Is a vapor barrier necessary 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.

Should you put a vapor barrier under a concrete slab?

If you have a concrete floor that's in continuous contact with a source of moisture, you're going to have problems. This is why a vapor barrier under concrete is essential. Vapor barriers are a way to keep moisture from getting into the concrete.

How thick should a concrete slab be for vapor barrier?

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.

Is it important to put plastic under concrete?

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.

Where do you put vapor barrier under concrete slab?

Why do you need a Vapour Barrier Under Concrete Slabs - The Structural Why Files aswers the question

How do you vapor barrier under a slab?

These vapor barriers can be installed over tamped earth, sand or aggregate base: simply unroll and completely cover the area receiving the slab, overlap the seams by 6 inches and seal by heat welding or with sealing tape. All exposed penetrations should also be sealed.

What do you put under concrete slab?

What Material is Used for a Slab Base? The base in concrete construction is usually a form of crushed stone. Most concrete contractors want a mix of coarse and fine aggregate to create a compactable base that is going to be safe for settlement and drainage.

Do you need vapor barrier for outdoor 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.

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.

Do I need vapor barrier?

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.

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 basement floor need vapor barrier?

All for lack of an affordable, easy-to-install basement floor vapor barrier. Climate plays a part: In dry climates, contractors often skip the vapor barrier. But in average to humid climates, and anywhere ground water is abundant, an impermeable vapor barrier is essential.

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.

Where should a vapor barrier be installed?

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.

Can concrete be poured on plastic?

For temperatures in between, use clear plastic sheeting. While plastic sheeting is highly effective in helping concrete cure without cracks, there is a downside: The concrete will be discolored anywhere the plastic touches it.

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 you need subfloor over concrete?

Do I Need a Subfloor Over a Concrete Slab? While a subfloor is not necessary to add structural strength when you'll be laying finish flooring on top of a concrete slab (as in a basement remodel), subflooring over concrete offers two other advantages: Dampness control.

Can you lay a solid wood floor on concrete?

You can also install a solid wood floor over a concrete subfloor by floating it on an adhesive backed underlay such as Fast Fit Peel & Stick Underlay. This has adhesive on one side which the solid wood floor is laid onto. Before you lay down the underlay you will need to first lay a damp proof membrane.

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.

Do you need 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.

What is the best base under concrete?

What is the Best Base for a Concrete Slab? Most people build a driveway or a patio so in that case, a good choice would be a mix of coarse and fine aggregate which will create a compactable base. Overall, a mix of crushed stone and stone dust is the best base material for any concrete flatwork.

Should I put gravel under my concrete slab?

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.

How do you secure a vapor barrier to concrete?

Stick the vapor barrier material to the foundation seal tape and then use mechanical fasteners to hold it forever. Drill holes through the plastic and through the seal tape into the block. If you drill through the seal tape you will prevent the plastic from peeling off when you remove the drill.

Do concrete slabs need footings?

A concrete slab foundation needs footings in order to: Provide support to the walls of the building built on the foundation. Resist heaving and shifting due to freeze/thaw cycles. Prevent water runoff from undermining the slab.