Gravel and vapor barrier under slab
Are you planning to break ground on a new project soon and begin laying the slab? Don't forget to properly protect your future home from water and air intrusions through your slab. Concrete, although very solid, is also slightly porous.
The tiny pores in your slab can wick moisture from the ground into your home. In order to preventsuch an intrusion, we suggest a true 4 inches of gravel be applied beneath your slab. Between the gravel and slab a solid vapor barrier should be installed – a 6 ml thickness of plastic will do the trick. The gravel will act as a capillary break, separating your slab from the moisture filled earth beneath and prevent the slab from wicking it into your home.
Applying gravel will also allow water to be more evenly distributed into the ground beneath your home. With the slab applied directly onto the dirt, during a rain the edge of your slab would be soaked while the middle would be dry. With gravel installed under the slab, the water at the edge will be able to move through the holes created by the gravel and therefore be able to reach a greater surface area of the dirt beneath. This added surface area will allow water to dissipate from beneath the foundation of your home more quickly.
The waterproof membrane between the gravel and slab is equally important. First and foremost it prevents water from ever directly touching the slab from beneath. Secondly, the vapor barrier will be a flat surface on which the concrete is laid, increasing the overall strength and reducing the risk of a crack. Here in the Georgia red clay, this is especially important because of the low levels of water penetration through the dense soil.
Luis Imery Luis Imery, through his business the Imery Group, is a full service construction, home energy performance, green certification and real estate group specializing in infusing sustainability in every facet of the real estate cycle. Its construction division has become pioneers in the Athens, GA area in green building of speculative, custom and design-built construction. Just in 2011 they have over 110 units slated for green certification under the EarthCraft program. www