.

14. 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.

15. Allen, D. E. - Snow loads on roofs. The present requirements and

a proposal for a survey of snow loads on roofs. National Research

Council, Division of Building Research, DBR Internal Report

No. 106, Ottawa September 1956.

16. Allen, D. E. - Field instructions for observers at "A" stations of

snow loads on roofs. National Research Council, Division of

Building Research, Technical Note No. 233, Ottawa, October 1957.

17. Schriever, W. R. and Otstavnov, V. A. - Preparation of standards

for snow loads on roofs in various countries, with particular

reference to U. S. S. R. and Canada. C.!. B. Paper No.9,

TABLE I

SNOW LOADS FOR A STATIONS 1966 - 67

1965NBC Max

Load Max Max. Avg. Observed

{paf] Ground Roof Roof

Station Roof 60'1. 80'1. (psf) (pst) (psf)

Inuvik, N. W.T. Flat: Heated. insulated. exposed 28 37 33 3 6

Gable: Not heated. sheltered from south 28 37 33 3 6

Gable: Heated, insulated, exposed 28 37 33 6 29

Edmonton. Alta. Gable: Not heated. shelter ed 16 12 12 4 5

Flat: Heated, insulated. exposed 16 12 12 2 3

Saskatoon. Sask. Flat: Heated. insulated, exposed 21 28 10 4 12

Flat: Heated. insulated, exposed 21 28 9 2 12

Gable: Heated, insulated. exposed 21 28 20 3 6

Gable: Heated, insulated, exposed 21 28 12 3 4

Flat: Heated. insulated exposed 21 28 12 I 2

Winnipeg, Man. Flat: Heated. insulated, exposed. 811_{parapet 21 36 15 8 9}

Gable: Heated. insulated shelter ed 27 36 15 2 10

Waterloo, Ont. Flat: Heated. insulated, exposed 36 48 25 13 16

Flat: Heated. insulated, exposed 36 48 19 10 23

Gable: Heated. insulated, exposed 36 48 17 5 6

Toronto, Ont. Gable: Heated. insulated. sheltered 23 30 15 8 23

Flat: Heated. insulated, sheltered, zt"parapet 24 32 15 13 21

Kingston. Ont. Gable: Heated. insulated. sheltered 30 40 18 11 16

Flat: Heated. insulated, exposed, 216"_{parapet 30 40 15 13 39}

Ottawa. Ont. Flat: Heated, insulated. exposed 36 48 38 15 20

Flat' Heated. insulated, sheltered 36 48 43 27 51

Flat: Heated, insulated. exposed 36 48 29 10 24

Gable: Heated, insulated. exposed 36 48 34 7 14

Gable: Heated, insulated, exposed 36 48 36 8 12

Gable: Heated, insulated. exposed 36 48 31 9 19

Spherical dome: 36 48 29 7 17

Ste . Anne de Gable: Heated. insulated. exposed 30 40 37 8 43

Bellevue. Que. Shed: Heated. insulated. exposed 33 44 37 4 13

Arvida. P.O. Flat: Heated. insulated. exposed 45 60 41 8 15

P.E. I. National Flat: Not heated, insulated. sheltered 40 53 66 6 13

Park Flat: Not heated. insulated, sheltered 40 53 31 21 66

Gable: Heated insulated. exposed 40 53 27 I I

Halifax. N.S. Flat: Heated. insulated, sheltered 27 36 14 8 17

Gable: Heated. not insulated. sheltered 27 36 31 7 8

Flat: Heated. insulated. exposed 27 36 13 16 19

Goose Bay. Lab. Gable: Heated. insulated. exposed 62 82 45 11 21

Gander. Nfld. Flat: Not heated, insulated, exposed 37 50 42 I I '

