Dot and Dab cement board (hardie)

LankyPaddy · 6 Mar 2011

I'm fixing hardi-board to brick walls and am going for the DnD with through fixings method.

What do I use to DnD though?
- standard board adhesive (Gyproc dri-wall)
- rapid set tile adhesive
- something else?

jrplastering · 7 Mar 2011

drywall addy mate

headworx · 9 Mar 2011

Just done my 1st 'go' at this, Attached Sounsdhield board to a bedroom wall (down to brick).
Hard wire brushed the wall 1st, then PVA'a and left for a day or so to dry.

Used The Gtec Plasterboard adhesive, applied all round the perimeter of the board (for fire regs I think), then used a trowel to 'flick' the adhesive onto the board appporx 12" apart, maiking sure it's still quite thick on.

Placed board to wall, placed a bit of floorboard to hold off floor, then give a good whack with a length of 3x2" wood to get it to the wall better (use the flat part, a good whack doesn't hurt it). Then made sure level with spirit level.

Leant some timber to hold it to the wall and job done.

Learnt this off this site so thanks peeps, just putting the info back in.

LankyPaddy · 18 Mar 2011

First wall is on...

How long should I leave the adhesive to dry before drilling the holes for the through fixings?

jrplastering · 18 Mar 2011

couple of hours mate just make sure its gone hard first though other wise youll pull the board out of straight and true

LankyPaddy · 18 Mar 2011

Cheers, I've stuck an off cut to the wall downstairs as my test piece so I should know when it's hard.

I'll leave it until 4.

spc · 1 Apr 2011

ive tried sticking hardiebacker board on with dry wall adhesive, it failed with any vibration or knocks. have you tried patching a boarded wall into it? it crazes like hell, and with a tap of a hammer, shells off. maybe it was a one off? the only thing i could suggest is to green the back of the board or drill and plug it.

silicone the joints and scrim them before tiling also

LankyPaddy · 1 Apr 2011

The Dot and Dabs are only there to level the boards and hold them there long enough to through fix them.

I've DnD'd the whole room now, and through fixed at ~250mm centres with 80mm through fixings - a total of ~200 fixings and about a day and a half hammer drilling!

I only had 1 dab fail and the board ping out from the wall (it was slightly warped), but that was fixed with the through fixing.

All the joints were skimmed with tile adhesive, taped with fiber glass tape then skimmed again with tile adhesive. This was the technique described in the hardibacker install manual.

1john · 1 Apr 2011

Sounds like you done a sterling job

spc · 1 Apr 2011

1john said:
Sounds like you done a sterling job

agree

LankyPaddy · 2 Apr 2011

Some quick pics of the room in it's current state. Next job is to build the boxing for the soil pipe and at the end of the bath.

It's easier to make out the through fixings in the last pic. Each 1200x800 board had 5x3 fixings in it

Richard C · 2 Apr 2011

Looking good LP; avoid (as far as possible) the tile grout lines coinciding with the board joints when you come to tile.

Not sure if I've said it to you before but make sure you use quality trade tiling materials suitable for the tiles not cheapo DIY crap.

LankyPaddy · 2 Apr 2011

I'll do my best with the tile lines, using 300x600 tiles should reduce the number of grout lines anyway!

80Kg of BAL SPF is sitting downstairs

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Dot and Dab cement board (hardie)

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