Backer Board. Use Washers?

[SteUK]

Hi all,

Going to be fixing 'no more ply' backer board to a mixture of wall substrates (both breezeblock, one with old sand and cement render, the others the same but with a plaster finish skim). Will be solid bedding (8mm square notched trowel) with mapei keraflex maxi, and mechanically fixing with 55mm x 5mm stainless steel screws into Fischer 50mm universal plugs (internal breezeblock is only 50mm thick!).

Question is...should I be using stainless steel washers as well? The screw heads are approx 3mm deep and 10mm in diameter so not much wiggle room depth-wise on 6mm thick boards!

Thanks!

 

[Just Rizzle]

did a job earlier in the year the builder prepped the walls with that stuff I personally think its rubbish told him so he said it was ok to use . I tried to get him to sign a disclaimer he wouldn't next day was covering it with hardy backer board.
after watching a shulter demo on Monday would highly recommend there products befor any other manufacturer

 

[Dave]

To answer your question , yes use wedi type washers to prevent pull on screw heads.

Have you used the boards for weight issues ?

 

[SteUK]

Hmm, kind of. Few things really...

Walls are a bit up and down, 3mm maybe a few more in patches. Boards will help me get a decent flat surface to enable the best tiled finish I can achieve.

A sqm of the tiles comes on at 16kg. So with adhesive and grout, it touch and go making the 20kg/sqm for finish plaster that is on half the wall area. Factor in the finish plaster is ok suspect condition (gonna hack off the blown parts prior to fixing the boards). I am possibly too paranoid about tiles falling on my 15 month old daughter. So, yeah, boarding for that reason as well.

Around the bath (and pumped shower) I think the boards make good sense...along with tanking them naturally.

 

[Dave]

Ah I remember your other thread .. Your using the thinner boards because tight on space for thickness .

 

[SteUK]

That's me

 

[SteUK]

Don't suppose anyone with a washer in hand could measure the countersink part to see if they take screws with head diameter 10mm and depth 3mm ?