Gable: Heated, insulated. exposed 37 50 26 2 19

SNOW LOADS AT B STATIONS 19l!6 - 67

NBC Roof

(p sf) Loads intlsf

Type of Heated and 1965 1965 Avg. Roof

Location Roof Insulated 800/0 60% Ground Roof Drifts Remarks

Rogers Pass, B. C. . Flat Canopy No 129 97 52 52 61 Strong winds. Canopy sheltered by

higher roofs

. Glacier National Park, B. C. Gable No 128 64 70 Alum inurn roof

"

"

"

Small slope No 130 123 135 Sheltered

"

"

"

Steep No 117 88 109 Sheltered

"

"

"

Steep No 117 95 . 107 Sheltered

"

_"

_"

Gable No 125 110 127 Sheltered

"

"

"

Low Slope No

-

187 200 Sheltered

Glacier. B. C. Gable No 129 97 200 120 125 Uniform roof load

Mica Creek Village, B. C. Flat Yes 147 86

-

Exposed

"

"

"

Flat Yes 140 114 140 Exposed

"

"

"

Flat No 165 123 .

-

Exposed

"

"

"

Flat Yes 200 127 130 Snow removed early in winter

"

"

_"

Flat Yes 178 144

-

Exposed

"

_"

_"

Low Slope Yes 160 124

-

Exposed

"

"

"

Low Slope No 150 146

-

Exposed round water tank

"

"

_"

Flat Yes 180 125 136 Exhaust fan on roof

Ottawa, Ontario Flat No 48 36 27

-

111 Multi-level roof. Drift on lower leveL

"

"

Flat Yes 48 36 25 13 62 Drift on canopy

TABLE III

SNOW LOADS FOR C STATIONS 1966 - 67

(All loads in 1b./sq. ft.)

Roof Supply Depot Arch Hangar M. E. Garage Cant. Hangar

1965 NBC

Roof Load Max. Max. Max. Max. Max. Max. Max. Max. Max. Max. Max. Max.

Station 80% 60% Ground Avg. Roof Drift Ground Avg. Roof Drift Ground Avg. Roof Drift Ground Avg. Roof Drift

Cornox, B.C. 46 34

-

0 0 6 0 0 6 2 3 6 1 3

Edmonton, Alta. 22 16

-

-

-

-

-

- 21 7 21 20 14 30

Cold Lake, Alta. 33 25 30 12 27 26 31 95

-

-

- 27 14 61

Winnipeg, Man. 36 27

-

0 0 (Insufficient datal

-

0 0 (Insufficient data)

North Bay, Ont. 43 32 26 15 32 38 60 132 34 14 85

-

-

-Toronto. Ont. 32 24 8 4 16

-

-

-

12 6 30

-

-

-Ottawa, Ont. 48 36

-

-

-

48 18 57 47 10 53 50 15 57

-1966 - 67 SNOW LOADS ON LARGE FLAT ROOFS

Max. Avg. Max. Ground Roof Load x 100

Roof Load Load Ground Load

Location Roof (psf) (psf)

(%)

