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Home , Basement, Foundation (engineering)

exposed and all wiring connections are concealed. The main service entrance of wires and load center in most is in the utility of the nearest the Facts, point of entry of the electric service. Basics Never locate these in a or where they are not readily visible or accessible. Most homes today require a capacity A FOUNDATION SERVES Several of between 100 and 200 amperes. purposes. It supports the weight of When much of the heavy electrical the and other vertical loads such load is some distance from the main as snow. It stabilizes the house against service center, a subcenter is extended horizontal forces such as wind. It is with a second distribution panel in or- a retaining which supports the der to shorten the length of the circuit earth fill around the house. And often conductors. it is a basement or cellar wall which In the choice and planning of main may need to be a barrier to moisture, disconnect and load center equipment, heat loss, or sound transmission. branch circuits of 120 and 240 volts The most common foundation is the must be provided to care for the needs continuous wall which may be built of of installed circuits. At least two 120- stone, tile, block, brick, or con- volt and one 240-volt circuit spaces crete. Recently, treated , metal, should be allowed for future circuits. and other materials have been used. The cabinet of each load center has a table of numbered circuits. Your electrician should list on this table CONTINUOUS WALL FOUNDATION exactly which area or individual ap- phance is served by each circuit. Finally, require your electrician to have his work checked and inspected for safety. An authorized inspector can furnish you with a copy of the Cer- tificate of Approval. Examples of methods used to cal- culate required circuits, feeders, and main entrances may be found in the Continuous are used to support National Electrical Code, a copy of heavy loads or to enclose a which may be purchased from your or basement. If enclosure of space is State fire insurance writing bureau the main objective, then the wall may which is most likely in your State be built of lighter, more porous insulat- capitol, or obtained from the National ing materials which will reduce heat Fire Protection Association, 60 Battery- loss and sound transmission. march Street, Boston, Mass. 02110 for A step foundation is a continuous $3.50. wall of variable height. It is used on Other helpful guides may be ob- steep grades or for with partial tained from the National Electrical . Manufacturers Association, 155 E. 44th The pier foundation is a series of Street, New York, N.Y. 10017, or from piers which support the house. They the Residential Group, Electric Energy are generally masonry but sometimes Association, 90 Park Avenue, New York, N.Y. 10010. AUTHOR JERRY o. NEWMAN is an Agricul- State universities and your power tural , Rural Housing, Agricultural supplier generally have pamphets. Research Service.

164 POLE FOUNDATIONS The beam is especially useful in PLATE K? PLATE iff dry climates or drained scnh where the house can be built close to the ground.

SLABS SLAB FOUNDATION

they are made of other materials. The pole or post foundation is a special kind of pier foundation built of pres- sure-treated wood. It is often used on KJJ FOUNDATION steep where there is considerable variation in the height of the piers and where a regular masonry pier might The slab foundation is a special bend and break. foundation which floats on top of the Beams placed between the piers of and also serves as the of a pier foundation support the house. the house. The slab is thickened under all of the walls to support their heavy loads. All slab are not slab founda- BEAM SIZE DEPENDS tions; many are simply floors. ON PIER SPACING^ ^ A separate foundation supports the wall loads. Every foundation must support the weight of the house and its contents. This load can vary considerably de- pending on the type of , the kind of , and the special uses the house is subjected to. In colder The size of such a beam depends on the load it must carry and the distance climates, the foundation must carry the ice and snow which may accumulate on between piers. The space between piers the . If the foundation loads are is generally enclosed with curtain walls heavy, will provide which carry no load and whose main the strongest wall. Wider masonry purpose is to enclose the space and act as a barrier to wind, heat, moisture, and walls will carry heavier loads than nar- row ones. sometimes, animals.

GRADE BEAM WHAT IS A.. . 1^

FOUND AT rON

CONTINUOUS CONCRETE STONE FILL PIER

A grade beam foundation is a pres- Some houses are so heavy that the sure-treated wood or reinforced con- foundation must be widened at the crete beam which is submerged to a bottom to keep them from sinking into depth of about 8 inches below grade. the soil. The widened bottom on the It may be supported on a stone fill or foundation is called a footing. Its size on underground piers which extend depends on the kind of soil under it. into the ground below the frost line. Soil strengths vary from 1,000 to

165 490-100 O - 73 - 12 12,000 pounds per square foot. In FOUNDATIONS CAN general, footings are designed for BREAK OFF OR OVERTURN 1,000 pounds per square foot, but if you know your soil type you may design smaller footings.

