Render or texture paint on cement board cladding?

[philcvk]

Hi - I'm doing an extension in timber frame and on the outside of the studs I have OSB, breathable membrane (roofing felt), battens and cement render carrier boards. 

 

The final look I need is white render to tie into the rest of the house. The quotes to do the render (thin coat or 6mm silicon) are ££££, and so wondered if it'd be cheaper do beading with 200mm of filler around the edges and then prime and paint everything, using a good grade exterior paint? (probably exterior caulk the joints of the cement boards too).

 

I'd be really interested to hear what others have done on render carrier / cement boards for the final layer. 

 

I've heard issues with thin coat render peeling off the cement boards, and nervous about the paint option that this could be one cheap fix not to make. Would be great to know what other people have done, thanks

Edited 13 hours ago by philcvk

[nod]

Unfortunately paint and filler won’t stay on cement board 

Thin coat is fine if it’s done right 

[Nick Laslett]

9 hours ago, nod said:

Unfortunately paint and filler won’t stay on cement board 

Thin coat is fine if it’s done right 

@nod are you sure about this? All my soffits/undercloaking is cement board. It has been up for 2 years, paint seems okay. I’m pretty sure I just followed M.I. on how to paint; use SBR primer. Of course this use case is completely different to what the original post is asking. 
 

https://www.sts-board.com/wp-content/uploads/2024/05/STS-Construction-Board-Product-Leaflet_2024.pdf

 

@Adam2 did you go ahead with painted cement board as you suggested in this thread?

 

 

Edited 1 hour ago by Nick Laslett

[saveasteading]

10 hours ago, nod said:

Unfortunately paint and filler won’t stay on cement board 

There are systems where a netting is applied first, with screw fixings, then the render sticks to the board enough, with the additional support of the mesh. 

Very expensive but it works and I would not advise any other way.

 

Or apply sods law and spill paint or render on it accidentally, as we know that doesn't come off.

[nod]

Think coat render 

we do lots of TF buildings that way 

Sticks like sh## to a shovel