Inuvik, N.W.T. Post Office 2.8 33. 4 8

Comox, B.C. Arch Hangar 0 5.9 0

M.E. Garage 1.8 5.9 31

Cant. Hangar 1.4 5.9 24

Edmonton. Alta. M.E. Garage 6.9 20.8 33

Cant. Hangar 13.7 20. 1 68

Cold Lake. Alta. U.S. Depot 11. 7 29. 5 40

Arch Hangar 31. 1 26. 3 118

Cant. Hangar 14.4 26.8 54

Saskatoon. Sask. Gymnasium 4. 3 10. 1 43

Winnipeg. Man. Library 7.8 14.7 53

U.S. Depot

}

Arch Hangar Insufficient data

M.E. Garage Cant. Hangar

Waterloo. Ont, Main Engineering Bldg. 12.6 24.8 51

Engineering Bldg. 9.8 18.9 52

North Bay, Ont. U.S. Depot 15.2 26.3 58

Arch Hangar 59.8 38.0 157

M.E. Garage 13.6 33.9 40

Ottawa. Ont. Arch Hangar 18.3 48.0 38

M.E. Garage 9.8 46.9 21

Cant. Hangar 15.1 49. 5 31

Toronto, Ont. U.S. Depot 3.7 7.5 49

M.E. Garage 5.5 11. 6 47

Quebec, P.Q. Gymnasium 1.3 55.5 2

Pavillon Vachon 24.6 55.5 44

Ar vi da, P.Q. Rolling Mill 7.8 41. 4 19

Goose Bay. Lab. U.S. Depot 25.8 57.7 45

NO. C STATIONS 15 COMOX 16 EDMONTON 17 COLD LA KE 18 WINNIPEG 19 NORTH BAY 20 TORONTO 21 OTTAWA 22 GOOSE BAY NO. A STATIONS 1 INUVIK 2 EDMONTON 3 SA SKATOON 4 WINNIPEG 5 WATERLOO 6 TORONTO 7 KINGSTON 8 OTTAWA 9 STE. ANNE DE BELLEVUE 10 ARVIDA 11 P. E. I. NATIONAL PARK 12 HAll FAX 13 GOOSE BAY 14 GAN DER ...

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ROOF DESCRIPTION

8 0 1 + 1 + 1 + +

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...

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..

ADMINISTRATION BLDG.

s

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314 LAKEｃｒｅｓｃｅｾｔ

ALL MINIMA ARE ZUO \

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ROOF DESCRIPTION

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ｾ

A

ｾｍ ｾａＮａｾｉ

ｾｲ

ＬＺｊ｜ｾａ

I

SNOWFALL ow .10' ｾ S; 20 (NOVEMBER -APRILI

'" ｾｹ V VV _V V'

'\J

'II

V'Yf

T

TTl

VVV

V", ,

V

NORMAL 1966-67

47A' 46"9" 0 50

ｾ

32

ｾ

; s:

ｾＭｴａＭｾｊ

- - - -

r;

-r"

-ｾ A A

t'

FIGURE c, ₀ 6 ｾ 'V

w

'V

VV'

_"VVf7J

...

-40

SNOW LOAD OBSERVATIONS ON ROOFS Year: 1966-67

80 ROOF DESCRIPTION 60f - - - ' - - - + - - - / - - - + - - - - + - - - / - - - 1 254 SUNVIEW 40I - - - , - - - - + - - - + - - - \ - - - - + - - - / - - - j 254 Sunview 20f - - - + - - - - f - - - + - - - - j - - - + - - - j - - - j f--'---'! 80 ..

_-_

...' -...

ｾｾＺＭＭＧＭＭＺｾｾ

-t s

(Healed, Insulated,Exposed)

60f - - - ' - - - + - - - / - - - + - - - + - - - / - - - j MAIN ENG.8LDG. MainEng.Pldg. 40ｦＭＭＭＭｾＭＭＭＭＮＭＭＮＭ ---+---+---+---+---1 ...._-, , _4 - _ 5

,

20ｉＭＭＭＭＭＫＭＭＭＭＫＭＭＭＭＭＫＭＭＭＭＭＭＭＭｦｾｾＢＢＧ［ｾＧ / ' , I , ' - - _ " ｾ s.s , __ ｾＢＭＲＧ AJ2 b:Q 5 ,.A o 80 ,·U

60f - - - ' - - - + - - - j - - - + - - - - + - - - + - - - j IHeated, Insulated,Exposed)

ENGINEERING 8LDG ＯＳＯｾ 0" : El-e FIGURE 7

t - j

SNOWFALL (NOVEMBER-APRIL) NORMAL 1966- 67 53·1" 74·6" (Heated,Insulated, ShelteredI

ALL METEOROLOGICAL READINGS TAKEN AT DEPARTMENT OF TRANSPORT METEOROLOGICAL STATION AT KITCHENER,ONT.

