Backerboard Concrete block bench (Wetroom)

21 Jan 2017
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United Kingdom
Hi All,

Hope you can help.

I am just wondering whether I should backer-board the concrete block bench in my wet room, applying it with a tile adhesive. Or can I tile directly on top of the concrete block work?

I worry about moisture or cracks within the concrete block/to tile directly on top of it, so wondered it may be best to backer-board it then tile first to prevent this?

Also, I noticed I did my block work in front of the backer board. ideally, I should have done my bench first then backerboarded on top. So if I was going to do this with the idea of backboarding the bench then should i cutout a recess in the wall and then slide the backerboard on top of the bench but under the backer-board wall.

Photo is below.


thanks all.
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If you have gone to such effort to create a nice wetroom then don't skimp now.

Do it in the right order, cut the joints to the board's properly as per instructions, seal it appropriately and create your bench with a one of the thin boards available, you don't need a thick one since you have block backing already.

Will last ages when done properly, for only a small extra costing.

The wedi parts are adhered to the block using thinset mortar or wedi Joint Sealant. Adjoining parts are glued together using wedi Joint Sealant continuously applied along all foam edges of a board part. Excess is spread flat over the seams using a putty knife. Where the part’s backs meet the wedi wall, modified thinset mortar is used in a full contact surface bed. Once the bench is built, a final bead of wedi Joint Sealant is applied to safely seal all seams to the wedi wall. The vertical front part of the bench will show a small gap to the pitched floor. Please fill with thinset mortar and alkali resistant fiberglass mesh tape by wedi, applied over this seam.

Cover exposed blue foam board edges with wedi joint sealant or a strip of wedi Building Board so even small tiles can be adhered safely.

Take the time now to ensure your walls are flat and level, to make tiling much easier. You also need to properly prepare your penetrations and joints.
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