Construction of an experimental basement fallout shelter

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Construction of an experimental basement fallout shelter

NA TIONAL RESEARCH COUNCIL CANADA

DIVISION OF BUILDING RESEARCH

CONSTR·UCTION OF AN EXPERIMENTAL BASEMENT FALLOUT SHELTER

by

A. D. Kent

Internal Report No. 236 of the

Division of Building Research

OTTAWA September 1961

PREFACE

It was considered worthwhile in the course of erecting a

basement fallout shelter for experimental purposes to use it as an exercise for the checking of the published instructions and plans intended for

householders who may construct such shelters, themselves. The construction procedures followed are now described, with special reference to the deviations and additions found necessary or desirable. The record of the time and materials required is now given and suggestions for improvement of the shelter and of the published instructions are listed. Measurements carried out in the shelter and basement under simulated emergency use will be described in later reports.

The author, a mechanical engineer, and a research officer in the Building Services Section of the Division has a special int erest in the heating and indoor climate in dwellings. The work of constructing and instrumenting the shelter and of keeping the necessary records was carried out by Mr. Paul Chabot, a research technician working with Mr. Kent.

Ottawa

September 1961

N. B. Hutcheon, Assistant Director.

CONSTRUCTION OF AN EXPERIMENTAL

BASEMENT FALLOUT SHELTER

by

A. D. Kent

1. OUT LINE OF THE PROJECT

In early 1960 the Emer gency Measures Or ganization, with the assistance of the Shelter Panel, prepared and published a pamphlet

gi ving detailed suggestions for those wishing to provide, at rno de r at e cost, a basement shelter for the protection of their families against radioactive fallout in the event of nuclear war. The pamphlet, "Your Basement Fallout Shelter - Blueprint for Survival No. I" contained

inforrnation on ventilation, heating, cooking, and lighting based in part on considerations and estimates outlined in Technical Note No. 286 prepared by the Division of Building Research for the Shelter Panel.

As a further step towards the solving of some of the problems of heating and ventilating and to obtain information on the environmental conditions to be expected in an occupied shelter of this kind, the Division of Building Research, under guidance from the Shelter Panel, undertook

the construction of a prototype experimental shelter for study. Arrangements were made with Central Mortgage and Housing Corporation to obtain the

use of a house for a period of a year or more to be occupied by a member of the laboratory staff of the Division. To test the instructions of the pamphlet in practice it was arranged that the occupant should build the shelter himself, using the EMO pamphlet for a guide. The results of this exercise in "home construction" are now recorded. Measurements

subsequently ca.r.r i e d out in the shelter and basement under simulated emergency use will be described in later reports.

2. RESEARCH RESIDENCE

The selection of a house was made by C. M. H. C. bearing in mind the requirements of the Division with regard to proximity of

location to the NRC laboratories, proper basement space, basement headroom, grade level and general suitability of the house for research purposes.

The house selected, subsequently designated as Research Residence No.1. was located at 1351 Avenue R; it was a conventional three bedroom bungalow about three years old and measuring approximately 24 by 34 ft (Figs. 1 to 4). The full-size basement with headroom from 7 ft 3-5/8 in. to approximately 7 ft 6 in. was constructed of concrete block walls with a buttr es s at the

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-centre point of each of the two long walls and two steel posts along the centre line of the basement supporting the steel I -beam. The concrete floor sloped toward a floor drain adjacent to the warm air furnace below

the stairway at the north end of the basement. Grade level was

approxi-mately 2 ft below the floor level and more or less constant around the

basement. Two small windows faced east at the rear and one

double-size window faced south at the end of the hous e r emote from the bas ement

stairway. The hot water tank and laundry tubs were in the northeast

corner which left the southwest corner free from obstructions other than a ceiling-type warm-air heating register and an overhead ･ｬ･｣ｴｾｩ｣ light fixture.

The man selected to occupy the house and build the shelter was a recently married laboratory technician of average physique and

stature with no previous experience in block laying or house construction. He had acquired a good working knowledge of house heating equipment and was experienced in instrumenting a structure for temperature and relative humidity measurement and in compiling and processing records of the indoor climate of houses.

