Woody2Shoes":36i2yxhi said:
I'm not sure this is good advice as the OP is clearly a DIY-er - both of those methods are incredibly harsh for the substrate (brick) - They also each require care and skill to use effectively without doing more damage than good, something a novice DIY-er just doesn't have.
The wall might be being rendered over, but that's not a good enough reason to leave the brick wall scarred like Freddy Kruger! Not to mention he'll need to use a proper air fed mask if he wants to retain any semblance of future lung usage, the fine particles that come from using a concrete grinder on brick are finer than flour (so fine I've lost sight of a person standing the other side of a door just 5 feet away - I could barely make out the door.) and even a PP3 mask won't help you unless it seals ABSOLUTELY air tight around the nose and mouth.
Woody2Shoes":36i2yxhi said:
2) remove loose paint and then ignore the rest - simply attach EML to the wall with washers and screws, then render directly onto that e.g. this sort of idea:
https://ecohomecentre.blogspot.com/2014 ... -lime.html
Sorry, don't agree - see below
I also have to question that particular page, because unless that blog points out somewhere that any cracks from suspected house movement (mentioned in the article) have been treated with helibar stitches to stabilize said cracks, then the EML + lime render isn't going to do jack, and can be misleading advice when read "as is".
I mention that in case the OP's wall has any cracks, that is leading to the decision to render it.
Trevanion":36i2yxhi said:
I saw a house the other day where they were taking off the dashing back to the bare, original stone walls. It amazed me at the time because the whole house was covered in steel render mesh underneath the render, held on with red plugs and screws everywhere. This must've cost a small fortune to do at the time (Back in the 90s) with all the hundreds of metres of mesh, thousands of plugs and screws on top of the labour of drilling all those holes, hammering the plugs in and screwing the stuff on. It was truly astounding, there must've been at least 20 screws in a 500mm x 500mm square.
The main reason they were taking the dashing off? It had separated from the wall itself and had created a small hollow cavity between the wall and the render, there was a very hollow sound if you knocked on it. The render was coming off in sheets with the mesh.
I realise this doesn't actually help you at all but I thought it was interesting. In an attempt to be helpful have you tried something like a blowtorch on it to see if it softens the paint at all?
If the wall is just a garden wall then yes EML will make the render stick, to the EML, but crucially
separate from the wall - how long it will last though is anyones guess - you can make it last longer with good maintenance of any cracks and regular recoats of a good quality exterior paint, but if you plan to be there longer than 8 - 10 years, consider the option below.
If this is a house wall - read on:
Heed Trevanion's post; I recently had reason to remove a long section of render that had been attached to the wall by EML - why? It had detached from the wall, because the EML had been attached OVER PAINT and was actually forcing the water BEHIND it and into the house, causing real internal problems - so much so a large section of interior wall will have to be hacked back and replastered. It's quite likely it had been doing this within a couple of winters of being done. The EML and render came away easily in one whole piece.
The EML will hold it, sure, but the moment you get a cavity or void, there will be nothing stopping water getting behind it pretty much down the entire wall.
Scoring, or, my advice would be to rake out half an inch of the mortar bed instead,
over the entire section to be rendered, would help the render attach to the wall itself through the EML,
as long as it had been applied with enough pressure to force it into the score lines / mortar beds (and you'll never know if it has or has not), but you'll still have a bridging issue - the render can still separate from the wall as it's only physically bonded to the wall where the scores / mortar beds are (render won't properly bond to paint no matter what you try), still allowing the possibility (probability) of water penetrating behind where the paint is, and then freeze, blowing an area around it off, creating a cascade effect - I suspect that's what happened in Travanions example.
As I said, if this is a house wall, my advice would be dry sandblasting or water blasting with media (messier but no dust for neighbours, and not requiring an air fed mask), get back to bare brick, render directly onto the brick, NO EML!! regardless of what the bloke says, or how much easier it is for him and do it right - ONCE.
Render applied correctly (right, prep, right mix, properly bonded to brick etc) can easily last 100 years.
You can even water blast with media yourself, sand usually but can be Bicarb of Soda if the bricks are older and have a protective glaze on them that sand would strip off, but I would still take advice before doing it.
HTH.
