Housing Trends Prove Effective in Winter

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Housing Trends Prove Effective in Winter

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riod to avoid extra costs ot protecting and heating the concrete. If not, the house sites should be covered with a foot

FIGURE I

L A Y I N G FLOOR ON FORMS A L L O W S H E A T I N G

TO PROTECT GROUND AND CONCRETE

Housing trends prove

effective in winter

By R. E. PLAITS, Housing Section, Division of

Building Research, NRC

Canadian builders now generally agree that year-round building can pay. Housebuilders are showing that the leading production trends for "normal" conditions are also proving most effective in winter.

In less than a decade most project builders have made remarkable advances in construction organization on four fronts:

-In preplanning and sustained marketing;

-In mechanizing wherever it pays; -In moving work into shops (or buying shop components);

-In checking costs and scheduling at all stages.

It is no coincidence that such build, ers are leading in winter housebuilding. They are helpful examples for others, big and small, who work toward the goal of year-round building.

As emphasis on year-round building increases, particularly with the present Government incentive scheme, the les-

sons taught by these builders should be further emphasized.

In the simplest approaches to complete winter house building, excavating and concreting involve close scheduling and protective cover; the entire house shell is closed in quickly with components so that the house becomes its own shelter; and "dry" finishing and prefin- ished materials allow easy completion inside and out before spring.

Reported cost increases range from

$150 to $250 for such houses. If brick veneer is desired, partial shelters and heating are required; if solid masonry construction is required then over-all shelters are necessary in winter. Costs are then reported to be $300 to $400

over similar summer constructions. Such extra costs can be more than offset, however, by savings in overhead and through earlier rent o r sales allowed by winter completions.

Access roads, drainage, water-sewer- power, and lot layout should be completed before severe cold sets in. Where possible the excavation and foundation should also be complzted within this pe-

or more of straw to keep them in a frost-free state until excavating can be- gin. Standard equipment can then be used, with none of the springtime prob- lems of water and muck.

If the frost is more than several inches deep, special rippers can be used. This approach is usually preferred to the older one of burning straw and coal to thaw the ground. The earth a t footing level will be well above freezing immediately after excavating and footings can be formed and placed right away. If this is not feasible, the excavation should immediately be covered with one or two feet of straw. This can be moved back, the footings placed, and the straw again covered over the top to protect the warm concrete. Drain tile and gravel can be put in around the footings in the normal manner, with runs completed to allow for spring run-off. Again, straw must be placed over the tile and gravel to prevent frost heaving.

Most builders use prefab forms for the foundation walls. Insulated types are recommended unless heat is provided to protect the concrete. An ex- cellent approach developed by Prairie builders is b e c o m i n g wellknown throughout Canada and the northern United States:

-The foundation forms are levellcd and the floor joists are placed on then], with subfloor or tempcrary deck applied leaving access directly above the forms for concreting (Figure 1). Tar- paulins can then be placed over the whole floor and around the foundation over the excavated area, or straw can be banked around the entire formwork on the outside. The enclosed space within the basement is heated either by portable salamanders or propane heaters or by installing the house furnace, temporarily hung by straps from the floor joists. This approach protects the concrete foundations in extreme c old weather and warins the ground to allow the placing of the basement floor. The superstructure can proceed before the forms are stripped.

Calcium chloride is often added to the concrete to accelerate the set. About 1% by weight of cement is recommended. Transit-mix concrete is pre- heated in winter for extra protection. Forms should be left on somewhat longer than in summer to allow the concrete to cure properly without ex- cessive drying. Backfilling can then proceed if the fill material is reasonably clear of ice and snow. If not, the excavation should be filled with straw around the foundation to prevent frost heaving. Frost need be no problem if lots of straw is always handy.

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builders can close in the house shell in one day with the simple prefab components that have become part of the project building scene in summer or winter (Figure 2). Sheathed wall panels with windows and doors in place, frame partition sections, roof trusses, gable ends, and plywood roof deck, are quickly assembled so that the house becomes its own complete shelter, and the project is over the hump. Most of the work re- mains to be done, but now it is indoors with the furnace on (often connected the next day to a prefabricated flue).

" ? a - r S Z

FIGURE 2

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Frame components can be erected quickly.

Conventional methods also can be quite feasible for erecting wood-frame shells in winter, for big and small builders. Precut framing is usually assembled on the floor and tilted up into posi- tion. In reasonable weather the shell can be closed in five days. To avoid delays partial shelters can be arranged to keep all material stock piles protected and accessible.

Asphalt shingles are very sensitive to weather and must be carefully handled when cold and brittle, but the roof deck itself can keep snow out and the house dry until the weather is suitable for shingling while work goes on indoors. Staplers simplify cold weather shingling, allowing gloves to be worn. Low slope asphalt shingles are more difficult to apply as the asphalt adhesives are stiff when cold and must be trowelled on. Built-up roofing should be protected by shelter if clone in winter, otherwise damage from entrapped water and from overheated asphalts is very difficult to avoid.

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d L L

FIGURE 3

-

Brick veneer requires heated shelter.

On thc inside, most work proceeds under normal conditions of comfort and control. "Dry" methods are generally simpler and safer in application; dry- wall is applied quickly with normal methods. If plastering is done, it should be kept warm and moist (at least 50

degrees F, preferably 60 degrees F to

65 degrees F) for 24 hours, then kept equally warm but at lower humidities for drying, with windows used for ven- tilation. Direct air currents should not

tion are feasible if carefully planned plied under partial shelters but tempera- and protected. Concrete block founda- tures must be maintained at 50 degrees tions require shelters when built in F or more for two davs.

freezing weather. For brick veneer, _{To avoid shelter and heating costs,} builders generally use polyethylene or _{brick veneer, stucco or exterior painting} other tarpaulins hung from scaffolding _{may be left until spring,}_{without delay-} or from the eaves of the house to form

ing occupancy. c!osed shelters (Fimre 3). These are .

-

heated with salamanders or other heat- Where solid masonry construction is ers, to maintain temperatures over 32 required, the fast close-in attributes of degrees F. Bricks are kept warm and wood frame are not obtainable, and an dry under these shelters, but space lim- over-all enclosure is usually considered itations usually mean that mortar must necessary. Again, considerable heating be mixed outside. must be provided at least at night. play on the plaster surface. It is difficult

to avoid heavy condensation on the windows during this period. This can lead to damage of wood trim and fresh plaster.

"Dry" methods are also the simplest for completing the exterior in winter. Primed or finished sidings can proceed

Sand is first heated over pipes or cul- verts with fires inside, or is ordered for warm delivery just when needed. The mortar is then mixed using heated water, and immediately moved inside the small shelter. The polyethylene film shelter can allow considerable solar heating ef- fect-as much as 45 degrees F above outside air temperature on the sunny exposures-but fuel heaters are needed at least overnight to maintain temperatures above freezing. Stucco can be ap-

Leading winter builders co-operated in the preparation of the movie, "House Building in Winter," produced for the Division of Building Research, NRC, by the National Film Board in 1961. without shelter. These include primed

hardboards, coated aluminums, over- laid plywoods, and wood sidings. Pre- cast concrete steps and walks can be laid. The builder need not wait for spring to finish.

The film is used throughout the country by builders groups. It can be obtained through the National Film Board or the DBR Librarian. The DBR booklet Better Bulletin No. 6 "Winter Construc- tion" discusses most of these points in more detail.

The foregoing outlines the simplest approaches to complete winter house building, but other types of construc-