M

MAY APRIL

MARCH

WIN DATA UNAVAILA8LE

NOVEMBER DECEMBER JANUARY FEBRUARY

t

ＬｾｬｴＺ､［ＭｊｾＧｔ

ｾ ｾ｜Ｌ

'

4 O f - - - - , - - - + - - - + - - - - t - - - - + - - - + - - - j V> W :J:: U ｾ .: 120 ..J Ii' ia 0 z V> ₈₀ 0 w !a ..J :::> 2 ₄₀ :::> u u « 0 60 0 ｾＺｩ 40 ia'" ｾ ::I. Cia ｾｾ xc.. ₂₀ «V> ::E 0 50 ｾ ... 32 ｾ 0 zc.. ₀ «::E WW ::EI--40 1 - - - - 1 - - - - + - - - + - - - - + - - - - + - - - + - - - - + - - - 1

-z-.-SNOW LOAD OBSERVATIONS ON ROOFS Year: 1966-67

II DOUGLAS CRES I -.5G· tl'7 • ...J 33 i 1.1 -: _Li·1 ? 11 Douglas cres 37 21 DQuSI"Cres . . . ｾ /? \

'1)

jol

5'11

LJj

b,

ｾｾ ｾＺ

IjM'

Sheltered 37 - G : Bldg. Healed Attic Unheated Ceiling lnsulateo + --: I 7 I

ｾ

I : 21 OOUGlAS CRES I - - - ' - - - + - - -

L

1-

ＭＭＭｬＭｾＭＭ

I I I j so 60 40 20 0 100 SO t;: :t-60 0 « '3 40 20 0

(Sheltered, Heated, Insulated}

I

I

I Ii

NOVEMBER DECEMBER JANUARY FEBRUARY MARCH APRIL MAY

FIGURE 8

SNOWFALL

(NOVEMSER -APRILI

NORMAL 1966-67

54·S" 67-7"

WIND READINGS TAKEN AT ISLAND AIRPORT; OTHER METEORlOGICAl READINGS TAKEN AT 315 SlDOR ST. WEST,TORONTO. I I I I I I I I I I I I ! , I I I I

r1

v---'

I I j I I I i i I </> .., :I: U ｾ 120 -' -' ::t ｾ 0 Bi SO 0 ..,

:3

::> :0; ₄₀ B u « 0 60 o ｾ ｾ 40ＱＭＷＭＭＭＭＫＭＭＭＭＭＭＫＭＭＬＬＭＧＧＭＭｾＭ｟｟ｉ｟Ｍ｟｟ＫＭＭＭ｟Ｋ｟ＭＭｾ｟Ｋ｟ＭＭ｟｟｟｟｟｟ｪ ｾ ｾﾭ <;0 0..,

_..,

ｾ l})20ＱＫＫｾＭＭＭｉｲＭＭ｟｟ｉｗ｟Ｋｊ｟ｦＱ｟ｾｦ｟ＧＫｪｴｍＭｉｈＭ｟｟ｬＱｊ｟｟ｊＴＮ＼ｉｴ｟ＢＧｬ｣｟ｈＫ｟Ｋｬ｟｟ｖ｟Ｇ｟｟Ｍｾｪ｟ＮＮ｟ｬＫｴ｜ｊ｟｟｜｟｟ａ｟｟ｬ｟Ｏ｟ｾ｟ＮＮＮｉＫ｟ｊ｟ｬ｟｟｟Ｋ｟ＭＭ｟｟｟｟｟｟ｪ :0;

SNOW LOAD OBSERVATIONS ON ROOFS Year: 1966-67

100

ROOf DESCRIPTION

60

60

26 EDGE HILL 26 Edgehill

40 ' - - - /4 7[/" I 40' I I 20

ＶｾＧ

ｾ［ＳＺＺｾＬ

- r ; . ' 7· ｾｉ ｾ Ｍｾ

ｾ｢［［Ｌ

-..:: -, B- 1.. 0

-100 ----_.- _{Sheltered I}

Attic not Heated

+-6ldg. Heated

ｾ

80 Insulated .... "-It' 601--- --'" McNeill House <[ McNEILL HOUSE :3 i

r

.1 .4"---_7· 40

vv-

r\

3r. .2 . j ,5. I

1

/-1-40,

ｾＬ

7 7 20 .J • r.

