thickness of render

[dave1972]

hello all.it`s my first post on this forum and was after a bit of advice.the render and pebbledash on the front of my house virtualy fell off this winter. i`ve just stripped it all back to the brick.it`s a 1930s house of red brick.while stripping the old render a lot of the bricks have split,with maybe 20 to 30mm splitting from the face.what`s left is sound but it means that i`ll need to build the render up in several coats so that i can level with the bricks that are still whole. hope it all makes sense so far! i wanted to know what mix i should use for the base coats,and is there a problem with building up too many coats of render?thanks very much for your help, dave.

 

[stevethespreader]

dub out the holes and cracks first with a 4-1 mix with waterproofer then give it a scratchcoat of 4-1 with waterproofer then your top coat

 

[jrplastering]

top coat is 5:1 by the way

 

[dave1972]

thanks very much guys.i`ll need to repoint first as the black mortar is crumbling.should i prime the lot with sbr and what ratio to water?

 

[stevethespreader]

thanks very much guys.i`ll need to repoint first as the black mortar is crumbling.should i prime the lot with sbr and what ratio to water?

if your rerendering, the bed joints should be cut or raked back by ten mil for a better key, i wouldent sbr it but someone on here may offer you different advice

 

[Micilin]

Further to above advice, which I would follow, you just need to make each coat you put on slightly weaker than the last, This doesn't have to mean mean strictly 4:1, 5:1 6:1 as you may get too weak if you need more than three coats.

If each coat is applied properly and keyed, you don't need to worry about the number of coats although if you are looking at 30mm overall (not in patches) you should consider mechanically fixed rib lath.

If you rake the joints and fill the holes( and key the repairs with a scratcher) you won't need SBR. SBR gives you a key and seals the wall up .

If you wet the wall and use a WP, then the scratch coat will seal the wall up for you

If you need either when rendering NEVER just paint SBR on. Mix it with cement/sand or just cement to make a slurry (depending on whether going onto it wet or dry) which is brushed on.

 

[dave1972]

thanks again everybody.feel more confident about it now.i`ve wire brushed and soft brushed the whole area but due to the mortar being crumbly it`s still a bit dusty,thats why i thought i should sbr it all.do you think just dampening the wall will still be ok?if i need to make a slurry,roughly what ratios of sbr/water/cement?