Crawl Space Drying >> Will Gravel In A Crawl Space Keep Moisture Down

If the dirt under the porch comes up to the level of the sills or joists of the house, these can be protected from contact with the soil by noncorrosive metal flashing or by building the porch as an independent unit separated from the house at all points by an air space 2 or 3 inches in width and  Will Gravel In A Crawl Space Keep Moisture Down covered at the top. 

A safe and perhaps easier method is to abandon the use of the dangerous dirt fill and pour a reinforced concrete porch slab. Will Gravel In A Crawl Space Keep Moisture Down If this is done, a sufficient opening must be left to allow removal of wood forms and to serve as a permanent access for inspection. Where this is impracticable, sheet-metal forms are suggested. 

Contact of Wood With Concrete or Masonry Embedding wood in concrete near the soil is an invitation to decay. Will Gravel In A Crawl Space Keep Moisture Down This is especially true of stakes left projecting through the concrete. For slab-on-ground construction, impregnate plates, sleepers, and any other wood in contact with the slab with a preservative or use naturally durable wood. 

Either treated or naturally durable wood also is desirable for frames and doors of access openings in foundation walls. Will Gravel In A Crawl Space Keep Moisture Down Protect wood posts resting on concrete floors from floor moisture by placing them on raised concrete bases (fig. 5) or by using treated or naturally durable wood. 

If a wood floor is laid on a concrete slab, there should be a damp proof membrane either under, Will Gravel In A Crawl Space Keep Moisture Down in the upper part of, or on the slab (fig. Even with such protection it is safest if sleepers and plates, and the subfloor if it touches the concrete, are impregnated with a water-borne preservative. 

Linoleum or other vapor-barrier coverings on wood floors increase the chance of trouble where moisture may rise through the slab from the ground beneath. Will Gravel In A Crawl Space Keep Moisture Down Vapor barriers are beneficial if placed where they will keep moisture from getting into the wood, but can be harmful if they keep moisture from getting out. 

Around houses with wood floors and masonry walls the outside soil grade should be kept below the level of the joists unless the wall is thoroughly moisture proofed. Will Gravel In A Crawl Space Keep Moisture Down Joists or girders framed into masonry should have a 1/2-inch air space on each side and at the ends, or the ends should be damp proofed. 

Ventilation Under houses without cemented basements, the soil supplies moisture vapor to the air. Will Gravel In A Crawl Space Keep Moisture Down In winter this may condense on the cold sills and joist ends, just as the moisture of the air condenses on a glass of ice water. This "sweating" (fig. 3), if continued, wets the wood to Roll roofing used to cover the soil under a house. 

Such a cover keeps the soil moisture from vaporizing into the air and then condensing on the sills and joists. Will Gravel In A Crawl Space Keep Moisture Down Where roll roofing is used, the crawl-space ventilators, or most of them, can be safely closed during the winter. the point where decay fungi can attack it. 

To avoid this, and also to make inspections possible, leave a crawl space under the house with at least 18-inch clearance under the joists. There are two ways to prevent condensation. Will Gravel In A Crawl Space Keep Moisture Down One way is to provide cross ventilation for all parts of the crawl space by openings in the foundations or skirting on opposite sides of the buildings, best near the corners. 

For most houses, the formula of 1 square foot for each 25 linear feet of wall is sufficient. Will Gravel In A Crawl Space Keep Moisture Down If the vents have grills in them, count only the area of the actual openings. If the vents have louvers, they should be twice as large, or if both louvers and 16-mesh screen, 3 times as large as the formula calls for. 

Insect screen commonly becomes clogged with paint, dirt, and cobwebs; it is better to use 1/4-inch mesh, which keeps out rodents. Will Gravel In A Crawl Space Keep Moisture Down Keep vents open in winter, with such insulation of pipes and floors as may be needed for protection from cold. It is only on the more moist sites that so much ventilation is needed for occupied houses. 

When houses are not occupied and not heated during the winter, Will Gravel In A Crawl Space Keep Moisture Down condensation may occur on all floor members instead of being limited to those near the outside. The second way to prevent condensation is to place a vaporresistant cover over the ground in the crawl space. 

This stops at its source the moisture vapor that causes the sweating, and makes it possible to use smaller vents or to close most or all of the vents during the cold weather without bringing on decay. Will Gravel In A Crawl Space Keep Moisture Down Smooth-surfaced roll roofing weighing 55 pounds or more per roll of 108 square feet has been used successfully under many houses.  

Other vapor barrier materials, such as 6-mil polyethylene, may be used in this way, but the brief experience with many of them to date precludes any recommendation concerning their use. Will Gravel In A Crawl Space Keep Moisture Down Soil cover under basementless houses also decreases the likelihood of moisture condensation in winter in attics and possible subsequent decay. 

For recommended ventilation in attics, see the section on roofs. Where the water supply enters the house at a temperature as low as 50°F., there may be enough condensation of moisture on concealed pipes in walls and floors to favor decay. Will Gravel In A Crawl Space Keep Moisture Down In houses with such a supply system, insulate the coldwater pipes before they are enclosed. Ventilation cannot fill the need in such cases. 

How To Safeguard Parts of Houses Exposed To Rain Porches and Steps As previously stated, overhanging roofs and flashing help to pro­ tect woodwork. Will Gravel In A Crawl Space Keep Moisture Down Some decay is to be expected in porch steps, floors, railings, or pillars exposed to rain. 

This, however, can be much delayed. Provide abundant ventilation under porches. Base the lower ends of stair carriages or stringers on bricks, stone, or concrete, well above the ground level. Will Gravel In A Crawl Space Keep Moisture Down Design the construction, wherever possible, to shed rainwater. 

For example: Build railings so that the handrail extends over the top of the posts or balusters and keeps them from taking rainwater through the ends; make porch floors slope toward the outside; Will Gravel In A Crawl Space Keep Moisture Down see that frames for screens have openings through the bottom of the frame to let rainwater escape.

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