Rendering on to cement boards..

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KevinHarrison

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I’ve read the other thread ongoing thread for rendering onto cement board,but Seemed to get a little bit lost so I’ve started my own..

Im a plasterer but do very little Rendering,henceI’m asking for some advice/help..

The scenario..
The customer has built a garage/carport.
Mainly out of timber,it was suppose to be all cladded in timber,but building control has asked for a fire stop using cement board on the boundary wall to next door.
Now this can’t be Cladded it’s got to be rendered.
The customer wants this doing in the cheapest possible way as no one will see it
On the same token he does not want it cracking and falling off !!

So feel free to fire away some options..

1 guy has recommended taping the joints and tyroleaning straigh over the top..

when I read the other thread there was a small discussion on wether the cement boards or internal or external
I’ve not put the boards on so I don’t know what they are
Is there anyway of knowing if they are internal or external ?
 
KevinHarrison said:
I’ve read the other thread ongoing thread for rendering onto cement board,but Seemed to get a little bit lost so I’ve started my own..

Im a plasterer but do very little Rendering,henceI’m asking for some advice/help..

The scenario..
The customer has built a garage/carport.
Mainly out of timber,it was suppose to be all cladded in timber,but building control has asked for a fire stop using cement board on the boundary wall to next door.
Now this can’t be Cladded it’s got to be rendered.
The customer wants this doing in the cheapest possible way as no one will see it
On the same token he does not want it cracking and falling off !!

So feel free to fire away some options..

1 guy has recommended taping the joints and tyroleaning straigh over the top..

when I read the other thread there was a small discussion on wether the cement boards or internal or external
I’ve not put the boards on so I don’t know what they are
Is there anyway of knowing if they are internal or external ?
Click to expand...
It will usually have it printed on the board
 
More importantly are they cement boards like hardy backers or are they an actual render carrier board.
 
Get a spec from a render supplier ie Weber or who ever materials you gonna use and also talk to Knauf in terms of the aqua panel boards and installation, you can’t afford to f**k this up
If you did it will cost a bomb to put right
 
If it's Hardibacker you could mastic the joints and paint it, Snowcem or whatever it is that they paint houses with now?
 
you ask very relevant questions:

Are they looking at a Cement board lining to the structure to give a fire performance to the boundary?
Or, replace the timber cladding with a fire rated cement board cladding to the boundary side?

if looking for cement boards direct to TF structure for fire .... suggest they get advice from the timber frame supplier, TRADA or STA (structural timber association) - this needs to be a tested solution for compliance!!

if looking at cement board A1 fire rated cladding to replace the timber cladding... get in touch as Knauf Aquapanel Outdoor can do this
BBA assessed with multiple render system suppliers, so options for finishing
Would not recommend tape and joint and Tyrolean only - the min 5mm modern basecoat and mesh gives the weathertight layer and also bonded the boards to reduce risk of cracking at timber frame settles. You can then use a tyrolean or modern thin coat silicone top coat...

Knauf Aquapanel Cement Boards have several variations - the board types are printed on the smooth side of the boards.
Only used the Outdoor board for external walling applications - Outdoor is freeze thaw tested, heavier so more suitable for external loads and potential impact.... the Outdoor is also the BBA assessed one!

There will be more questions... feel free to ask them here, call me or search the forum

good luck

Richard Lord
Knauf
Rlord@knauf.co.uk
07918 766577
 
Last edited:
If the project is a new build, and subject to new build insurance, some more recently commonly used boards are now banned - refer to their insurance provider for qualification....
 
KevinHarrison said:
Really !! how do you know that ?
Click to expand...
For interior....
20200930_114611.jpg
 
I’ve spoken to the customer this morning and he says it’s printed on the boards “Render ready”
Why is this if they are for interior use ?
 
Wickes have come back to the customer
Saying these boards can be used externally

So now the question is what can be used ?
 

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Can anyone recommend a thin coat system to use
Or point me in the right direction of where to ask
I’ve never done this type of rendering before
 
Thanks @martinemj . We have both thin coat solutions and lightweight monocouche systems designed for render carrier boards.

We would need to see data and test sheets from the board manufacturer to determine if this is suitable to receive render or even if external use is permitted. Fire rating being a huge factor as well. They are many great boards on the market and there are also some that are not. Always get the data from the manufacturer, I've seen some nightmares in my time and its a costly thing to put right.
 
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