Should i put plastic under concrete

Vapor barriers have varying degrees of permeability, expressed in perms. The higher the number, the more permeable the material. Impermeable vapor barriers are those with a rating of 0. Vapor barriers are less permeable than vapor retarders. The acceptable degree of vapor barrier permeability depends on the application. While a water vapor permeance of less than 0. However, the vapor barrier under the slab must have a lower degree of permeance than the flooring or floor covering above the slab.

Watch are video to find out what you need to know about concrete vapor retarders. One word: adhesives. All of the problems associated with moisture vapor movement in a concrete slab will go away in time as the slab dries, as long as there is no source of additional water into the slab. Since the most common source is moisture in the ground beneath the slab, the solution is to completely take the ground out of the equation, by sealing the bottom of the slab.

Find out where to buy vapor barriers and other problem solving products. The best way to accomplish that is with a vapor barrier under the slab. Vapor retarders have been used since the s. Recently, though, research has shown that the old traditional layer of 6-mil Visqueen polyethylene plastic under the slab is seldom effective for two main reasons:. Thin plastic like this is often called a vapor retarder—meaning it slows the vapor down but doesn't stop it.

For all three classes of vapor retarder, the permeance a measure of how much vapor can pass through must be less than 0. Sledgehammer is the best tool to use if the slab of concrete is three inches thick or less. Dig at the base of the slab to find the bottom. Air circulation will increase the evaporation rate of the water from the concrete. Heat will also increase the evaporation rate.

Vapor barriers are usually best installed on the side of the wall that experiences the hotter temperature and moister conditions: the inner surface in colder climates and the outer surface in hot, humid climates. In existing spaces, oil-based paints or vapor - barrier latex paints offer an effective moisture barrier.

Should I put plastic under my concrete slab? Category: home and garden indoor environmental quality. If the ground is dry, plastic prevents water from being sucked out of the concrete while curing.

You can always wet the ground prior to laying the concrete for a similar effect. Should I insulate under my concrete slab? How do you prepare the ground before pouring a concrete slab? How do you install moisture barrier under concrete slab? Can water come up through a concrete slab? How much insulation do I need under a concrete slab? How much gravel is needed under a concrete slab? Can you pour concrete over dirt? Pour concrete over a solid, well-drained base.

Is gravel needed under concrete? Can I use plastic sheeting as a vapor barrier? Should you put plastic under your house? Waterproofing a slab on ground is quite a complex subject. Vapour barriers are the black or orange plastic that builders put under residential house slabs. They do this for two main reasons:. To install a vapour barrier, roll out the roll of black plastic on top of the compacted sand subbase and before placing your slab on ground reinforcement.

Waffle slabs require vapour barriers too and here are some photos that show a few waffle slabs with vapour barriers — again before the concrete is poured. The requirements to have a vapour barrier under a concrete slab come from the NCC — the National Construction Code Australia which is free when you register and the Australian standard AS for residential footings and slabs which you have to buy.

So yes, a vapour barrier is required under a concrete slab for a Class 1 building a dwelling and for Class 10 eg a garage where the slab is continuous with the dwelling. In New South Wales, Clause 3. There is no excuse not to comply and we join the call for ALL certifiers to be checking that the damp-proof membrane complies with the current requirements of the NCC and AS In fact, most professional shed slab builders will install a polyethylene membrane under a shed concrete slab even if it is not specified.

The reason is that the vapour barrier stops moisture from the wet concrete escaping into the ground under the concrete. When we call vapour barrier in our drawings we call it up as 0.