3. PLANNING THE SHELTER

(a) Headroom Measurements

The house was chosen to accommodate a shelter for 5 per sons, with outside dimensions of 8 by 14 ft and with a basement ceiling height of approximately 7 ft 4 in. The first step was to outline the walls of the shelter on the floor with single chalk lines, using Diagram 1 of the

pamphlet as a guide. From this it was obvious that the plan would have

to be revers ed to suit this particular basement location. Floor to ceiling basement heights were then established where each floor joist crossed the chalk line, and at the corner s by means of a 7 ft

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wooden ruler tack-nailed to the upper end. These heights to the under edge

of the joists which varied from 87 5/8 in. to 89 3/8 in. were indicated on a sketch of the basic layout. A long straight edge with carpenter's level was used to check the level of the joists over the long wall; slight adjustments

were made in the measured heights to allow for high and low joists. Contrary

to expectations the point of minimum height (highest floor elevation) was not in the basement corner but along the existing basement wall where the long

wall would begin. At this point the height was 87 5/8 in. From the table

on page 11 of the pamphlet, using the applicable height of 7 ft 3 in., the walls should consist of 8 1/2 courses of 8-in. blocks and a 3-in. "increase in

height to the level wall footing-." It was found later, however, from a study of the dimensions of materials, that a 4 1/8-In, footing could be used. It is respectfully submitted that the planning outlined on pages 10 and 11

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(b) Grade Level Measurement

Although the ground outside the corner of the basement was fairly level, the lowest spot was along the south wall of the house. Measurement from the window sill to grade level outside and from the window sill to the high point of the bas ement floor, which happened to be immediately below the window, indicated a minimum distance of 52 in. from grade level to basement floor.

(c) Materials Measurements

Car eful measur ement of the unit materials was made to ensure proper assembly of shelter components.

(i) Wall block. - Hollow concrete blocks were chosen in preference to solid blocks for the basic structure because of their lighter weight in handling, although when filled with sand the unit mas s of the hollow block is admittedly inferior to that of solid concr ete blocks. The hollow blocks used in the structure measured as follows: full-size blocks

15 3/4 by 7 3/4 by 7 3/4 in., with two core holes each with nominal dimensions of 4 by 4 3/4 i.n , , and half corner blocks 7 5/8 by 7 5/8 by

7 5/8 i n , , with a single core hole measuring nominally 4 by 4 1/4 in. For planning purposes the half corner blocks were assumed to be 7 3/4 by 7 3/4 by 7 3/4 in. with an extra 1/8-in. allowance for mortar joints.

(ii) Roof block. - Solid concrete blocks measuring 15 3/4 by 7 3/4 by 3 578 in. were used for the roof and half course of the wall immediately below the shelter roof joists.

(iii) Roof JOists. - The lumber for the 2- by 6 -i.n, nominal roof joists measured 1 3 4 by 5 3/4 in.

(iv) Roof boards. - Boards for the shelter roof which were nominally 1 by 6 in. measured 5 3/4 in. in width by 3/4 in. thick.

(v) Framing lumber. - Nominal 2 - by 8 -In , lumber for the

timber framing measured 1374 by 7 3/4 in. with nominal 1- by 8-in. shelving measuring 3/4 by 7 3/4 in.

(d) Shelter Floor Plan

In planning the floor layout of the walls using Diagram 1 of the pamphlet as a guide, the following wall lengths were determined:

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-(i) Long wall. - With 10 blocks at 15 3/4 in. plus 1/2 block, and allowing eleven mortar joints at 1/4 in. each, the long wall worked out to 168 in . , or 14 ft as shown in the diagram.

(ii) Short wall (at end bunk). - Five full blocks at 15 3/4 in. plus 2 half blocks and 7 mortar joints at 1/4 in. each carne to a total length of 96 in. or 8 ft as shown in the diagram.

(iii) Wall at side bunk. - Eight blocks at 15 3/4 in. plus 8 mortar joints at 174 in. equalled 128 i.n , , or 10ft 8 in.

(iv) Wall between entrance and shelter. - Four blocks at 15 3/4 in. and 4 mortar joints at 174 in. carne to 64 in., or 5 ft 4 in. This allowed a shelter entrance width of 24 1/4 in.

(v) Outer entrance wall. - Four blocks at 15 3/4 in. plus 1/2 block at 7 374 in. and 4 mortar joints at 1/4 in. each gave a length of 71 3/4 in. or 5 feet 11 3/4 in. Clearance to the basement wall was therefore 24 1/4 in., the same as the doorway to the shelter.

