rendering a wet patio wall

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david29

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good evening gentlemen,

I've got a job rendering a raised patio (concrete blocks with rebar) for a friend (1.2m) it has been rendered in the past and the guy done a awful job! He has rendered straight on to green paint, which looks like some kind of gloss so therefore it is all coming away.
I have now stripped the old render off the wall and realised there is a lot of wetness trying to come through the wall I think this may of caused the failure of the old stuff with freeze thaw etc?

Ok so my plan was to....

  • Cut some criss crosses with the angle grinder to provide a better key.


  • Drill some holes at the base of the wall and poke some tubing through, should i mix up a sbr/cement slurry to seal the damp wall before I do the scratch, I am worried if I go straight on it'll come away again in the future!


  • Scratch 4sand-1lime-1cement with waterproofer. 8-10mm


  • Finish with 4.5 sand-1lime-1cement with waterproofer and maybe a splash of sbr? 6-8mm


  • What is the best thing to do at ground level I was gonna use a stop bead just above ground level (lawn) as I thought the render may blow over time if it goes into the ground?


Sorry if I sound like an idiot Im not a proper spread I just do bits and pieces for friends and family, so I like to make sure I get it right:RpS_thumbup:

Any help would be amazing:RpS_biggrin:

Cheers guys
 
Oh forgive me I'm with you now, you mean blackjack
Is that ok to render over?
Should I chuck some sharp sand at it while it's still tacky for a key?

Many thanks for your help :-)
 
Black jack ! Henry i,ve not heard anyone say that for many years .the more resent chemical tanking systems are cement based (s&c will bond to them ) we use Vandex BB75 with SWS bondaid plus ( safe guard ) have a look online ,hope that helps
 
lol I'm obviously well out of touch:RpS_blushing:

Thanks so much Keith I really appriciate the help, my god I never thought rendering a patio wall would be so complex!!

I've just read the data sheet on the vandex it seems I will have to get the green paint off the wall as it says to go straight on to the masonary background any thoughts??

what is sws is it a modern sbr? is it to reduce chances of cracks? do you add it to all coats? do you still use waterproofer with this system?

do i need to soak the wall first?

and finally is there any tricks with the vandex application does it need scratching etc or do I just throw a tight coat on and wait for it to set ??

Im so sorry for all the questions I wish I didn't agree to do the bloody thing now. Where do you live keith want a job i'll knock up for ya:RpS_thumbsup:
 
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