Being exposed to high concentrations of radon for long periods of time can put you at risk for lung cancer. Health Canada advises taking measures to reduce radon levels when radon concentrations exceed 200 Bq/m3. Radon exposure is linked to roughly 16% of lung cancer deaths in Canada, and is the second leading cause of lung cancer after smoking. The gas infiltrates houses through cracks in the slab. Radon is a naturally-occurring radioactive gas that is produced when uranium that is present in the earth's crust starts to disintegrate. RADON GAS EVACUATION with a slab on grade foundation: The top of the formwork can be used as a gage to delimit the height of the concrete to be poured.Snap a levelled chalk line on the interior of the formwork to indicate the height of the concrete to be poured.Defining the boundaries of the concrete slab can be done easily with wooden stakes driven into the ground and a string line laced at a right angles.The pipes should then be covered with a small amount of crushed stone. Dig several small trenches for the insertion of perforated pipes that will be used for radon evacuation purposes (see "Radon gas evacuation" below).Vibratory plate compactors work best and are available at most construction rental outlets. Gradually fill and compact the rest of the trench as well as the undisturbed ground in the centre before spreading crushed gravel over it.Cover the trench with a layer of permeable backfill material.The barrier will prevent sediments from entering the drain while the gravel provides sufficient drainage. Spread crushed gravel around the French drain and install a geotextile over it.If dealing with high iron bacteria content, it is a good idea to build an access pit at the surface for cleaning purposes.This involves the inclusion of a compacted layer of stone beneath footings. Notes for Drains under FPSF or Slab on Grade:ġ) Some experienced builders prefer rigid plastic French drains over flexible grooved drains to increase durability.Ģ) Including an accessible cleanout T-junction is a nice added feature as they allow for easy maintenance in the case of sediment buildup.ģ) When dealing with an iron bacteria problem, a rubble trench footing can potentially be a more lasting solution than conventional French drains. Cover the French drain with a layer of crushed stone, then cover it with a geotextile to prevent the accumulation of sediment.If that is not possible it should be connected to a sump pump. At the bottom of the foundation drainage trench, install rigid French drain piping (weeping tile) that can drain to a lower level. ![]() DRAINAGE under Slab on Grade Foundations: Excavated topsoil should be placed in a designated spot and protected from washing away with a waterproof covering such as a tarp. Notes for excavating a Slab on Grade foundation:ġ) When beginning with a rubble trench for the load bearing part of a foundation (as per instructions from an engineer), pit run gravel can be a more affordable option than crushed stone.Ģ) Ask your contractor to protect topsoil for future use. See our page on raft slabs as an alternative to a thickened edge slab on grade foundation. Depths, widths and backfill specifications will be provided by engineers. ![]() In this case, a trench is dug around the perimeter of the future house where there will be footings.
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