Best answer

Water vapor will always move from a high relative humidity environment below the building into an area of low relative humidity – even through concrete.

That's why nearly every expert in the concrete industry recommends a below-slab vapor barrier to stop the vapor drive of water upward and into your building envelope..

Answered by: akhtarvahid Date created: Jun 24, 2022

Do I need a vapor barrier behind cement board in shower?

Asked By: Mạnh Quyết Nguyễn Date created: Jun 09, 2022

Moisture barriers stop that water or vapor from getting any farther and potentially rotting your studs, the drywall or greenboard installed behind the enclosure. They are required beneath your shower pan and behind your shower walls.

Answered By: Sebastian Krysmanski Date created: Jun 09, 2022

How many bags of concrete do I need for a 6x6 slab?

Asked By: Poul Kruijt Date created: Jun 09, 2022

0.667 cu. yds. How many concrete bags would I need for a 6 ft x 6 ft x 6" slab? 29.9 x 80lb Concrete bags.

Answered By: stema Date created: Jun 09, 2022

Do you need stone under a concrete slab?

Asked By: Jamie Hutber Date created: Jun 19, 2022

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.

Answered By: Ilya Gazman Date created: Jun 20, 2022

How many bags of concrete do I need for a 4x8 slab?

Asked By: Grant Miller Date created: Jun 08, 2022

Your project is 32 square feet at a depth of 4”. Here is the quantity that you will need for your slab. Quikrete Concrete Mix: 24- 60lb bags.

Answered By: dfeuer Date created: Jun 09, 2022

How do I keep my concrete slab from sinking?

Asked By: Justin Date created: Jun 22, 2022

How can I prevent my concrete from sinking?Seal all open cracks and joints with a polyurethane or silicone caulk. ... Make sure downspouts are discharging at least five feet away from any concrete slab – the farther the better.More items...•

Answered By: BFree Date created: Jun 23, 2022

How do I get rid of rats under my concrete slab?

Asked By: turivishal Date created: Jun 12, 2022

Answer: If the patio slab is not connected to the house slab you can use a Giant Destroyer to help eliminate the rat. If there are many tunnels or if it is in an area where you cannot seal up the entrances you may want to consider using rat poison baits instead such as Fastrac or Contrac.

Answered By: Klas Mellbourn Date created: Jun 15, 2022

Is concrete block waterproof?

Asked By: jfriend00 Date created: Jun 11, 2022

Waterproofing Concrete Block Foundations. Concrete blocks and cinder blocks are much more permeable to water and water vapor than poured concrete. ... Block foundation walls will provide only a weak barrier against capillary water seepage and water vapor.

Answered By: Anders Abel Date created: Jun 13, 2022

How do you waterproof a flat concrete roof?

Asked By: RanRag Date created: Jun 17, 2022

Step 1 - Clean Your Roof. In order to successfully seal your roof, you first need to start with a clean surface. ... Step 2 - Carry Out Minor Repairs. ... Step 3 - Use Seam Tape. ... Step 4 - Coat With Primer. ... Step 5 - Spray on a Vapor Barrier.

Answered By: Sanjayrajsinh Date created: Jun 19, 2022

Do you need to seal a concrete floor before laying laminate?

Asked By: Alan Date created: Jun 09, 2022

You don't need to seal a concrete floor before installing laminate; however, to prevent moisture from the concrete floor from affecting your laminate, install a vapor barrier of polyethylene film. Install this barrier even if the concrete subfloor is covered by vinyl, linoleum, terrazzo or ceramic tile.

Answered By: gregory Date created: Jun 10, 2022

Do you need plastic behind cement board?

Asked By: Louise Davies Date created: Jun 15, 2022

Their online instructions/diagrams show no use of a vapor barrier. You should, so that any moisture that gets behind the cement board runs into the tub or shower instead of into your wall cavity (causing rot or mold/mildew).

Answered By: tscizzle Date created: Jun 17, 2022

Related Question Answers

Vivin Paliath

Professor

Do you need a vapor barrier behind cement board?

You still need a vapor barrier with cement board, although in this case the barrier can go behind the board. Cement board is heavy enough and breathable enough to take the moisture without a problem. By having the vapor barrier behind the cement board you stop the moisture going further into the wall.

Misha Zaslavsky

Professor

Do you need to put a vapor barrier behind cement board?

