If you live in a colder climate, your foundation will be a "Pier and Beam" or a "Basement" foundation due to the depth of the frost. In warmer climates a "Slab on Grade" or "Monolithic" concrete foundation is more popular as there is surface freezing only for short periods. The cost of a slab on grade foundation is much less expensive and if properly constructed, it has the same longevity.
A slab on grade or monolithic foundation is one continuous concrete slab. The grade beams and the slab surface are one unit. If there is fear of a fault or a history of foundation failures in the area due to very poor soil conditions, bell bottom piers drilled down to stable soil would be an excellent precaution.
First you want to prepare the substrate to provide a stable pad on which the concrete foundation will rest. Determine the perimeter of the house and bulldoze a six to eight inch layer of grass and unstable top soil down to what is termed 98% stable soil. If there has been unknown fill brought in over the years, you may want to remove up to twelve inches.
Next you want to establish the height of your finished floor. If you have a fairly level lot, customarily the finished floor level will be eighteen inches higher than the crown of the street in front of your house. If you are building on a hillside, make sure that during heavy rains the water will hastily drain from your slab.
Your fill should be what is termed, 'Sandy Loam" or in construction terminology, "Select Fill". This is a very stable soil that doesn't expand and contract from a wet to a dry season. It will compact and support a slab foundation with very little heaving. Be sure the entire fill is consistent as you do not want a differential of movement from one end of your slab to the other.
The sandy loam (select fill) soil will compact very easily and the best manner to accomplish this is to have a bulldozer spread the soil as it is being dumped and let the pneumatic tires of the dual-axle trucks run over it as each lift is applied, however you must use a compactor to assure thorough compaction. If the soil is extremely dry, as you are spreading the dirt apply a small amount of water to aid in the compaction.
The normal thickness of a residential slab is four inches; therefore you want to bring the select fill within six inches from the final grade, then bring in a two inch layer of sand for a cushion between the pad and the concrete slab.
Wood forms are built to the desired grade and grade beams are dug. These beams are normally eighteen to twenty four inches deep and twelve to fourteen inches wide. If your foundation plans have been properly engineered; the size of the beams, how many and their placement will be specified. A vapor barrier using 6m poly-film or an equal should be placed on top of the prepared substrate. The reinforcement steel will also be specified by the engineer and should be strictly adhered to.
In the case of heavy rains, be sure to remove any water from the grade beams and let dry for a couple of days. A light rain is of no concern and will not damage your pad.
The final stage is pouring the concrete in the beams and forms. Do not let the concrete finishers water down the ขายอาคารพาณิชย์ concrete; pour it as dry as possible yet allowing enough water to enable slow curing and proper finishing. On a hot summer day, once the surface has hardened enough, set up a water sprinkler to cool down the hot concrete and slow down the curing. If the surface cures much faster than the rest of the slab, you will have some surface cracking.
ไม่มีความคิดเห็น:
แสดงความคิดเห็น