FOOTING THICKNESS tying the wall to anchors in the soil, u or counter-balancing the wall. T THICKNESS 1 PREVENT WALL OVERTURN THICKNESS =11/2 X THE LARGEST PROJECTION

Thickness of the footing depends on how far it protrudes beyond the foun- dation wall. The rule is that the thick- ness should be 1^ times as great as the largest projection. PREVENT WALL BREAKING 1 REINFORCING FORCES OF WIND ^RODS , I I UPLIFT VACUUM THICK "WALL ^C s^ STRAPPED UPLIFT SLIDING Ö PREVENT WALL OVERTURN â ñ REINFORCING WEIGHT OF SOIL -RODS PREVENTS Since wind may lift or slide houses FOUNDATION i off their foundations, houses must be OVERTURN securely fastened to the foundation. 3 ^LEDGE ON BACK OF FOUNDATION

ANCHOR STRUCTURE TO FOUNDATION

WIN^ REINFORCING -RODS

WIDE TOE ON rz:!?] FOOTING

For masonry walls the fastening device Other jobs of a foimdation wall are should be extended through the foun- to insulate and to moisture proof. dation to the footing. In all cases there Basements have been traditionally used should be a continuous tie extending as cellars to store foods and supplies, as far into the soil as practical. especially in the colder climates. But Foundations acting as retaining walls in recent years, with less need for long must be designed to prevent overturn- term food storage, houses are being ing or breakage. Breakage may be pre- built without basements or with base- vented by reinforcing or by making the ments to be used as family living areas wall thicker. Overturning may be pre- and/or game . If you are going vented by making the wall thicker. to use your basement as a Hving area.

166 you will want a dry basement which upon the cold surface. This is called can be kept at a desired temperature. sweating. The temperature can generally be Sweating creates an atmosphere con- maintained by installing a proper size ducive to the growth of mold and/or heating system. But if you are going to fungi and can be quite objectionable. heat economically, the foundation or This problem generally goes away in basement wall must be of reasonably the winter months when the outside air tight construction to prevent warm air is colder than the inside air. However, from escaping through cracks. Most there are exceptions. One example is people will also want a well insulated moisture being produced in the house wall to achieve maximum economy, and by extensive boihng of water or by comfort. frequent use of hot showers. Another is moisture from the soil soaking through the basement wall and evapo- rating into the air. SLAB FLOOR INSULATION High can be dealt with. will remove several quarts of moisture per day from the VAPOR BARRIER air. But for dehumidification to be -"INSULATION economical and effective, the atmos- phere must be closed. and win- dows should be kept shut. Any outside air getting into the basement will bring more moisture in and cause the to have that much more work to do. ^^yyvwus VAPOR BARRIER Another way to deal with moisture INSULATION is to eliminate cold surfaces in the basement or house. This can be done through insulation. Floors may be covered with felt paper and tile, walls may be insulated and finished. If you insulate the wall or floor, you Since concrete is a good heat con- must provide a vapor barrier to prevent ductor, you must take special care moisture in the air from flowing through when concrete slabs are installed close the insulation to the cold surfaces where to the soil surface. A sheet of rigid it will condense under the insulation. A insulation may be instaUed vertically film, some paints, and several down the inside of the foimdation wall, other materials can be vapor barriers. or between the floor slab and the One common example of moisture foundation wall and then horizontally passing through insulation is the con- under the slab. densation of moisture under a carpet Moisture in basement air is partic- on a basement floor. Many people must ularly troublesome in wet climates. take basement carpets up during the Hot and relatively dry air from outside summer months to avoid such conden- enters the basement where its tempera- sation. ture is reduced by several degrees. As In winter, ventilation can remove air cools, it can t hold as much mois- excess moisture from the basement or ture; thus cooling the air causes it to crawl space. Ventilation becomes ex- become quite humid. If such humid tremely important if moisture is being air comes in contact with an even cooler produced there. But ventilation brings surface such as the wall or the floor of in cold air and exhausts warm air, so the basement, it will become so humid excessive ventilation will carry off a that it will deposit some of its moisture good deal of heat.

