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why put gravel under concrete slab on grade

Compact Fill Under Slab - askthebuilderDEAR TOM: Un-compacted fill under concrete slabs of any type is a recipe for disaster. The slab could be for an entire home, it might be an exterior patio slab, a front porch slab, a driveway, etc. Concrete is an amazing material, but it has an Achilles heel.How much gravel under concrete? - TractorByNet26.11.2002· Not just ordinary gravel. What is needed is processed gravel of the type that your county will put on its gravel roads. This gravel has a wide gradation of material size including some clay fines. Under proper compaction techniques, ie. plate compactor and correct amount of water, a well compacted gravel base will feel like concrete itself.How to Pack Down Rock Before Pouring .Gravel is especially important in clay soil because it doesn't drain well, which results in water pooling under the concrete slab and slowly eroding the soil as it finally drains. Gravel allows ...How to Prepare the Ground Before Pouring .Determine the proper depth by establishing the height of the concrete slab. Add 2 inches to the depth for gravel if the soil is normally moist or has a high concentration of clay. Most concrete slabs will sit 1 to 2 inches higher than the dirt and 2 to 3 inches below the surface of the dirt, making the needed depth of the hole 3 to 5 inches.

The Dirt on Below-Grade Insulation – Insulfoam

Contractors are increasingly called upon to install rigid foam insulation under concrete slabs and on building foundations. Up to one-quarter of a building's energy loss is due to lack of insulation in below-grade areas, including the foundation and under slabs. Now that high-performance building envelopes are common above ground, the relative amount of total heat lost below grade will grow ...what do you use under concrete?We don't use recycled concrete under any concrete floors we install. We use mostly gravel and sometimes the stone. I would also recommend a vapor barrier of 6 mil poly on top of the stone before you pour the concrete. Click here to post comments. Join in and write your own page! It's easy to do. How? Simply click here to return to Concrete Floor Questions. If you liked this, please share ...Concrete Floor Problems | Building Science .26.05.2008· Photograph 2: Slab-on-Grade Done Wrong —Note the layer of granular material over the top of the plastic vapor barrier. Liquid phase water will be held by the fines in the granular material creating a reservoir of water that can only dry upwards into the slab leading to problems with floor finishes and floor coverings.

why sand under concrete? - Fine Homebuilding

19.08.2004· I'm preparing to pour a finish concrete foor, slab on grade. The structural plans call for 4″ compacted gravel base, insul-tarp vapor barrier, 2″ of sand and 4″ of concrete. What purpose other than a base for the concrete does the sand serve? Why use it when yopu have thick insul-tarp?3 Reasons Why It's Important To Use Crushed .28.04.2014· Concrete may seem strong, but after many years, elements, and pressure, it will eventually crack. So in order to make your concrete last as long as your money that went into it, adding a layer of crushed stone under a slab of concrete will increase the life of your investment. Here are 3 reasons why a layer of crushed stone is important to the life of your concrete:Do you need rebar for a 4-inch slab? - QuoraIt all depends on the size of the slab and whether the slab is on grade. A concrete slab reinforced with rebar or welded wire fabric should have a minimum 1 1/2 inches of clear cover between the reinforcing and the top of the slab. If it is a susp...why is it important to have gravel under a .24.03.2010· For the best answers, search on this site https://shorturl.im/avT7K. I would suggest using 6" of compacted sand and 4' of concrete. It is necessary to have the original concrete floor broken if not it should be broken to allow any trapped moisture to drain to the sub grade under the original floor.what do you use under concrete?We don't use recycled concrete under any concrete floors we install. We use mostly gravel and sometimes the stone. I would also recommend a vapor barrier of 6 mil poly on top of the stone before you pour the concrete. Click here to post comments. Join in and write your own page! It's easy to do. How? Simply click here to return to Concrete Floor Questions. If you liked this, please share ...

compacting gravel under a slab - JLC-Online .

07.12.2004· Re: compacting gravel under a slab Tucker: With 2 to 3 feet of rock, I fail to see why you need either poly or insulation under the slab, I think I would opt for the "oozing" and the thickening effect of the "waffle" bottom, I would think that structurally it turns a 3 1/2" slab into something more like a 6 or 8" slab from a structural standpoint.Slab on Grade vs. Pier and Beam – Abry Brothers | .The first, and perhaps most common, foundation type is a slab on grade foundation. A slab on grade is, essentially, a slab of concrete poured into a form that rests on the ground. There are two basic types of slab foundations: Monolithic foundations and stem wall foundations (or chain wall foundations – depending on which part of the country ...How to Prepare the Ground Before Pouring .Determine the proper depth by establishing the height of the concrete slab. Add 2 inches to the depth for gravel if the soil is normally moist or has a high concentration of clay. Most concrete slabs will sit 1 to 2 inches higher than the dirt and 2 to 3 inches below the surface of the dirt, making the needed depth of the hole 3 to 5 inches.How to build a Slab-on-Grade - EcohomeWhy build on a slab instead of a basement? To save money and carbon emissions, and have a healthier and more durable house. For a detailed guide on choosing between a Slab on Grade or a Basement for a home foundation see here, but we'll give conclusions below. Typically, the construction of a single family home in Canada & North America starts with a poured concrete footing followed by an 8 ...Placing a Concrete Foundation on Rigid Foam .23.12.2014· Compacting the gravel base for the foundation slab. On top of this base goes the radon mitigation system, the slab foam insulation layer, the vapor barrier, and then the concrete slab-on-grade. Regarding pipe penetrations of the slab assembly, it is important to space pipes to facilitate sealing of individual pipes to the vapor barrier.method of statement for slab on grade - .Preparation and Installation Slab On Grade Footing . A. Clean the area of any loose materials prior to start any work make sure that the compacted fill to received concrete is approved by the consultant Engineer. B. Check the dimensions and elevations from the approved shop drawing. C. Apply termite control according to manufacturer's recommendation by using spray on the back filled soil to ...All About Foundations Guide | The Home Centre03.02.2017· Slab foundations are constructed of concrete that is usually 6 to 8 inches thick. The home is then sited on the slab. The construction process includes gravel being spread first to facilitate drainage underneath the concrete and the home. Usually, pipe and utility hookups are installed through the concrete in the slab. Rebar is occasionally used for added support, which may be in the concrete ...Subgrades & Subbases for Concrete Slabs - The .22.11.2017· Almost 20 years ago, Concrete Construction investigated the effect of using a layer of loose (uncompacted) sand directly beneath a concrete slab and concluded that this practice contributed to "more later-age cracks and poorer joint performance." Here are the reasons not to use a sand layer: · Difficult to maintain a flat, level sand surface during concrete placement · Difficult to ...

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