Plastering in my extension

[Micilin]

I probably use more butter on my sandwiches, than some skimmers use plaster on a whole wall.

Nowadays you can't take butter to work - you have to use olive oil based spreadable stuff, with omega 3 and cholesterol reducing what nots.

And no sandwiches (pieces my parents call them) - it's a wholegrain rye panini with a rocket and crayfish salad.

 

[jrplastering]

dont micilin your makein me hungry ................tell me more??

 

[stevethespreader]

Can't see why anyone would try to remove well-adhered paint. An SBR slurry would be better. If the paint is flaking then some kind of wire brush/scraper prior to SBR slurry is the way to go. I sometimes wonder if you guys live in the real world.

this is the way i was taught, painted outside wall now been brought inside because of extension tight bonding scratch coat float coat render heres one i did on job a few years ago View media item 29340 View media item 29341 View media item 29342 View media item 29344

 

[NickB_99]

this is the way i was taught, painted outside wall now been brought inside because of extension tight bonding scratch coat float coat render heres one i did on job a few years ago

Hi Steve.
What's the advantage for the tight Bonding followed by Render, instead of two Render coats? Cheers.

 

[stevethespreader]

if you used 2 coats of render you would need an sbr slurry or splatterdash, or hack the paint off, also with bonding you can float coat it the same day.

 

[roughcaster]

Ive put bonding coat onto a cement render s/coat many times Stevie, but i've never, ever, cement rendered onto a Gypsum bonding coat scratch coat. I've never seen anybody else do it that way either. I was always taught the opposite way to you,, gypsum plaster onto cement render,, not cement render onto gypsum plaster!!! I know we're talking internal work here, but putting a heavy top coat of sand and cement render, onto a thin lightweight plaster backing scratch coat, goes against all my thinking. I'm curious to see what others say about it. It works because you've done it,,, i wouldn't do it,,, but lets see the comments,,,,,,

 

[stevethespreader]

i've never, ever, cement rendered onto a Gypsum bonding coat scratch coat. I've never seen anybody else do it that way either. I was always taught the opposite way to you!!! I know we're talking internal work here.

well im shocked at that lol only the other week one our our ops plasterer rendered over bonding in the kitchen, i cant see the point of rendering first and then putting a bonding coat on top of it although render and bonding is compatable with each other, i cant beleive you havent done it //www.diynot.com/forums/viewtopic.php?t=246886&start=15

 

[stevethespreader]

just seen your edited post lol yes i suppose its going to be one of those have you or haven't you debates i know im not the only one using this method, and i don't see nothing wrong with it,

just for the record, i submitted these pics in the onsite assessment nvq folder about 3 years ago and remember when the assessor was browsing through it, and he picked it out and asked have you done a tight coat of bonding here on the painted wall ready to take render? and i said yes he didn't even question it, also i was working for a firm who asked me to do it, theres not one good reason why not

 

[roughcaster]

Let me tell you where i am on this Steve, and this is all with my deepest respect for you as a plasterer, and my friend.

To me, the appropriate background for cement render top coat, is a render scratch coat. Gypsum Bonding coat is not an appropriate background for cement render. It is not meant to be used as a scratch coat for cement render. It is a "lightweight undercoat plaster", and has very little strength for carrying any weight. Sand and cement render is very heavy. I'm surprised,,, nay,,, even shocked,, that your assessor asked whether you had put on "bonding coat first, ready to take the cement render".

I'm sure the render will stay on the wall,, but i have in the past, scratch coated and cement rendered concrete ceilings. If i had scratched them with bonding coat first, and then top coat sand/cement rendered on top of the gypsum bonding scratch coat,, the heavy downward weight of the cement render would have pulled away from the weak, lightweight plaster scratchcoat. Its the same if you're fitting expamet corner beads before rendering. You wouldn't/shouldn't use dabs of plaster to hold them in place and then render over them.

That's my view for not doing it that way,,, always will be,,,, unless,,,,,,,,,,??.
Merry Christmas Mucka.

 

[stevethespreader]

bonding sticks to painted surfaces really well and as we all know is more than compatable with render, the system works and is used, but also i apprecaite your views, also i think you are one of the most respected spreads on here and thanks for calling me a friend happy christmas to you too

 

[1john]

Just something I noticed the other day, in the other halfs fathers extension, some spread has rendered and skimmed over render and skim, it's all still up there, all bar a small peice missing from where there has been a crack coming from a removed extractor fan, which is where i noticed it.

 

[dazdel]

Roughcaster is correct, also sand and cement shrinks, gypsum expands.
With the gypsum being underneath, it can't expand, meanwhile the sand and cement is trying to shrink, both surfaces are on the move, which will lead to failure of the bond after time.

The two products are not compatable with one another, and never heard anyone doing this before, and been pushing shyte up walls for 27 years.
While the bonding may be dry and hard, the sand and cement when put on top of it will soak up the water, and so the bonding gets a good soak, to cut to the chase, bonding sets hard in, let's say a hour and half, sand and cement needs 24 hours or longer, so the bonding gets a good long soak which can break the crystal structure down and go soft, meanwhile the sand and cement is trying to cling to it. This whole method is a no no.

 

[stevethespreader]

bonding is used on render all the time chasing patching ect even rc says hes put it on render, if there not compatable theres going to be an awfull lot of walls falling down.

 

[stevethespreader]

just on another note how many here have packed rsjs out with bonding b4 rendering over them?

 

[Micilin]

This is one I've not come across before! Always have started out stronger and got weaker with each coat,

Bonding, like finish or hardwall , onto sand and cement is standard practice but sand and cement onto bonding I've never seen done, never seen on any spec and can't see anyone recommending it ( manufacturer /architect/engineer etc). I honestly can't see it being a standard practice in a City and Guilds/NVQ etc either

Now, if the bonding is well keyed, no movement , no moisture, I can't see the render coming off without being hacked off.

I would not do it on a ceiling, onto metal lathing or anything that might have movement.

If there is any chance of moisture it would be chancy as bonding will turn into mush over time unlike render.

But really , in practical terms I just don't see the need for it!! Why not just use a slurry/spritz/scud coat onto the wall and render onto that? Why faff about with bonding at all? For bonding to stick to a painted surface there must be a key, either physical or chemical - and the same criteria apply for render . With the bonding you are just introducing an unnecessary operation that may be a concern

To me it is a bit like sticking beads with finish/bonding for sand and cement render - it's done as a short cut for those who can't use sand and cement to do these things, and where there this is done outside or where there may be moisture it is very poor practice .

No reflection on you Steve, as you know - and this is probably the first thing we 've not seen things from much the same view, so interested in the application .!

I've never seen bonding used to fill catnics to be covered with sand and cement either, but on inside work I've seen the render doped with a bit of finish etc , which is a bit different. Usually a strong bit of sand and cement mix to fill out,m scratch and use render to fill if it is a render job.

I'd be interested to see any spec etc that shows this as a method ?