167 Ventilation should be used when the paints and coating should also be used problem can't be handled by insulation, over the parging to increase moisture or when periods of high moisture pro- resistance. duction are of short duration. It is especially eflFective when the crawl MOISTURE PROOF F:0UNDATI0N WALL space is not heated.

Ventilation will carry moisture being WATERPROOF COATING evaporated from the warm soil out of ( PAf^lt^) the crawl space. This keeps it from RICH CEMEr^ condensing on the timbers, which PASTE causes mold to grow and results in rotting of the timbers. Make sure your unheated crawl space is well vented in winter. If you have surface moisture leaking Heating the crawl space and insulat- through your basement wall, the most ing the foundation wall can eliminate effective solution is to dig down on the the need for vents, and probably reduce outside of the wall and install a drain total heat loss from the house. In this field below the basement floor. Then way, air from the living area can be parge and paint the wall and backfill used to ventilate the crawl space, and with a coarse aggregate, such as moisture carried out of the soil will cinders, , , or stone. If the humidify the dry air in the living area. drain field can't be emptied by gravity, Another problem is moisture which install a to carry the mois- flows out of the soil into the basement ture away from the bottom of the in liquid form either though the wall foundation wall. or the floor. The smart builder will give Since this solution is expensive, most the foundation every possible advantage homeowners will look for an alternate against ground or surface moisture by: method. • Providing the house with gutters and If soil moisture will flow down along down spouts to carry roof moisture the outside of the basement wall and away from the foundation wall. under the house, such moisture may • Sloping the grade away from the be removed by breaking a hole about 2 house on all sides. feet square and 1 to 2 feet deep in the • Using swales or open drainage to basement floor and using a gravity carry off surface water drain or a sump pump to carry the • Back filling behind the foundation moisture away. wall with porous fill, and providing Several patching and plastering drain tile at the base of the footing materials have been developed for below the basement floor level to drain sealing cracks on the inside of basement moisture away from the house. walls. Most are ineffective. Those that are good will stop the flow in one place, SURFACE WATER REMOVAL but the moisture will simply back up ROOF and find a new flow path. If you can be satisfied with a wet wall, some systems have been devel- oped to keep the floor dry. They collect SWALE^, ^--^SLOPE GRADE OR OPEN DRAINAGE ^ AWAY FROM the water at the base of the wall and carry it to a drain or sump. Using this same collection system, Parging (plastering) the outside of one can reduce the wall moisture by the foundation wall with a rich cement drilling a series of holes near the base paste will prevent moisture which of the wall just above the collection comes in contact with the wall from system. This causes the moisture to soaking into or through it. Water proof flow through the wall at a lower level.

