Do you need a vapor barrier under a concrete slab?

Exterior concrete slabs or those in unheated structures don't require a vapor retarding barrier. However, if the surface will be sealed with an impermeable membrane or product, there should be a vapor barrier under the pad.

Where do you put vapor barrier under concrete slab?

Do you need plastic under a concrete slab?

Plastic is a moisture barrier generally to stop ingress from beneath the slab. If this is outdoor in an exposed area it probably doesn't matter. I'd probably use plastic if the area is moist with little sun, just to alleviate any algae growth. It's outdoors, north facing, lots of sun.

What is the minimum vapor barrier thickness beneath a slab?

The American Concrete Institute's Guide for Concrete Floor and Slab Construction recommends that the thickness of the vapor retarder be at least 10 mils.

What do you put under a concrete slab?

Because concrete is a very porous material, it will absorb any moisture that it contacts. This can cause pooling. Without crushed stone, pooling water will settle under it and erode your slab. Adding a layer of crushed stone will add proper drainage, as well as create a barrier between your slab and the ground.

Why do we install a vapor barrier under slabs? (018)

Do you need a membrane under concrete?

These days, damp proof membranes are required in the construction of all new buildings to prevent rising damp. These strong and highly durable Polyethylene 1200 Gauge DPMs are sandwiched between the hard core and concrete slab to form an impermeable layer.

Do you need a vapor barrier under concrete patio?

Exterior concrete slabs or those in unheated structures don't require a vapor retarding barrier. However, if the surface will be sealed with an impermeable membrane or product, there should be a vapor barrier under the pad.

Can you pour concrete over vapor barrier?

However, the current practice recommended by the American Concrete Institute is to apply a heavy grade, non-penetrable vapor barrier (or retarder) with the lowest possible permeance for the application over a layer of granular fill (crushed rock, gravel, etc.). The concrete slab is then poured on top of it.

Do I need a vapor barrier between concrete and wood flooring?

A common question that DIYers ask is, "I'm installing a new floor on-grade, a cement slab. Do I need a vapor barrier for hardwood floors?" The answer is YES! Moisture can destroy hardwood flooring. It causes cupping, warping, and even mildew if not treated.

What should I put between wood and concrete?

Anyplace where wood meets the ground or concrete, the lumber must be pressure treated. For additional moisture protection, a gasket or strip of closed-cell foam can be installed between the concrete foundation and the sill plate.

Is vapor barrier necessary?

A vapour barrier is an important component in building construction. Its purpose is to help prevent water vapour from reaching building walls, ceilings, attics, crawlspaces or roofs, where it can condense and cause building materials to rot or grow mould.

Can concrete flooring be installed over wood?

A decorative concrete flooring material can be installed over an existing concrete slab, a plywood subfloor or a 3/4-inch solid hardwood flooring. When it comes to solid wood, both strip and plank flooring are acceptable as long as they are in good condition.

Do I need a vapor barrier and underlayment?

Very often, particularly in a below-grade installation on a concrete basement floor, a vapor barrier is recommended in addition to the underlayment. That vapor barrier would go between the subfloor and the underlayment.

Is gravel needed under concrete?

You do need gravel under a concrete slab, footing, or patio. Gravel provides a solid foundation for your concrete as it can be compacted. It also improves drainage, preventing water from pooling beneath the concrete.

What kind of plastic do you put under concrete?

The most commonly used vapor barrier under concrete slabs is polyethylene (poly) plastic sheeting with a thickness of 10 mil or 15 mil. All Americover Vapor Barriers are composed of virgin polyolefin resins and offered in 10 mil, 15 mil, and 20 mil.

How do you insulate under a concrete slab?

For under-slab applications, the rigid foam insulation typically should be installed over a gravel base, with a poly vapor diffusion retarder between the gravel and insulation. Additional insulation is applied along the edges of the slab, because that is a primary surface for heat loss.

How do you install a vapor barrier on concrete?

Does vapor barrier go above or below slab insulation?

The industry consensus is that underslab vapor barriers should be installed if the slab will be in conditioned space, or if the slab will be covered with a moisture sensitive flooring system. The underslab barrier should be less permeable than the floor covering.

Does a 200 square foot garage floor have to have a vapor retarder under the concrete slab?

Concrete Garage Floors & Vapor Transmission

We find ourselves having to explain that the vapor retarder wasn't required or necessary for a concrete garage floor poured at or above grade. The 2012 International Residential Code states: R506.2.3 Vapor Retarder.

Can moisture come up through concrete slab?

Humidity—warm and humid air condenses into surface moisture when it comes into contact with the cool surface of your concrete floor or slab. Faulty/Missing Vapor Barrier—moisture from the ground can seep up and through the concrete.

Can you get rising damp through a concrete floor?

Damp affecting Concrete Floors

The reason for this is that concrete is a very porous material meaning that water can rise through capillaries and therefore lead the property to suffer from having damp floors.

Can water come up through a concrete slab?

No, water isn't going to soak up like a sponge, but concrete does allow water to seep through when there is enough. Concrete also cracks, and those cracks will be the first routes of seeping water as it leaks through the slab.

What is the minimum thickness of concrete floor?

A residential concrete floor should be around four inches thick. If you plan on your concrete floors handling heavy loads, five to six inches is more appropriate. With that said, the minimum thickness of concrete flooring is around two inches, although we wouldn't recommend choosing to go that thin.

Can I pour concrete over plywood subfloor?

If you've got a plywood subfloor, like many buildings do, you can leave it in place and apply self-leveling concrete directly on top of it. Once the plywood subfloor is covered, just apply the finish you want to achieve the desired look.