You should NOT place a vapor barrier BEHIND the backer board. Where, pray tell, would any such collected vapor/water go? Answer:There's nowhere proper for such moisture to egress. The current best practice is to place waterproofing OVER the backetboard and just UNDER the tile.

lawrence-witt

Professor

Do I need rebar for small concrete slab?

You do not need rebar for any slab if you make it thick enough and space the joints properly. Rebar in jointed pavement is there to counter the cupping effect of thermal expansion. I always recommend the use of rebar or at least rewire. Any concrete slab can crack.

Mina Gabriel

Professor

Can I pour concrete around cast iron pipe?

You could just add a couple inches of sand, enough to handle the vapor barrier and then cover the pipe with a couple layers of plastic or roofing material and place the concrete right over the pipe.

Prafull Ladha

Professional

Can plaster walls be insulated?

If your historic house has original plaster walls, you should not blow insulation into the exterior walls. Old houses with plaster walls have no vapor barrier under the plaster to stop moist air from saturating the insulation. Instead, plaster walls are designed to allow the free exchange of air and moisture.

Sridhar

Professional

How do you install moisture barrier under concrete slab?

Most exterior slabs do not need a vapor barrier. ... In general, place the concrete slab directly on top of the vapor barrier, with the subbase below. ... The vapor barrier can be placed under the subbase, if the building is closed in when the dry subbase material is placed.More items...

Jens A. Koch

Professional

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

It is rolled out between the actual laminate flooring planks and the subfloor.

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..

Jeff Mercado

Professional

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

Despite a successful moisture check and the presence of an underground moisture barrier, you still need additional protection from water vapor before laying a wood floor. Sheets of 6-mil thick polyethylene plastic, overlapped with seams taped, is one means of providing that moisture barrier.

clstaudt

Professional

Do I need mesh in my concrete slab?

Concrete is strong in compression, but not under tension. So, if it flexes, like a slab with a vehicle on top of will do, it cracks at the bottom whre the flexing becomes tension. ... Mesh will help mitigate the chances of cracking of the slab due to differential settlement.

yahavi

User

Do I need underlay on concrete floor?

Concrete bases need an underlay with a moisture barrier, a damp proof membrane (DPM) or a separate barrier to protect the floor from damp. If the sub-floor is wooden the choice of underlay will depend on what is being laid on top.

stuartd

User

Do plaster walls need insulation?

If your historic house has original plaster walls, you should not blow insulation into the exterior walls. Old houses with plaster walls have no vapor barrier under the plaster to stop moist air from saturating the insulation. Instead, plaster walls are designed to allow the free exchange of air and moisture.

zed_0xff

User

Do plaster walls smell?

plaster is not a vapor barrier, so any odors in the walls can get in. it's good for the longevity of the plaster since it can breathe (if it gets wet, it can dry, for instance), but it won't keep the odors out.

Joran Beasley

User

How concrete flooring is done?

Anatomy of a Concrete Floor This layer is covered with a vapor barrier sheet that prevents moisture from moving up into the concrete. A welded wire fabric mesh sheet is then placed over that in order to aid with adhesion. Finally, the concrete slab is poured directly onto these layers.

haccks

Guest

How do you keep water from seeping on concrete floor?

Plastic drainage mats, or dimple mats, allow air to circulate under the flooring and provide a moisture barrier.

They also provide an insulating layer of air that separates the floor from cold concrete, reducing the potential for moisture damage from condensation or water vapor migrating through the concrete..

hilberts_drinking_problem

Guest

Should you seal concrete before laying laminate?

You don't need to seal a concrete floor before installing laminate; however, to prevent moisture from the concrete floor from affecting your laminate, install a vapor barrier of polyethylene film. Install this barrier even if the concrete subfloor is covered by vinyl, linoleum, terrazzo or ceramic tile.

Omu

Guest

Does concrete stop radon?

Remember that even several inches of concrete cannot stop radon. Some builders believe that the plastic vapor barrier under the slab will stop radon. Although it is a part of the "radon resistant" construction, it merely reduces the flow of soil gas.

Shrey Joshi

Guest

Do I need a permit to pour concrete in my back yard California?