,

.

I

....

ｾａ

ｾＬＬＷ

I ＮＸＷＢｾ I

..

ｾ ..., _N 0 ! ｾ Exposed Insulated I

Attic not Ventilated Attic not Heated 61dg. Heated Parapet Z6"

I

NOVEMBER DECEMBER JANUARY FEBRUARY MARCH APRil MAY '" w :c u I ;l; -' 120 -' rt ｾ 0 z '" 60 '" w li _rr: -' :::>

,..-.---'"

40 :::>

ｾ

ALL METEOROLOGICAL READINGS TAKEN 8Y

u

ｾ KINGSTON, ONT_, HYDRO

0 60 0 ｾＺｩ 40 ｾ｡Ｎ ｾ ｾｾ

< [ 0 _{WINO DATA UNAVAILABLE} SNOWfALL

OW

i

ｾ 20 (JANUARY- MARCH) NORMAL 1966-67 42·5· 47·5· 0 50 _/1

•

/ ' ｾｵＮ 32 - - - - -1

-\fJY\

_Vlf\fVV\

\f'JVV

ＭＭＭＭｾ -ｾ 0 zQ. _{FIGURE 9} < [ 2 0 Y ww 2 .... -40

SNOW LOAD OBSERVATIONS ON ROOFS Year: 1966-67

,10 .v FairhavenWay .IG 40A 80rker Blvd_ I.7 ,. .111 .07 1.8 z.

I.'

J. el21 . , I.10

1-c=:

ｊｾＧ

,I

(E,posed,Heoled,InsuloledI H· II' (Sheltered, Heated, In,ulaledl

Davidson Cres.

ｾ

ｉｉ

12-

J

ｾｾＺＺＺ･､

AirSpace • 7 . . , Ceiling In,ulate<ll4" B ｾ 10 5+' Heatedｂｬ､ｧｾ •G 5. Flat, 10'toEave, .1 .23 4 I 7/" '1

-+-z-ｾＮ

<, MAY

+

ｾＯＮＱＳ

Ij' 13' I APRIL MARCH I i FEBRUARY JANUARY --,---...--_...- 9 89 I- ----DECEMBER NOVEMBER 60 OAVIOSON CRES. 40 20 0 _----. 80 60 FAIRHAVEN WAY 40 I >-ｾ 20 f---

.----l-*'

'" _I "" '3 _{r "} 1_{11 14} 0 80 I 60 I

40A BARKER BLVO 40 I 20 : 0 Ｙｾ o 60 I ! i I

-ALL METEOROLOGICAL REAOINGS TAKEN AT OTTAWA INTERNATIONAL AIRPORT

SNOWFALL (NOVEMBER-MARCH)

NORMAL 1966-67

B2·6' 96·3'

FIGURE 10(a)

SNOW LOAD OBSERVATIONS ON ROOFS Year: 1966-67

BO ROOF DESCRIPTION 60 72 BISHOP 40 I I

--ｾ ｾ , , r:

"----

.../ 20 v

ｾ

_{ＬﾫＭｾＱ} /7r-: , ' - -ｾ

ＬＬｾ

ｾＬ

",

0

,'"

'

" BO 72 Bishop Blvd. 12 Nt;: 60

"D

ｾｐＧＭＢＮ

ｾＧ _{40 BARKER}

T.J.B

'" 40 ＱＱＺｾ

:

ｾ

..

'3 _-"... lExposed, Heated, Insulatedn

ｾ r, '\ /---../ , _ _ _ _ _.______ __ｾ________----L.- \ , , 12 ｾ 20 -I / .. __.J ｾ [:/""40 Barker Blvd. • _

ｾｾｾｾ

U

＾ＭＳＰｾ <:----ｾ

_ｾ

r

Ｎｾ

.

0 _ｾ r ' _______ T:1 0 · ' ]24

a

4-BO I I I

...11·1

.