(vi) Inside room sizes. - The wall layout as planned above

resulted in shelter room dimensions (at floor level) of: length - 112 1/4 in. (9 ft 4 1/4 in. ); width - 80 1/4 in. (6 ft 8 1/4 in.). Both thes e dimensions were within 1/4 in. of the nominal dimensions for width and length given in the table on page 7 of the pamphlet. Correspondingly the entrance dimensions were 7 ft 4 1/4 in. by 2 ft 8 1/4 in.

(e) Shelter Elevation

The planning of the shelter elevation was complicated by the fact that a mortar joint of 1/2 in. is called for in both text and Diagram 2 of the pamphlet. Using, for example, the 7 1/4 in. basement headroom of the table on pages 11 and 9, blocks at 7 3/4 in. each plus 9 mortar joints at 1/2 in. would give a distance of 74 1/4 in. from floor to underside of shelter roof joists; adding two blocks as shown in the diagram of the side of the roof would add another 16 1/2 in. for a total of 90 3/4 in. or 7 ft 6 3/4 in., greater than the original headroom. Obviously 1/4 -i.n , mortar joints were intended with blocks of 7 3/4 in. height to give an 8 -In . module.

On this assumption, and working to the headroom of 87 5/8 in., the height of 8 1/2 blocks with 1/4 -in, mortar joints worked out to 67 7/8 in. This meant that a 4 1/8 -in. concrete pad or foundation would allow the

minimum 72 in. or 6 ft of headroom inside the shelter to the underside of the joists. With a joist depth of 5 3/4 in., roofing of 3/4 in. and two layers of solid half blocks at 3 5/8 in. each, the roof added 13 3/4 in. (not 1 ft

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-85 3/4 in., leaving a space of 1 7/8 in. between the top of the roof blocks and the underside of the house joists.

To construct two courses of block wall at the periphery of the roof would have meant 16 in., wher eas with the arrangement planned ther e were only 15 5/8 in. of space. The construction was

altered from the diagram to omit the two top courses of block and extend the roof construction over the top of the walls, using placed concrete instead of the block construction at the top of the wall and ernpl o yln g additional roof boards and half blocks extending to the outer edges of the walls. This meant that all the roof joists could be the same length and allowed to rest on the whole block of each wall instead of only on the

inner edges of the block as shown in Diagrams 3 and 4. The revised design was considered a more stable loading of the walls although protection was

slightly impaired by substituting wood for concrete at the joist ends. The length of the roof joists was therefore increased as were the number of roof boards and blocks from the requirements of the pamphlet.

This revised design worked out well as far as the timber framing was concerned, since the first six courses of-blocks plus the

4 1/8-in. concrete pad equalled the 52-in. ground level minimum, thus requiring 2 1/2 courses of block above the timber framing. It also allowed a level pad of minimum thickness of 4 1/8 in. all around, both below block walls and framing. The diagrams of the pamphlet (with the

exception of Diagram 11) are misleading in this respect since they show the block walls directly supported on the floor with no pad for levelling. It is most important that such a level pad be provided for the blocks as well as the framing. For simple interpretation by the builder the pad should be required to give a uniform level surface all around from which to begin the structur e, and therefor e the brick and concr ete block alternatives shown in the diagrams would only apply if the basement floor were perfectly level.

4. CONSTRUCTION

In the construction of the shelter the pamphlet was followed as closely as possible; any difference in procedure or material from that outlined in the pamphlet is noted and described in detail.

(a) Foundation Pad

The fir st step in the actual construction was to layout the guide lines according to the dimensions arrived at during the planning of

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-the shelter (Fig. 5). The floor surface between guide lines was then gone over with a disc sander to remove as much as possible of the green paint surface to provide a good bond for the concrete. Forms were then

constructed for the concrete pad, using selected I-by 6-in. boards with straight edges on the top and the bottom rip-sawed to the slope of the floor, the contour being obtained from the headroom dimensions taken at each joist crossover. Thus the top edges that were checked for level were to be used to screed the final pad. Strips 1 by 2 in. were nailed along the lower edges for better support and strength (Fig. 6) and across, the top of the form every 2 to 3 ft. This sytem was used in pr efer ence to the suggested method outlined on page 9 and in Diagram 9 of the pamphlet for simplicity in s cr eeding and trowelling; it also r emoved the neces sity of mixing a second batch of concrete for the guide block holes shown in Diagram 2 of the pamphlet. A final check was made with an 8-ft straight edge and carpenter's level to ensure that the top of the form was perfectly level around all the five walls. Concrete was mixed from a commercial concr ete mix and water in a ratio of one 90 -lb bag to 3 qt of water, as called for in the manufactur er' s instructions. This r esulted in a slightly stiff

