Plastering in my extension

[dazdel]

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

Never seen a rsj packed out in bonding, they are nogged out by a chippie, then a peice of plaster board is fixed to it, or I nog the rsj myself.

 

[stevethespreader]

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

i know that m8 i knew this was going to cause contreversy when i posted it but theres no going back now, ive been spreading for coming up to 7 years now i was working for this firm as an improver about 4 years ago to get some render under my belt and was following instructions which is why in my first post i said this is the way i was taught,
anyway, thats what happened and to tell the truth i still dont think theres much wrong with it to this day and i think i would do it again the job turned out really good, the wall was pvade b4 the bonding went on, and have since heard of others doing it, as for the bonding in the rsj thats where i learnt that as well and i know for a fact others do it and is common practice i dont think you will find it in a spec sheet just as you wont find multi mixed with render in a spec sheet, the boys i was working with at the time were very good to tell the truth i havent come across better than them and ive worked with a few now,and the nvq story well, idident even know that assessor he just took £550 of my money and my evidence of site work and 2 months later you get a cerificate "its all about money" anyway as i say he picked the picture of the job out and knew exactly what it was so hes heard of it to, i know its new to you and you wouldent do it but would i ? yes i would as having done so already i know it works,hope everyones havin a good holiday im off now for a few drinks its my kids 5th birthday

 

[roughcaster]

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.

even rc says hes put it on render

As i said earlier, I've put bonding onto render/scratch many times, with no problems expected,,,,, ever,,,,, but i would NEVER, EVER put cement/render onto "ANY" Gypsum plaster

Gypsum Plasters,, Bonding etc, onto new or old Sand and Cement render IS COMPATIBLE!!!,, although prep will be needed for older/smooth painted render.

But beware,,

Sand and Cement, either scratch or render coats, onto ""any"" Gypsum Plaster is NOT COMPATIBLE,, and is NOT recommended. Even looking at the pics of it,, i cringe, cos it doesn't look right,, I couldn't guarantee any job doing it that way either,, sorry Steve.

 

[chipdouglas]

i have put bonding on painted walls quite a few times followed by render not much can go wrong as long as the wall is not the inside of an outside wall in exact the same situation as steve the spread, also hes right with the bonding (packing out the rsjs)

 

[NickB_99]

It's a while since I've seen a good debate on the forum - nice one guys

The BG data sheet has some info on use of Bonding on concrete backgrounds (http://www.british-gypsum.com/PDF/DS-101-01 Thistle Bonding Coat.pdf, p3, Background preparation), but I couldn't see anything for guidance on application the other way round.
I'd have pasted the text for the relevant section, but the clipboard is disabled viewing these PDFs.

 

[plstering]

iv plasterd over renderd ofers bonding and if bonded over render
as long as your primer is ok what dif dos it make ither way you look at it theres gypsom on render or render over gypsom as lon as its on the wall and it stays there looks good and paints ok who give a F**K
some spreads i know say never use PVA out side for rendering ****** i use it on rendering 99.9% of the time
lay off yer you do it your way and me and steve will do it our way OK

 

[stevethespreader]

As i said earlier, I've put bonding onto render/scratch many times,Sand and Cement,

why would you put a bonding float coat onto render scratch ?why not follow through and put float coat of render on? when ever ive done a render scratch ive always followed through with a render float coat

 

[dazdel]

As i said earlier, I've put bonding onto render/scratch many times,Sand and Cement,

why would you put a bonding float coat onto render scratch ?why not follow through and put float coat of render on? when ever ive done a render scratch ive always followed through with a render float coa t

Bonding is designed to go over THE TOP OF MANY BACKGROUNDS, sand and cement is not designed to go over gypsum plasters as you did. You fail to listen my friend. Years ago you would give a wall a scratch coat of bonding then top it with browning, however plasterers soon caught on that you could lay it on and rule it off, rub it up, then skim it, thus saving time by not using the browning over the top. You don't see much browning these days, as it's all hardwall.

 

[roughcaster]

iv plasterd over renderd ofers bonding and if bonded over render
as long as your primer is ok what dif dos it make ither way you look at it theres gypsom on render or render over gypsom as lon as its on the wall and it stays there looks good and paints ok who give a F**K
some spreads i know say never use PVA out side for rendering **** i use it on rendering 99.9% of the time
lay off yer you do it your way and me and steve will do it our way OK

Yeahh,,, whetever!!!!!!! If this all you can come up with in the debate, you said enough!!