I IExpose<l, Heated, Insulaled 2"1

I I I

-2-.-

ｾｪＲＧＭＭＭｪ 60 I I I ;-L

t::J

T";"

DB_R _{I I} I

T

ｾＧＴＧ 6· I I _{J2' j} 40 I ,

I

1

..

7 :.? I I I «to I ＬｾＭＭｴＭＭＭＭＭＭＮＬ

J....

, (ExlIose<l, Heated, Insulated I

--. . , ., ' , - - I 20

Ｇｾ

ｾ

r.

1 .- ｾ 0 ＭｾＭ i I I I

NOVEMBER DECEMBER JANUARY FEBRUARY MARCH APRIL MAY

V> I I

...

_i I :I: U I ! ｾ I 120 I I ｾ

ALL METEOROLOGICAL READINGS TAKEN AT

ｾ

ｾ

I

i _{r -} OTTAWA INTERNATIONAL AIRPORT.

;a I 0 . / z V> _BO I

ｾ

'"

...

ti ｾ :> ｾ 40 I u

ｾ

ｾ 0 ...r--60 _i N

.+,

I _I I '" 5 ! ｾ ｾ 40 , ｾ ｾｾ IWIOODIRECTI,

1

.1

ｾ

Ｎｾ

,

i!8

It'M.-T

7\

t)r

A- .j'

ａｾｾ

1

SNOWFALL

...

(NOVEMBER - MARCHI ｾ ｾ 20

rru

VIJ

ＱｾＧ｜ｪｖ

ｾｉｊｻｦｗＧ \tv'V"

U

V

V ,

iy-rv--;W

NORMAL 1966-67 B2'6' 96·3' 0 I 50

Ii£\

_{M 11}

ｾＨ

32

v

V'v;Jrv1\7\

- - - 1 1 -u, "VV

ｾａａＬｍ

ｾ 0 FIGURE lO(b) f- I _V V

V

v -40

SNOW LOAD OBSERVATIONS ON ROOFS Year: 1966-67

I----+---+---+-- ---+- - - + - - - 1 - - - 1 801---+---+---+---+---+---1 601---"---'--- --- i\.':.e. DOME N

•

I 401---,---,---+---- -- ---- ----.---+----+---1 t N.R.C OOME 110-1---+---- --- - ---+---+----+----+---1 o

...

g ｦＭＭＭｾＭＭＭＭＭＭＭＭ ---"!'::..".---""'----+----+----+---1---1 --- - - t - - - j

NOVEMBER DECEMBER JANUARY FEBRUARY MARCH APRIL MAY

::f

120

rt ｾ z '" :;: ｾ ｾ 401---+---b.-L---+----+----+---j---I

r

60

ＹｾｬｲＭＭＭＯ

ALL METEOROLOGICAL READINGS TAKEN AT OTTAWA INTERNATIONAL AIRPORT.

ｾ 401----+---+---+----+----+----+---1 :>i ".OOIRECT"

1:

l'

"-ｾ

ｾ ｾ

- 7\

:

ｾｲ［

1

T ./\ --1\

ａａｾ

iI

'" 20lJ

\J\j

ｗｶｊｙ｜ｊｾ

Vl/Il'wl'

IrJlfVU

ｙｾｾＧＭｩｗ SNOWFALL (NOVEMBER -MARCH) NORMAL 1966-67 B2·6" 96-3" o • 50'1/\ M ｾ 32 'vv -FIGURE IO(e) -40

SNOW LOAD OBSERVATIONS ON ROOFS Year: 1966-67

100

ROOF OESCRIPTION

BOｉＭＭＭＭＭＮＭＭｊＭＭＭＭＫＭＭＭＭＫＭＭＭＭＫＭＭＭＭＫＭＭＭＭＫＭＭＭｾ

POULTRY BLDG (WEST WING)

