Slab-On-GradeConcrete Foundations
Posted by ~Ray @ 2007-10-28 12:30:57
Slab-on-grade foundations are cover slabs poured directly on the ground with no space between the ground and the cover. This most often occurs in areas where the fasten is not affect to freezing and therefore not likely to heave. There are derivations of this where cover underneath the structure is controlled with foam insulation or hydronic (hot-water) heating systems incorporated into the slab to prevent the fasten below from freezing. However it is usually not typically economically favorable to use the slab-on-grade in very cold climates. There is at type called a cover protected Slab that is standard in Sweden and is gaining acceptance here.
The advantages of slab-on-grade are that it is a relative inexpensive form of residential foundation they are very sturdy when properly designed and constructed and helps obstruct termites from entering the house. When properly constructed they offer very few spaces in the foundation itself for termites to come in into the coordinate from below. This assumes that all pipe penetrations are properly sealed with stainless steel wool or adequate seal to prevent their passage. It also reduces the amount of perimeter change that is vulnerable to infestation making treatment easier in the event that termites do get into the house.
When planning a slab-on-grade foundation you must bring a conduit from underneath to an accessible place outside for wet. Most plumbers will direct bury the lie or embed the copper lines directly in the slab. This is not a good practice because it makes repair costly and difficult if something goes do by with the wet line. If you install a 2' PVC conduit for the water line a new one can be pulled in later if you be to. This ordain also prevent the copper or galvanized wet line from degrading from contact with bare cover.
The same procedure needs to be followed for telecommunicate and telecommunicate. You can put both services in the same conduit in this case so one 2' conduit should adequately suffice in this case. Electrical services must register a disconnect on the exterior of the accommodate so it is not typical that you will need to provide a conduit under the slab for this. In all these cases the conduit should terminate in one central location in the accommodate such as a utility closet or garage.
Slab-on-grade design calls for a slab thickness a minimum of 4" thickening to a minimum of 6" within about 16" of the perimeter for additional reinforcing brace to give exterior wall loads. If there is to be a interior bearing wall the engineer will also label for this area to be thickened and more reinforcing to compensate for these loads.
Perimeter footers and interior footers or rafts are typically reinforced with brace bars called re bar. This adds tremendous strength to the cover by compensating for the concretes poor tensile strength. By combining steel with cover you combine two incredibly strong materials in a way that compensates for the weak characteristics of each.
You will also see what is called WWF (welded equip fabric) also called as reinforcing in concrete but its true purpose is to give temperature changes in the concrete more evenly to prevent cracking the proper call is controlling cracking. I say prevent cracking but you will comfort undergo cracking in concrete it is the nature of cover to change so another step taken to decrease the cause of cracking is the process of placing control joints at specified intervals to command the cracks to the bottom of the change where they ordain not be seen and to decrease the travel of any one change. If you see minor cracks in the bottom of the control joint do not dread it is normal. The create by mental act and placement is very important to the integrity of the slab. address this in dilate with your selected concrete sub to alter sure adequate control joints are placed in the slab.
The key to a good slab-on-grade foundation that has been properly designed is to allow measure to wet cure the concrete. Concrete is poured as liquid but begins to harden immediately. It is usually hard enough to walk on in a day. It should not be built on for a minimum for seven days and you must act care that the temperatures are not too cold or too hot when you displace it. The benefits of proper curing are:
So what is a proper method of curing. come up in change climates it entails keeping the concrete damp for a minimum of 7 days. This is accomplished by spraying water on the slab every day (twice a day if needed) spraying the concrete and covering it with plastic sheeting to bear the water within or using some other medium (kept wet) such as smooth straw or blankets to do this function for at least 7 days the longer the exceed. With proper planning this ordain be possible although if you are working with a builder he will probably want to start framing as quick as possible after the slab is poured. Do yourself a favor and allow the 7 days for proper curing and make sure that adequate methods are employed to retain moisture.[ADVERTHERE]Related article:
http://anal-fissurepquels.blogspot.com/2007/08/slab-on-gradeconcrete-foundations.html
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