 

[roughcaster]

As i said earlier, I've put bonding onto render/scratch many times,Sand and Cement,

why would you put a bonding float coat onto render scratch ?why not follow through and put float coat of render on? when ever ive done a render scratch ive always followed through with a render float coat

Well Stevie,, just because a wall/s, chimney breast, patched areas etc has been cement scratch coated, it doesn't mean it has to be top coat rendered. It might have been cement scratched for a reason,,, efflorescence/salts, possible damp, high suction, etc, etc, but it might also be in a room/s where the walls have gypsum plaster backing and not render. That's the beauty of a cement scratch, it's compatible,, you can put anything on top of it, unlike gypsum plasters.
I sent an e-mail to British Gypsum on this subject, to get their official verdict. I'll tell you what they say.

 

[roughcaster]

sorry double post trying to quote and ended up with 2 copies

No problem Stevie,,, just keep it 'till the next debate.

 

[stevethespreader]

As i said earlier, I've put bonding onto render/scratch many times,Sand and Cement,

why would you put a bonding float coat onto render scratch ?why not follow through and put float coat of render on? when ever ive done a render scratch ive always followed through with a render float coat

Bonding is designed to go over THE TOP OF MANY BACKGROUNDS, sand and cement is not designed to go over gypsum plasters as you did. You fail to listen my friend. Years ago you would give a wall a scratch coat of bonding then top it with browning, however plasterers soon caught on that you could lay it on and rule it off, rub it up, then skim it, thus saving time by not using the browning over the top. You don't see much browning these days, as it's all hardwall.

nothing wrong with my ears m8 or my eyes for that matter its there for everyone to see you said bonding is not compatable with render full stop,i dont know why your bringing browning into the debate it wasent even mentioned, for the record i know everything about every undercoat and top coat you could mention, all the work u done back then with the bonding is all being chopped out cause its either black and crumbling with damp and we are now replacing it with fresh render you have created lots of work for us cheers for that much appreciated

 

[stevethespreader]

I sent an e-mail to British Gypsum on this subject, to get their official verdict. I'll tell you what they say.

lol ok m8 you do that but you cant really take what they say as gospel i asked them about a bathroom once,and if they had there way sand and cement would never be used in a bathroom again as they said they recommenedtheredry lining system over render, also bondings used in applications that they would never recomend or haveeven thought of, like for instance packing out rsjs ask them about that and they will be clueless, ask them about mixing it with render as well as a lot do and see what they say, at the end of the day i know whats text book and the right way to do things but if an employer tells me to do it a certain way im going to do it,

 

[roughcaster]

You "have" to take what they (British Gypsum) say as gospel, because if you don't. and you wander from their spec and there's a problem, there's no comeback.
Sure, we've all added a little bit of this, or a little bit of that to different mixes, but that's totally different to using different materials, the wrong way round.
You said in your reply to Dazdel, that all old bonding is now being chopped out, because it's either going black and crumbling with damp, and being replaced with render. That's not the old plasterer's fault,, that was the spec at the time,, but the "cement render" you're speaking about Steve, has no spec, and is onto a bonding coat scratch coat,,, (so no difference to 30 years ago, bonding plaster onto brick/block). This will in time will also probably go black and crumble with the damp, then throw off the cement render top coat,
If an employer tells you to do it this way, then that's up to him, but as Micilin said earlier,,where's the spec??? You will "never" see any spec for this method of ""rendering"". It's the wrong way to render. The arguments for this type "rendering"is (if you pardon the pun), full of holes.

Have a read of this link from wall finishing specialists, They're manufacturers/contractors/applicators. count down and click on question 17.

http://www.francofinishes.co.uk/faq.asp

 

[stevethespreader]

You "have" to take what they (British Gypsum) about Steve, is onto a bonding coat scratch coat,,, (no difference), which in time will also probably go black and crumble with the damp, then throw off the cement render top coat.
If an employer tells you to do it this way, then that's up to him, but as Micilin said earlier,,where's the spec??? You will "never" see any spec for this method of ""rendering"". It's the wrong way to render. The arguments for this type "rendering"is (if you pardon the pun), full of holes.

http://www.francofinishes.co.uk/faq.asp[/QUOTE]that bonding coat has paint on one side water proofed render on the other theres not much chance of it getting damp, it a waste of time showing me links to stuff i already know i know what way its supposed to go round for petes sake.
that wall was 0ver 4 years ago now and i can bet you its still up there, and will be in years to come not like the walls of houses that got a good coating of bonding in every room in the house years ago,whole houses floated with bonding? including bathrooms? not for me m8 , came acoss one the other week in a shocking state it was , had a word 2day with a spread i respect and he said that hes not used bonding on its own but used a mixture of sand and cement plus bonding in the same situation,but lets get this right now, i know which way round plaster and s&c goes and if asked to do that again i would