In regards to your question, under the 2002 County of Los Angeles Building Code, section 106.3(15) states that a building permit shall not be required for “Platforms, walks and driveways not more than 30 inches (762mm) above grade and not over any basement or story below,” and as such, the driveway construction method ...

Rocket Hazmat

Guest

Do I need a permit to pour concrete in my back yard NYC?

In general, if you are doing any work which is going to modify your floor plan, then, you do need a permit. If you are going to pour concrete for a patio in your backyard, then, yes, you do need a permit.

Andrei Solero

Guest

How do I stop my concrete sinking?

How can I prevent my concrete from sinking?Seal all open cracks and joints with a polyurethane or silicone caulk. ... Make sure downspouts are discharging at least five feet away from any concrete slab – the farther the better.More items...•Dec 21, 2018

Lars Blumberg

Guest

How much concrete should I get around my pool?

Table and chairs for up to eight requires a minimum 12' x 12' concrete slab. Small end tables and chairs do vary on size of the table. For concrete purposes we generally recommend 5' x 5' concrete slab. Tanning lounger/ Chaise loungers need a minimum of 8' of concrete off of the swimming pool.

Aristotle Pagaltzis

Guest

Why is my concrete floor sweating?

Concrete sweating usually occurs when warm air comes into contact with a cooler concrete slab and it causes the concrete floor to sweat. ... After a humid night, water vapor in the air will come into contact with the cooler concrete floor and will condense into morning dew.

Simon Sarris

Guest

How do I stop moisture in my concrete floor?

Methods Used to Stop Moisture in Concrete FloorsLow-permeance Vapor Barrier or Retarder.

A Low-permeance vapor Barrier or retarder can effectively keep below-slab moisture from reaching the flooring system.

...

Allow Natural Drying of Concrete Slab.

...

Keep Excavation Free of Water..

pl_rock

Guest

Do you need underlay on concrete floors?

Most sub-floors will be either wood or concrete. Concrete bases need an underlay with a moisture barrier, a damp proof membrane (DPM) or a separate barrier to protect the floor from damp. If the sub-floor is wooden the choice of underlay will depend on what is being laid on top.

Sam Chen

Guest

Can I cement my whole backyard?

In general, if you are doing any work which is going to modify your floor plan, then, you do need a permit. If you are going to pour concrete for a patio in your backyard, then, yes, you do need a permit.

Rohit Singh

Guest

Is a vapor barrier necessary behind cement board?

Cement board is heavy enough and breathable enough to take the moisture without a problem. By having the vapor barrier behind the cement board you stop the moisture going further into the wall. ... You should NOT place a vapor barrier BEHIND the backer board.

Daniel T.

Guest

Does cement board in shower need waterproofing?

“A waterproof membrane or vapor retarder membrane must be specified to prevent moisture intrusion and protect adjacent building materials.” ~B412 Bathtub or shower with prefabricated receptor. Cement board or Fiber-cement board. Ceramic Tile. ... Consult local building code for moisture barrier requirements.”

sleske

Guest

Do I need insulation under a concrete floor?

Creating an insulation layer and a vapor barrier between the concrete slab and the ground beneath it is the best practice in insulating basement floors.

The insulation barrier will help keep warm air in, and the vapor barrier will keep unwanted moisture out..

Benjamin Pasero

Guest

How much insulation do I need under a concrete floor?

A 50mm thick layer of proprietary floor slab insulation is usually enough to reach and maintain the target U value but this should be checked with an architect first. Insulation sheets should be laid tightly together with the joints staggered to avoid movement.

Richard Garside

Guest

Should you put a vapor barrier behind cement board?

You still need a vapor barrier with cement board, although in this case the barrier can go behind the board. Cement board is heavy enough and breathable enough to take the moisture without a problem. By having the vapor barrier behind the cement board you stop the moisture going further into the wall.

Charles Lavalard

Guest

What is the best insulation for under a concrete slab?

Applying a bead of polystyrene-compatible caulk or mastic to the top of the insulation board minimizes water infiltration behind it. 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.

Mellon

Guest

What is the purpose of a vapor barrier under concrete slab?

The use of a vapor barrier (more accurately termed a vapor retarder), having a water vapor permeance of less than 0.3 perm is frequently used to retard the flow of moisture through the slab. These vapor retarders are typically polyethylene or polyolefin sheeting materials.

Ali Irani

Guest

Do I need DPM on concrete floor?