MAXIMA AT I Poultry oJdg. (West Wmgl

6 0 1 - - - , - - - f - - - + - - - [ - - - f - - - + - - - 1

Poultry Bldg. (East Wing}

Sheltered from West by Moin Roof Heated, Insulated

ＬＬＭｾＬＮ J I ' / i •j. 7

1

J>tr

91 r--=-,2}1 :·2 ; '5 8·1 ' L L . . . - J 'I 1 I

t

5EqICu.1 A-A LL:i.3"--..;..'--:.!'",---Z..:J0,-",ｾＬ

ｾＮＭＭＮＲＧＵＰＬＬＭＧ｟ｾ

Sheltered from Eost by Moin Root Heated) Insulated . --: I ＢＢＧｾＭＭ - --.. _ _ _ J " ....

-ｉＺＭｾｾｾＮＮｩ

\ \ \ \ \

\\

\ \ ｾ･ \ 5 ｾ 20 I I

POULTRY BLDG. (EAST WING) ALL MAXIMA ARE ZERO

40 20 0 100 80 N t;: jt,-60 <> '" '3 40 20 0

NOVEMBER OECEMBER JANUARY fEBRUARY MARCH APRIL MAY

'" '":r u ｾ .r 120 ...J ｾ ｾ 0 z 80 '" 0

ｾ

'" Ii ...J r ::>

,.

40 ::> J---f u u I

r

'" 0 60 :

ALL METEOROLOGICAL READINGS TAKEN AT MONTREAL INTERNATIONAL AIRPORT, DORVAL, PO. SNOWFALL (NOVEMBER -APRIL! NORMAL 1966-67 98 ·7" 72·4" I

W+E

S

20 I\N

VIj I'VVIfr

Ｇｊｾｬｦｊ

'vi

I,i!IVV

W

y

rvvV"wU

ｾ ｖｊｾ｜ｉ｜

o A <> ｾ ｾ 40ｲＮｊＧＮＭＭＭＭＭＭＫＭＭＭＭＭｦＭＭＫＭＭＫＭｾＮＬＮ｟｟ＭＫＭＭＭ｟｟ｩＭＭＭＭ｟｟ＫＭＭＭ｟｟｟｟Ｑ ＾Ｍｾ :! -"'0 0 " , .'" >co. "''''

,.

':; ｾＺＮＧＭ zoo "',. "''''

,...--40 -FIGURE II

SNOW LOAD OBSERVATION S ON ROOFS Year:

Location:

1966-67

STE. ANNE DE

PAVILLON VACHON , r Pavilion Vachon

/ 1,57

I

'6

ｾ

ｾＭ /0. . 7 +. • /I. .8 5- 2_ / / / 40f - - - t - - - - + - - - - 4 - - - - + - - - I - - - - + - - - i o o_« '3 100 _I I GYMNASIUM I I I

I Sheltered, Heated, Insulated, Not Ventilated

20ｉＭＭＭＭＫＭＭＭＭＭＭＫＭＭＭＭＭＭＭＭＭＧＭＭＭＭＫＭＭＭＭＭｉＭＮｾＮｾｾＭＭＫＭＭＭＭ｟｟ｬ o ＮｾＬ Vi -I 8 5 i .2 /r.1 -c:;

Elposed , Heated, Insulated

NOVEMBER DECEMBER JANUARY FEBRUARY MARCH APRIL MAY </> <oJ :J: U i!: ::I 120 1t 3: 0 ｾ 80 f---C> <oJ l;; ..J :::> ｾ ₄₀ :::> u ｾ -40 I ＮｾＭＭＭＭＮｴＭＭＭ｟｟ＫＭＭＭ｟Ｋ｟｟｟｟ｲ］］Ｇｩ｟｟ＭＭＭｦＭＭＭＭＭＭｪ I

ALL METEOROLOGICAL READINGS AT QUEBEC AIRPORT, ANCIENNE LORETTE, P.Q.

SNOWFALL (NOVEMBER -APRIL)

NORMAL ＱＹＶＶｾＶＷ

112·4' 1212'

FIGURE 12

SNOW LOAD OBSERVATIONS ON ROOFS Year: 1966-67