mix to avoid leakage of fluid concrete at the base of the forms. Concrete blocks were used for 'further bracing of the forms. After placing the mix in the forms the wooden top strip braces were removed one by one to allow the surface to be screeded and trowelled (Fig. 7). The concrete was

periodically moistened at the surface to cure properly; after approximately 60 hours the concrete block bracing ｡ｾ､ wooden forms were removed.

(b) Block Walls

The sequence of operations given on pages 11 to 13 of the pamphlet was reversed, that is, the block walls were first built up at the ends

adjoining the basement walls to the height where the framing should go, and then the framing was built to suit the height of the walls, rather than vice versa. Using a commercial mortar mix and water mixed in the

correct proportiori to provide a thick mortar paste, the first row of blocks was laid up on the concrete pad with 1/4-in. rno rta r joints below and

between the blocks, the level being continuously checked with a straight edge and carpenter's level. The cor e holes of the fir st row of blocks were then filled with sand (Fig. 8) except for the two blocks mortared in on their side to form lower vent holes. As further courses were laid up and filled with sand, a taut string weighted down on corner blocks all' eady laid served as a guide for additional block laying (Fig. 9) and a carpenter's level was used to check the walls for verticality.

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-(c) Timber Framing

When the ends of the sixth course of blocks at the basement walls had been laid up, the framing measurements were taken. Allowing for top and bottom plates, upright 2- by 8-in. members were cut to length on a jig and preassembled with a single top plate. The assembly was then placed in position and the second top plate and bracing added (Fig. 10). Shelving was then a s s ernbl e d in place in a staggered arrangement that required more end nailing and less toe nailing than shown in Dia gr arn s 2 and 3 of the pamphlet (Fig. 11). Anchor blocks were fabricated and fixed to the walls with anchor bolts as detailed in the pamphlet, except that steel angle brackets were used in place of nails to affix the framing members (Fig. 12). A Clear commercial wood preservative was then applied liberally to surfaces of the framing.

(d) Window Blocking

The basement window (Fig. 13), approximately half of which would be within the shelter, r equir ed blocking. It was fortunate that 10 -in. concrete blocks similar to the basement wall were available following the dismantling of the buttress supporting the basement wall at approximately its mid -po int , also after er ecting the end wall of the shelter to the height of the timber framing, the buttress wall could be removed without

seriously impairing the strength of the basement wall construction. The window and frame were therefore removed and the space blocked (Fig. 14), the exterior being finished to match the existing house with expanded

metal lath and sand-cement finish made from commercial mix.

(e) Block Walls i

With the basement window blocked, the erection of the walls was continued. The 2 1/2 courses above the timber framing were keyed into the other shelter walls (Fig. 14) and the hollow blocks in the uppermost course of the long wall were arranged to provide three vent blocks (Figs. 15 and 16). Anchor bolts as illustrated in Diagram 6 of the pamphlet were installed above the framing between the first and second courses of blocks (Fig. 17). At this junctur e the overhead warm air duct, the register and the electric light fixture that would interfere with the shelter roof construction were relocated outside the shelter wall by shortening the duct work and wiring. Also the 4- by 4-in. post and beam framing was

constructed in the entrance to support the roof joists.

(f) Roof

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-to the over -all shelter width and po sitioned on 12 -in. centres. At the end walls two joists were placed above the edges of the wall below creating a form for concrete that was to replace the top course of blocks (Fig. 18). A nominal 1 - by 6-Ln , board along the outside of the long wall to

which the ends of the joists were nailed, and 2 - by 6-Ln, blocking pieces on the interior face of the wall between joists constituted a s irrri.l a.r form for the concrete top of the long wall. A commercial concrete mix identical to the base pad concrete was placed in the forms and screeded level with the top of the joists (Fig. 18). The roof decking consisting of 1- by 6 -In , boards with square edges, was then cut to length and nailed across the joists two or three at a time, so that the laying of the roof blocks could be'

done simultaneously. Two layers of 4-in. solid concrete blocks, (16 by 4 by 8 in. nominal) were placed upon the decking without mortar but with joints staggered (Fig. 18). In laying both the decking and the blocks care was taken to obtain as tight a fit as possible.