168 MOISTURE CONTROL to the wall with masonry nails, don*t use furring thicker than % inch or nominal 1 inch . Thicker strips are too SLOPE GRADE rigid to conform to the shape of the wall. Too often when driving the last VAPOR BARRIER nail you will loosen the other nails ASPHALT MASTIC GRAVEL FILL which had been securely fastened. If you want thicker furring, use two or DRAIN TILE UNDER FLOOR three layers of % inch strips. With furring strips, electric wires can easily be strung from outlet to outlet and the lower cost bat type insulation MOISTURE CONTROL METHODS may be used. A 4-mil polyethylene UNDER SLAB vapor barrier may be placed over the entire wall. The panel of wall board or other material can then be attached to the furring by conventional methods such as gluing or nailing. If you are building or buying a house, take a little extra care and save Floor slabs can be protected from yourself the enormous problems which moisture by a gravel fill and drain tile are common to poorly installed base- below the floor level. A plastic vapor ments and foundations. barrier placed over the gravel fill and When purchasing a house, check the under the concrete floor is another aid foundation carefully. Look for sloping in keeping soil moisture from flowing or unlevel floors; this can indicate the through the floor into the basement. foundation has settled, timbers have A foundation or basement wall is rotted and/or moved, or that the floor often called upon to be a decorative was not level at the time of construc- surface, equipped with all the conve- tion. You may find small cracks in most niences found in other walls. foundation walls which you can toler- Basement walls can be insulated and ate, but large cracks occur only if there finished in several difl^erent ways. If is excessive foundation movement or you decide to use rigid insulation, you settling. can attach M inch to 2 inches of foam Moisture problems are generally plastic or other materials to the wall seasonal or intermittent. Therefore, with a recommended adhesive. Pref- consider the season and the current erably, the rigid insulation should be a weather when examining the house. vapor barrier or should have a vapor Look for moisture lines on the walls, or barrier attached to it. Some rigid foam for dark or dry mold spots on timbers. panels have a plastic treated paper Check timbers for soft spots, especially surface which stops water vapor. close to the wall and/or floor. Make After insulation is installed, panel sure the grade slopes away from the board or other wall finishes can be at- house and drainage is good. tached to the insulation with a good When you are building, remember grade panel adhesive. Adhesive can that if the builder follows the recom- likewise be used to attach baseboard mended installation procedures, chances and moldings. Electrical outlets may of having a wet basement are remote. be surface mounted or wires may be So insist on recommended installation. counter sunk into the insulation. Find out if there are soil problems Another way is to use furring strips which can cause foundation headaches, on your basement wall, and then attach and seek advice on handling such prob- a panel board to the strips. lems from your State extension engineer If you are going to attach the strips or other consultant.

169 Basements can add economy to your readily. Subsequent drying will lock house. First, they are relatively low the wood into its warped shape. in cost. Basements are cooled by the Paint blistering may be caused by soil in summer, thus reducing the need temperature changes, water, or other for . In winter they factors. Water in or coming through are warmed by the soil, reducing the boards may collect under the relatively heat needed to keep them comfortable. impervious paint layer and raise a blis- For environmental economy, solve ter. The blister may crack and cause the moisture problem, insulate ade- peeling or may subside and leave a quately, and live in your basement in rough spot. all weather. Keep the upstairs just for Many of the water sources and prob- show. lems are easy to spot and correct. For example, condensation of water vapor is almost always a problem in colder climates. One of the best places to look for condensation in a house is on the Preventing Moisture . Damage in Houses Movement of water is controlled by vapor pressure, which, in turn, is con- trolled by temperature if all other fac- rloMEOWNERS CAN USE simple tors are equal. Warm air can hold more procedures that control movement of moisture as vapor than can cool air. water through wood construction ma- During periods of cold outdoor tem- terials to prevent moisture problems peratures, the windows in a house are like decay, warping, paint peeling, or always colder than the air inside the condensation. house. Consequently, when the air Decay is caused by small plants touches the window glass, it is cooled called fungi. Like all living things, and promptly loses some of its moisture fungi need water, almost always more which condenses on the glass. than is present in the air. When wood Now, since all gases move from areas in a house or other structure becomes of high concentration to areas of low damp, the ever present fungus spores concentration, water vapor moves to- come to life and use the wood as food. ward the relatively drier air near the Drying will send the plants into dor- window. It also condenses when it mancy until the next period of wetness. touches the glass and the process Some fungi, those causing what is er- repeats. roneously termed "dry rot," are able The amount of condensation is deter- to transport water over some distance mined by temperature difference and and can work in what appears to be amount of water in the air. The colder dry wood. the window and the wetter the air, the Warping, another common moisture faster condensation proceeds. problem, can occur because one side of If the air is very moist, its dewpoint, a board gains or loses more moisture the temperature at which condensation than the other. Since moisture causes occurs, will be higher. Hence mirrors wood cells and fibers to expand, the at temperature become clouded wettest cells and fibers expand the most in a steamy . and twist the board out of shape. The process of water vapor moving Moist wood is also more pliable than from warmer to colder locations can dry wood, and wet beams or planks also take place in walls that allow mate- supporting a weight will bend more rial to move through them. Here, the movement is much slower. In the win- AxjTHOR H. o. FLEISCHER is Director of ter time the moisture moves from the the Forest Products Laboratory, U.S. Forest warm, inner side of the wall to the Service, Madison, Wis. cold, outer side.

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