What to apply to brick to waterproof, before plastering?

Discussion in 'Builders' Talk' started by OddJobBob, Mar 26, 2014.

  1. OddJobBob

    OddJobBob New Member

    Hi guys, my first post, easy question.

    I need to redo a small section of render at the front of the house. What should I apply to the brickwork to waterproof it? Once that dries, I can then apply 2 coats of render (scratch + 2nd coat).

    One idea was maybe to do a slurry of waterproofer and render and paint in on with a brush and once that becomes tacky, to add the 1st coat / scratch coat?

    Not sure what product to use though for waterproofing purpose, pls advise!

    Cheers.

    Bob
     
  2. Sean_ork

    Sean_ork Screwfix Select

    nothing
     
  3. OddJobBob

    OddJobBob New Member

    Hi Sean, thing is, the plaster section I am redoing is a small strip which runs along the bottom, next to the ground. Photo below shows what I need to replaster. I want to waterproof so that there are no issues with rain / water, even though the patio is angled away from the house for water run-off.
     

    Attached Files:

  4. Sean_ork

    Sean_ork Screwfix Select

    nice flags, where is the damp proof course in relation to the top of them ?
     
  5. OddJobBob

    OddJobBob New Member

    Hi chap, the property was built in about 1840. Surveyor thinks there's no DPC. I challenged him and suggested there might be a slate DPC but he doubted it, as slate DPCs came in later than 1840s he says and, even if there was a slate DPC, he said they're not very effective as the slate gets crushed once all the stuff gets piled up on top of it. His words not mine.

    I appreciate that usually you shouldn't go below a DPC and instead bead it off, BUT, in this case I don't think there is a DPC and hence I wanna apply something to the brickwork first, before applying any render there.

    :)
     
  6. Sean_ork

    Sean_ork Screwfix Select

    there's plenty of recipes online for waterproof render, which I'll not repeat - but I suspect you have created a problem for the future as you'll have trapped any moisture that does rise from the founds - perhaps hack off a meter of what I suspect is cement based render and replace with some that breaths such as Parmurex, combined with a injected DPC

    probably not the answer you wanted but simply filling that gap to make it look right is far from ideal - but stand by for plenty of contradictory advice from others ;)
     
    FatHands likes this.
  7. Phil the Paver

    Phil the Paver Screwfix Select

    Sean is right about injecting a DPC, if you do not have one at the moment it wouldn't matter that you have a waterproof render, any moisture in the ground will be sucked up by the bricks behind the render, in fact if this did happen and you have a waterproof render you will end up causing yourself more problems because the moisture will be trapped behind the render with only one place to go, inwards and you don't what that.
     
    FatHands likes this.
  8. OddJobBob

    OddJobBob New Member

    Understand exactly what you're saying, but here's a pic of the horrid old patio where it can be seen that the plaster goes right to the bottom. :-/ That old patio was there for a good 10 yrs...

    I'm a bit lost as to what to do really, lol. My inital idea was to render the small strip and then paint with masonry paint as that is what was done previously and it is a reasonably small / easy DIY job to do, whereas your suggestion will require me hiring somebody, which I can't really afford to do.

    :(

    Dilemma...
     

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  9. Phil the Paver

    Phil the Paver Screwfix Select

    Question is, why was the render cut off if it was ok, or had it cracked and become loose due to damp??.
     
  10. Sean_ork

    Sean_ork Screwfix Select

    looks like it was level to the top of the old flags
     
  11. Phil the Paver

    Phil the Paver Screwfix Select


    I did think that, it would be nice to know the where DPC should be, it may already be covered by render, this little courtyard looks to be well protected from the elements so shouldn't suffer from wind driven rain against the wall.

    Mixing a waterproofer into the mix and rendering that little strip may be ok, but and it's a big but, if it isn't and draws water in, we have warned you that may happen.
     
  12. Sean_ork

    Sean_ork Screwfix Select

    the considered conclusion is thus .......

    make it look nice and move before the Winter sets in
     
  13. OddJobBob

    OddJobBob New Member

    Thanks guys. I intend to have a crack at it this weekend if I can get all the bits in time. :) I understand the warnings and am greatful for the feedback.

    The old render was level to the old patio, it is a possibility that the old stuff is hiding the DPC but I cannot see a DPC at the back of the house either so... :(

    One last question. Which type of admix do I buy? There's Everbuild SBR Bond 503, Cementone SBR, Everbuild Evermix 3 in 1, Cementone Integral Waterproofer and so on.

    Which is the one to use here to add to the sand:cement mix please?
     
  14. Phil the Paver

    Phil the Paver Screwfix Select

    any waterproofer will do, no need for a all singing all dancing one, which ever one easiest to get hold of.:)
     
  15. OddJobBob

    OddJobBob New Member

    Thanks Phil. Cementone SBR seems the most easily available and is a mix of waterproof and bonding agent by the looks of things, so I will use that. I'll do pics and report back, thanks folks.
     
  16. Sean_ork

    Sean_ork Screwfix Select

    the cheapest smallest quantity will do
     
  17. OddJobBob

    OddJobBob New Member

    Thanks Sean. The Cementone SBR stuff comes as a 2.5 litre as he smallest quantity, I'll use that then. :)
     
  18. I use bitumen paint to seal the wall :)

    plasterer doncaster
     

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