(g) Bunks and bther Furnishings

Two double bunks were constructed from poplar plywood and spruce lumber using the suggested design on page 17 of the pamphlet except that 2 - by 2 -in , horizontal pieces were used in stead of 2 by 3 in. as called for. A small table was built with scrap lumber left from the construction of the shelter. A frame suitable for a door or curtain was constructed and fitted tightly into the opening between the entrance and the shelter proper using lag screws and caulking compound. A sheet metal hood was fabricated similar in size to that shown in Diagram 1 of the pamphlet but of the shape illustrated on page 16 of the pamphlet, and was mounted over the central one of the three upper vent blocks.

5. SUMMAR Y OF LABOUR AND MATERIAL COST

All material for the shelter was purchased through the regular purchasing system of the National Research Council. Based on the quoted retail price of materials in the Ottawa district, the following would be the cost of the materials to an Ottawa householder:

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42 bags of co mrne r ci a.l concrete mix at $1.50

MORTAR

13 bags of commer cial mortar mix at $1. 75

SAND FOR CORE HO LE S OF BLOCKS

1 cu yd clean sand

20 bags clean. sand at 60 cents

PARGING FOR WINDOW OPENING

2 bags of commercial sand mix at $1. 75

LUMBER

For shelter proper, including wood preservative For bunks $63.00 $22.75 $ 3.25 12.00 $15.25 $3.50 $81. 00 51.76 $132.76 $379.98 say $380.00

The labour hours for each specific part of the construction were recorded as work progressed. In some cases the exact number of hours was difficult to ascribe to one operation due to a certain amount of operation overlapping. The time involved in planning the construction was particularly difficult to assess because this was the one phase of the construction in which the man executing the construction was not working alone. The assistance in planning which was involved, however, might be expected to be roughly

equivalent to the advice that the homeowner would seek from neighbours and friends who had pr eviousl y constructed a shelter.

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-Labour hours recorded in the planning and construction of the shelter were as shown in the following table.

Working Part Time on Shelter (evenings and weekends)

Total Planning and Construction T'i m e: 248 hour s

At the rate of 4 working hours per day 248 hr

=

At the rate of (4 x 5)

+

=

At the rate of 5 days (35 hour s) per week 248 hr = approx 7 weeks At the rate of 7 days (49 hour s) per week 248 hr = approx 5 weeks

approx 38 hour s 3 hours 7 3 1,3 34 17 38 3 92 15 4 19 20 8 7 30 45 14 7

Construction T'irne : 210 hours

W or king Full TilTIe on Shelter Bunk construction

Door fr arn e hood and table

Planning and ordering rn at e r i al s

TLmber framing

Lag screws for framing

Window r e rno va.l and blocking F'o r rn for foundation

Preparation of b a s ern ent floor Placing foundation concrete

Block wall construction Block wall construction Block wall construction Anchor bolts for block wall

Roof rafter s

Concrete at roof edge Roof deck and blocks

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-CONCLUSION

In the planning and erecting of this basement fallout shelter, using as a guide the EMO pamphlet "Your Basement Fallout Shelter

Blueprint for Survival No.1" the average householder working alone on a "do -it -your self" bases could be expected to spend up to 250 hour s at a cost of approximately $380.00. The time consumed on this trial project represented that required by a technician accustomed to careful work to a good standard, but not specially skilled in the major op e r ati ori s required. The standard achieved was probably higher than that which would satisfy an average person. On the other hand time 'saved by working with less care might well be taken up in tearing down and reconstructing parts of the work (or in introducing compensating modifications) where mistakes are made or inaccuracies creep in. These figures could be varied also with variations in design, erection procedure and materials. For example,

using solid wall blocks in place of hollow blocks filled with sand, the higher cost of the solid blocks and the probable extended time for laying extra weight would have to be balanced against the cost of the sand fill and the time

involved in filling the hollow blocks. The cost of block, sand and other materials will vary according to locality, and considerable additional time can be consumed if it is not possible to store materials immediately

adjacent to the shelter. The use of prepared concrete and mortar mixes probably saved time and effort but resulted in higher material cost.

