Question - Can you put cement board on concrete?

Answered by: Cynthia Davis  |  Category: General  |  Last Updated: 07-09-2021  |  Views: 1177  |  Total Questions: 11

Normally, installing cement board is not regarded as necessary when you are laying tile onto a concrete slab since this subfloor is already cementitious—adding cement board would be redundant. The concrete has been painted over, and paint is not an acceptable surface for thin-set adhesive or mortar. Use a notched trowel to spread the thin-set on the concrete where your first sheet of cement board will be placed. Use the flat side of the trowel to spread the mortar firmly against the concrete to achieve a good bond, and then rake back across it with the notched side to leave ridges in the mortar. Cement board is used for most floor tile and has all but replaced plywood and drywall backer materials for wall-tile applications in wet areas, like showers and tub surrounds. Ceramic tile laid over cement board is one of the most durable floor or wall surfaces you can install. It can be used on the exterior of buildings as a base for exterior plaster (stucco) systems and sometimes as the finish system itself. Cement board adds impact resistance and strength to the wall surface as compared to water resistant gypsum boards. Floors. Both 1/4- and1/2-inch cement board are appropriate for floors. To install cement board on floors, cement board manufacturers mandate a 5/8-inch plywood subfloor or OSB underlayment. They also require a 3/4-inch subfloor where tile size exceeds 12 inches.

https://www.homeownershub.com/maintenance/under-the-bathtub-durock-or-just-subfloor-317947-.htm

There's no real reason to have the cement backer board under the typical tub. I usually just run it under the front edge a couple or three inches so the tub is resting on it, and the rest of the tub is supported by the wood blocking attached to the studs.

https://www.thegroutstore.com/blogs/news/88486593-new-mortar-doesnt-bond-to-old-concrete-read-this

Concrete, mortar or similar materials are not designed to stick or bond to old surfaces. You will not get any satisfactory results if you simply add new mortar to old. It just doesn't work. Using a modified thinset mortar would be the preferred method for this type of installation.

In general, 1 1/2-inch galvanized nails will hold the board firmly in place. For flooring or wall installation, some builders choose to apply a thin layer of thinset mortar under the cement board to prevent any shifting or expansion. Even if you use this extra adhesive, you should still apply the nails or screws.

https://homeadditionplus.com/dev/tiling-floors-walls/how-to-attach-cement-board-to-brick-wall/

Use a hammer drill to pre-drill the holes in the mortar and make sure you use Tapcon anchors that penetrate into the mortar at least 1. 5 inches. Once the furring strips and liquid nails adhesive has set up for 24 hours, then attach the cement board to the furring strips using non-corrosive screws (Rock-on fasteners).

https://www.thespruce.com/can-you-install-tile-directly-on-concrete-1822600

While you can install tile directly on concrete, problems erupt when the concrete cracks or shifts. All of the movement in concrete is transferred to the tile. Cracks in concrete immediately become cracks in the tile.

https://www.doityourself.com/stry/5-reasons-to-use-a-vapor-barrier-in-your-shower

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.

https://www.bobvila.com/posts/93465-hardibacker

cement backer board is not waterproof, but water cant hurt it, even when soaked in water for months or even years

https://www.familyhandyman.com/tiling/tile-installation/cement-board-ceramic-tile/

Cement board has a smooth side and a rough side. Face the rough side out if you will be using thin-set mortar adhesive to install the tile but the smooth side out if you will be using latex mastic.

https://www.usg.com/content/usgcom/en/resource-center/faqs/563.html

Can USG Durock® Brand Cement Boards be used on the interior and exterior of buildings? Yes. They can also be used in below-grade applications such as basements. Below grade in this application does not include direct ground-contact applications.

https://www.thespruce.com/cement-backer-board-1821658

Cement backer board is mainly used as a sub-surface for tiling. Cement backer board is often used as a tile base on plywood or OSB subfloor. Cement backer board on concrete as a subfloor or underlayment is usually not recommended or needed. In most cases, you can apply tile directly to the concrete.

The USG DUROCK Waterproofing Membrane is a pliable sheet-applied waterproof membrane and vapor retarder for use with USG DUROCK Brand Shower System. It also has an extremely low permeability rating, making it ideal for wet areas, including continuous-use steam showers.