Sealing Hardiebacker Cement Board.

[Simmo1111]

Hi everyone,

I'm just in the process of building a shower enclosure in my house. I've used 12mm Hardiebacker board to line the walls and have left a 3mm gap in between the sheets as per recommendations. I'm now at the point where I need to seal the boards. I've bought the alkaline resistant tape for the joints and will buy the Thinset Adhesive to 'mud' the joints as per the instructions. I also have an Aquadry tanking kit which I ordered as a 'belt and braces' addition.

My question is..

Should I tape and 'mud' the joints between the boards with the alkaline resistant tape and then use the adhesive backed tape from the tanking kit on the top of that or is it good enough to skip the alkaline resistant tape and simply use the Aquaseal adhesive backed tape on all joints after filling them with Thinset and smoothing over. I'm wondering if the alkaline resistant tape will hinder the effectiveness of the Aquadry tape and create a surface which is unsuitable for the Aquadry tape to seal on.

Any advice would be very welcome.

Thanks very much.

Dave.

 

[Sin_Chase]

I've done exactly the same as you recently, do it all - can't be too safe in a wet environment and the tanking kit strips stick like poo to a blanket. The thinset wont hinder them, use a roller (often included in kits) to make sure they are all stuck to the wall fully.

Install boards
Run adhesive alkaline resistant tape along joints and in/on corners
Float cementious adhesives across all tape/joins

Run the self adhesive tanking kit tape along all joins, internal corners and perimeter
Paint the wet tanking kit membrane (I did 3 coats).

Little tip - When floating the thinset on the joins/tape it will dry VERY FAST. The boards suck out the moisture and it is such a thin layer you have very little time to work with. I would suggest doing a join at a time and getting it all nice and level before you move onto another!

 

[Simmo1111]

Thanks very much Sin_Chase. Pics are a great help too, thanks for taking the time to do them.