Certain deviations from the procedure of the pamphlet were made in the interests of simplicity, space saving or soundness of structure,

notably in the construction of the foundation pad and the walls at roof level, the latter deviation resulting in somewhat reduced protection from fallout radiation at the edge of the roof structur e.

On the whole, the erection instructions in the pamphlet were made to be well written and easy to follow. The following suggestions are made for improvement:

1.

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Diagram 2 of the pamphlet.

2. The 1/2 -In , allowance for mortar joint in the text of page 10 and shown in Diagram 2 should read 1/4 in. to correspond with the table at the top of page 11, or, alternati vel yt the instructions should be

revised to refer to a joint plus block dimension of 8 in. , the mortar joint thickness to be deter-mined after measurement of the block selected.

3. The home owner should be advised to draw to scale a sketch of the wall and roof construction, using his me asur ed dimensions of the material (not the nominal ones in the diagram), with the high point of the

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-basement floor as a base elevation and the floor -to -ceiling joist measurement at that point as his basic h e a d r oorri ,

4. Diagram 1 shows four high vents and two low vents. Two high vents and two low vents should be ample for ventilation control if a supplementary curtain opening is used; the elimination of two upper vents would give greater protection from radiation. The upper vent shown at the curtain frame in Diagram 1 should be moved one block to the right.

5. In the shelving design of the timber framing, a staggered shelf arrangement allows end nailing of all shelves to give a rno r e ver satile storage system.

6. The 3-in. rrnrn.rnurn clearance between the top of roof blocks and the underside of house joists appears unnecessarily large. One or 2 in. extra head room in the shelter is very desirable; reduction from 3 in. to 1 in. minimum would not seriously handicap the placing of blocks in the roof construction.

7. There would be greater protection at the basement wall at

grade level if the blocks above the framing began one course below minimum grade level instead of at grade level as shown in Diagrams 3 and 8. The grade level shown in Diagram 2 should be raised.

8. Diagrams 2, 3, 4, 8 and 10 might show the basement floor to advantage on a slope and illustrate the same foundation pad under the block wall as does Diagram 11.

9. The 3-in. layer of brick or concrete block called for in

Diagram 9 applies only to a basement floor, perfectly level in both directions. The foundation procedure followed in the construction of the NRC shelter

is advocated for uneven basement floors.

10. The roof design in the NRC shelter eliminates an eccentric loading of the block walls and reduces the depth required for the roof from 16 in. (two blocks with mortar joints) to 14 in. when the joists, roof decking and roof blocks are extended over the top of the wall. Thus 2 in. of headroom are gained in the shelter with slightly less protection at the roof joists.

11. In Diagram 1 the exhaust hood shows an integrally built pipe, which would be difficult for the average home owner to construct. A hood of the design without a pipe, shown in the sketch on page 16 of the pamphlet would seem to be more practical.

#1"

L... 13 L...

-12. The bunks could be made from two sheets of 4- by 8-in. standard plywood instead of 3 as shown in Diagram 4 of the pamphlet. if the width

were reduced from 2 ft 6 in. to 2 ft. The design as shown requires "patching" of some pieces. The extra 6 in. of space at one side and one end of the

shelter would help considerably to enlarge the crowded quarters.

13. Since the vent openings reduce the protection given by the concrete block walls it is suggested that a shelf be erected along the outer wall below the vent openings and that surplus blocks be piled on this shelf Fo form a

concrete baffle opposite the vent openings at sufficient distance from the openings to avoid impeding ventilation. Blocks for the lower vents could be piled on the floor eliminating the need for a lower shelf.

Figure 1

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Research residence No. I

Research residence No. 1

View looking north

View looking south

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FIGURE 4

BASEMENT

LAYOUT

BR '24G4

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Figure 5 South corner of basement showing shelter guide lines

Figure

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Concrete foundation pad;

forms constructed

Concrete foundation pad; caner et e placed

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Figure 8

Wall construction; first course of blocks

Figure 10

Timber framing; during construction

Figure

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Wall construction; succeeding cour a e s

Figure 11

Timber framing; completed with shelving

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Figure 12

T'Irrxber framing; anchor blocks

Figure 14

Basement window; after blocking m

Figure 13

Baaerrient window; before removal

Figure 15

Wall construction; showing courses above framing

Figure 16

Wall construction; showing vent holes

Figure 17

Wall construction; showing anchor bolts

Figure 18 Roof construction