Do I need a DPM under laminate flooring? Simply put yes. In order to prevent damp rising through the concrete floor and causing issues, a DPM should be used under all final floor types including wood flooring, laminate, vinyl and floor tiles.

instanceof me

Guest

Is concrete a Vapour barrier?

Actually, no. Air barriers need to be continuous and free from holes, but vapor barriers do not need to be. Lots of vapor moves by air movement, not a heck of a lot of vapor moves by vapor diffusion. The concrete slab is the air barrier, and the ripped and torn and punctured polyethylene sheet is the vapor barrier.

Midhilaj

Guest

Do I need concrete reinforcing mesh?

And yes, mesh is important: Concrete is strong in compression, but not under tension. So, if it flexes, like a slab with a vehicle on top of will do, it cracks at the bottom whre the flexing becomes tension. Steel mesh will prevent this to a large degree and hold it all together.

Paulo Scardine

Guest

Do I need to cut my concrete slab?

“The minimum depth of sawcut using a wet conventional saw should be the greater of at least 1/4 of the slab depth or 1 in. (25 mm). The minimum depth of sawcut using an early-entry dry-cut saw should be 1 in. ... Some slab designers require cutting the slab the following day to 1/4 of the slab depth to deepen the 1 in.

Bo Persson

Guest

Do I need to reinforce my concrete slab?

Concrete is an incredibly resilient material, which is why it's used so much in building and construction work. However, some types of concrete structure require reinforcements, which are often put in place as the mixture sets.

Johan Dettmar

Guest

Do you need a vapor barrier under concrete driveway?

The application of vapor barrier in exterior concrete is unnecessary due to the fact that water penetration does not matter. Any slab on grade that is enclosed and on the interior of a building should have a vapor barrier installed prior to pouring concrete, especially if flooring will be applied.

yatu

Guest

Do you put plastic under concrete slab?

In California they place sand between slabs and plastic vapor barriers—in Florida they don't. Almost everywhere (except “California”) that slabs are placed on the ground—a plastic sheet—a vapor barrier—is located directly under the concrete slab and on top of the ground (Photograph 1).

vcsjones

Guest

How do I remove concrete from my lawn?

Steps for Removing a Concrete SlabStep 1: Create a Void Under the Concrete. The best way to speed up concrete removal is to create a void underneath the section of slab you're working on. ... Step 2: It's Hammer Time. ... Step 3: Pull Apart and Remove the Broken Concrete. ... Step 4: Repeat Steps Until Concrete Is Demolished.Jan 16, 2019

Nathan H

Guest

How do I stop condensation in my concrete shed?

9 ways to effectively reduce garage condensationControl your garage's temperature. ... Use a vapor barrier. ... Dry your wet vehicle off after parking it in the garage. ... Check your ventilation. ... Inspect your drainage. ... Apply a floor coating. ... Install a dehumidifier. ... Get rid of that old garage fridge or freezer.More items...

FluxedScript

Guest

Do I need gravel under my concrete slab?

Whether you pour concrete for a walkway or patio, a strong gravel base is required to prevent the concrete from cracking and shifting.

Gravel is especially important in clay soil because it doesn't drain well, which results in water pooling under the concrete slab and slowly eroding the soil as it finally drains..

Rich DeBourke

Guest

Is concrete slab waterproof?

Concrete slabs are not impervious to water. In fact, given the right environmental conditions, the floor slab can transmit gallons of water into the living space as vapor, and in extreme cases, actually show ponding water. ... The pre-construction solution is to use an underslab vapor barrier.

Blender

Guest

Should I insulate plaster walls?

If your historic house has original plaster walls, you should not blow insulation into the exterior walls.

Old houses with plaster walls have no vapor barrier under the plaster to stop moist air from saturating the insulation.

Instead, plaster walls are designed to allow the free exchange of air and moisture.

Dimitre Novatchev

Guest

Should I insulate under my concrete slab?

Creating an insulation layer and a vapor barrier between the concrete slab and the ground beneath it is the best practice in insulating basement floors. The insulation barrier will help keep warm air in, and the vapor barrier will keep unwanted moisture out.

Suresh Vishnoi

Guest

Should you put plastic under concrete slab?

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: Although it may seem water-tight, this grade of material allows a lot of water vapor to pass through.