BONDING THICKNESS

[Micilin]

How much bonding do you think is the max you can put on to a pva pvabonding slurry or bondit etc wall/ceiling.

I don't think I'd like more than 10-12 mm at most on to pva, at least not in a large area .but probably more onto slurry or bond it.

 

[roughcaster]

I think you would get away with a good bit more than 10 to 12 mm thickness of bonding, especially onto a dried out slurried/bondit surface, simply because OF the rougher dried out surface. If it was onto a smoother surface, especially a ceiling, even though it had been PVA'd, i think you'd worry that the weight of the plaster might break the bond, and drop. When you think about it,, a coat of Bonding plaster, (lightweight) is at it's heaviest when it's just been put on. By the time it's dried out, there's no weight to it at all,, unlike a coat of render. I would never push my luck, and keep putting on a coat, thicker and thicker, but you get that gut feeling that all is well. I would obviously put more thickness onto a wall than a ceiling. I wouldn't normally use that sort of thickness anyway, but now and again, i'd come close to it if i needed too. Touch wood,,, i've never had any fall down/come away.

 

[trowelmonkey1]

i would be wary of putting anymore than 12mm onto a background with almost no suction, only gotta go that mill or two too thick and its slumptastic!

bow to RC's superior bonding knowledge though

 

[roughcaster]

Adding on from my last post,, there's one area, when skimming onto a slurried "solid wall", where i pay a lot of attention to prep, and that's above radiators or where wall heaters will go. Before i slurry above any of these, i'll chip the wall/plaster with claw of a hammer,, literally hundreds of times, about 2 or 3 feet above and around the rad', to give a good mechanical key, then i'll slurry, then i'll bonding coat/skim. I do that because the heat "can" cause the slurry coating to come away from the substrate, and the bonding/skim will sound hollow around the rads etc.

 

[trowelmonkey1]

tiptastic RC!!

 

[roughcaster]

i would be wary of putting anymore than 12mm onto a background with almost no suction, only gotta go that mill or two too thick and its slumptastic!

I wouldn't put all that on in one coat anyway TM. Don't forget, the wall or ceiling has been slurried and it's dried out, so you have a good grip to start with. Put on a good coat of bonding first, give it a scratch if need be, and let it steady up a "good while", then the suction from the first coat will help no end, with building out the next coat. Do you remember when i spoke to you on the phone a fortnight ago, i said that i was working on a downstairs lobby ceiling, using 13mm stop beading around the edges, well i built that thickness down with no problem at all,, in a couple of coats,, and that was onto a new, but slurried, plasterboard ceiling,, and as i said in the other reply, by the time it's dried out, there's very little weight in the plaster on the ceiling. I've not had a phonecall from that customer yet about a plastering disaster,, and to be honest, i'm not expecting one.

 

[roy c]

If you want to get a good thickness with bonding put a good scoop of cement in with the mix, a lot of people will frown on this but it has worked for me for years....

 

[roughcaster]

If you want to get a good thickness with bonding put a good scoop of cement in with the mix, a lot of people will frown on this but it has worked for me for years....

Roy,,, you're fired!!!! Yep, that's an old trick,, and it works the other way too,, put a drop of plaster into render, it tightens that up as well. Plastering cheats we are.

 

[Alastairreid]

If you want to get a good thickness with bonding put a good scoop of cement in with the mix, a lot of people will frown on this but it has worked for me for years....

do it regular

 

[roughcaster]

If you want to get a good thickness with bonding put a good scoop of cement in with the mix, a lot of people will frown on this but it has worked for me for years....

do it regular

I've read about you as well Alastair.

 

[roy c]

If you want to get a good thickness with bonding put a good scoop of cement in with the mix, a lot of people will frown on this but it has worked for me for years....

Roy,,, you're fired!!!! Yep, that's an old trick,, and it works the other way too,, put a drop of plaster into render, it tightens that up as well. Plastering cheats we are.

Same as thee olde cement in the plaster mix as well RC. All three have a place in the trade if used knowingly

 

[trowelmonkey1]

we stuck some cement into bonding only yesterday to get a curve made in a ceiling so we could get onto it with finish quite quickly, worked a treat!

plaster into render i've never considered but will park that one!

 

[Micilin]

A i'll chip the wall/plaster with claw of a hammer,, literally hundreds of times, about 2 or 3 feet above and around the rad', to give a good mechanical key,

We call that "sparrowpecking", (use a tacking/lathing hammer as well) I generally do that whenever going over old work, reskims etc

 

[roy c]

I was working on this job a few years ago and all the walls had to be plumb and straight. So I used the three dot method (top middle and bottom) and I put finish in the mix and set my dots on and put a piece of 3" lath in each dot and strung it through across the wall and when I had got all the dots across the wall and down it ,I filled in between each set of dots with the finish mix to final float finish and devilled them up. I hasten to add these walls were over 9' high and all stone and it was out of plumb in places by up to 2" from top to bottom. By putting these "Quick" drying screeds up helped by giving me something to work off. when all the wall was finally floated I removed the laths and filled in the gaps..The plaster in the mix makes it feel like a lime mix, but I wouldn't use it in the mix for spreading large areas....

 

[roughcaster]

plaster into render

This particular one you would not use in the actual rendering on the wall. I have in the past fitted Expamet corner beading for rendering internally. To set the beads in place, dabs of render would be placed in 4 or 5 spots down the corner of the bricks/blocks. The render used for dabbing the beads on with, would have an amount of plaster in the mix, to allow you to bed and plumb the beading, knowing it would be held firmly in a short space of time, because the render would "set" quickly. You "cannot/shouldn't" put corner beads on for rendering, using dabs of plaster,, it has to be dabs of render. You could also use doctored up cement/render (if pushed for time) if you were filling up a deep holes/ gaps etc in brickwork. You wouldn't do this at all in the actual cement rendering itself.