# Forum Home Renovation Rendering  render over blueboard

## malachi

hi all, can someone settle a debate between me and my dad.I have about 50 square metres of blue board to render, he tells me to use a textur coat product,which i know is the right way, but to save some cash i was going to apply some bond crete on the blueboard, then a rich mix of mud as the base coat ,then your render coat ,would this work?

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## johnc

You run the risk of cracking on the joins, go find some spec's but the acrylic coat will be nothing compared to ripping off the lot later and replacing if you get it wrong. The key to blue board is joint preparation, and if you want to go down your path you might have to bridge the joins with a suitable mesh product to allow for movement. The quality of the sand is always an issue, to much clay such as packing or brickies sand can also get you into trouble. 
John

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## vGolfer

We redid our backyard about 7 years ago...I was pretty much a novice when it came to anything handy back then, but I enclosed our yard in blue board then just rendered over it with a sand and cement mix with some bondcrete as well. It is still there all these years later...some small cracking but I am sure we would have got cracking with any other finish as well.

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## malachi

Interesting vGolfer, were there joints to prepare before you rendered ?

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## malachi

Thanks for the advice Jonn

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## pabs

> We redid our backyard about 7 years ago...I was pretty much a novice when it came to anything handy back then, but I enclosed our yard in blue board then just rendered over it with a sand and cement mix with some bondcrete as well. It is still there all these years later...some small cracking but I am sure we would have got cracking with any other finish as well.

  Hi my name is Paul, Im new at this so correct me if im not posting my question right. Like the other guys in the thread I to have put up a blueboard wall in my back yard, I used the mesh tape between joints & flushed with an acrylic based patch cement( i even added some extra cement power to stiffin up the mix) i sanded back the joint thinking it was flush, I then used a medium to coarse roll on texture paint with a medium spaggetti roller but to my horror the joint lines still can be made out.Can I fix this? What did I do wrong?( only coat of texture paint has been appllied, if that helps!?.

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## john_unitex

Hey Pabs, 
What kind of mesh did you use? I would recommend an alkaline resistant fibreglass mesh as any other will be 'eaten up' by the cement in the patch. Also, did you just do the joints with the patch, if so this could be the problem. 
First step when rendering/texturing blueboard is to mesh the joints, then use the same patch over the whole sheet. The reason for patching the whole sheet and not just the joints is because texture will absorb differently into the blueboard and patch, which can lead to colour variation and the possibility of the joints showing through.  
John

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## pabs

Thanks John, whats the best way to fix this, should i start fresh with new board, sand off the texture paint , give 2nd or 3rd coat of texture paint or some how render it. Any input would be appreiciated. 
thanks again 
Pabs

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## john_unitex

Sorry to say it, but it sounds like you'll have to start again with new boards. The problem is, if you try and go over what you have there then more problems could be created (eg, the texture you have on there could delaminate, peeling off the top layels - btw this is worst case).  
Rendering blueboard; 
Step one:
Mesh the joints with 50mm fibreglass mesh and a polymer modified render 
Step two:
Use the same polymer render over the whole surface 
Step three:
Texture over the render 
This is probably the more expensive option, as you have already purchased and used materials, but for the best look this is really the only way to go.  
Goodluck. Maybe you could get some photo's for us to see, with current wall and then when you finish.

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## pabs

Thanks again for the advise,I'll gets some photo together to show you the out come. 
thanks again 
Pabs

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## myla

hello, 
you need to get more "body" over the entire board, textured paints just aren't thick enough to cover 
unless you go for ultra course (ie. roughcast), but typically no-one wants that 
you can fix this if paint is sound, 
score wall with grinder going just into the cement sheet in criss cross patten, remove dust and clean entire wall 
this also key for render 
get bags of polymer render (around $40/bag) and trowel over and re-mesh with wider tape over joints, do as skimming entire wall (not before) and allow to dry 24hrs 
do another thin coat and float neatly, then paint or apply trowel on texture to color 
thankyou 
myla

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## pabs

Thanks for the advise, but what do you mean when you say score, thin lines with cut of wheel or a thick grinding wheel and try to lift the paint off all together. Im sorry that your talking to a "dumby" I just want to get it right this time.  
Thanks again 
pabs.

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## myla

hello, 
score the wall with a grinder ie. 4-inch with masonry flexovit blade 
just cut into the cement sheet, 1mm or so deep, diagonal graph patten, lines across the wall 
this not to take paint off, put "key" for render to stick onto board 
paint must be in good condition 
thankyou 
myla

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