Plastering over old plasterboard

[Steve28]

My father in law has asked me to plaster his spare room, it's a new build house and he's stripped the wallpaper back to plasterboard, however some of the plasterboard has the surface torn from the wallpaper being taken off and I don't want to re-plasterboard.
How do you suggest plastering that, should I seal it with wickes bonding agent first or can I use pva?

Cheers

 

[henry]

You can use wba or pva it all depends if the paper has come off the board face showing the gysum core .In any case you will have to tape up if the areas are damge. For me I would wba the lot.

 

[Chris W]

id scrim the exposed bits..
just be on safe side innit...
check it aint covered in wallpaper paste...
and use board finish, not multi..
but yeh, pva or bonding agent like henry says..

 

[gps]

pva is all you need mate for the life of me unless its a really porus surface and I mean really porus then its pva all day long never had any problems with it.

 

[spunky]

Bond it completely seals what it goes over if the papers torn and the boards areva bit f**k*d I can see where he's coming from it's not just to control suction, if it's a porous surface like week old hardwall you're better off with pva bondit etc is for low suction low key substrates

 

[Chris W]

and... still.... some... people... havent... yet.... figured.... out.... that.... bonding.... agent .... isnt... for.... suction....control....pva.....is.....for....suction...control.....bonding....agent....gives.....you....a....mechanical.....key.....on...low......suction.....backgrounds.....it.....will....also.....bond....friable....surfaces.....prior....to.....suction....control.....being....dealt...with.....however.....sometimes.....you...might....find....that....a...bonding....agent...will....do....both...jobs.....unless.....its....silly...high...suction....in...which...case....your....f**k*d.....

 

[bubbles65]

my eyes are hurting........

 

[Steve28]

Cheers lads,

The boards aren't too damaged, it's just the front of it has been peeled slightly in several largish patches that I don't really think taping would be an option with. The boards core hasn't been exposed. I was just worried that Pva and plastering would be the Equivalent to plastering over patches of wall paper on Walls when skimming, which is a bit of a no no. I've just never come across this problem before.

 

[Chris W]

my eyes are hurting........

ive sat and put up with people read stuff to me like that... says it all mate... :RpS_laugh:

 

[Chris W]

Cheers lads,

The boards aren't too damaged, it's just the front of it has been peeled slightly in several largish patches that I don't really think taping would be an option with. The boards core hasn't been exposed. I was just worried that Pva and plastering would be the Equivalent to plastering over patches of wall paper on Walls when skimming, which is a bit of a no no. I've just never come across this problem before.

point is, old boards suck like f'ck... cos theyve had something on em, your never sure which way its gonna go...
dont overdo the pva cos youll kill every last bit of suction, or use a bonding agent which will give you back a mechanical key whatever the suctions like...

wba prolly the safest bet but i'd prolly just p'ss wet pva it depending on the area size and just have it...

 

[johnnyh]

evening to you all,

i am having a f**king nightmare skimming some boards. i'm not a plasterer but i've done a few dozen walls over the years and although i'm a bit slow, i usually do an alright job.

anyway, situation is this; the renovation of my house was started by the previous owner who put up a fair bit of studwork with bare plasterboard. i have finished what he's started and added more boards where necessary but when i've started skimming, the plaster's going off dead quick on the old boards.

first thought was the plaster's gone off but on the walls that have some old and some new boards i noticed it's fine over the new boards but goes off within seconds on the old boards so you can imagine what a pain in the arse it is. i guess the 'old' boards are anywhere between 3 and 8 years old as i bought the house 3 years ago and the guy before me had it for 5 years before that. there's never been any paint or anything else on the old boards.

i am using thistle board finish and i have tried spraying it with febbond/water and no improvement.

what's going on?

 

[lctanner]

you will need to kill the sucton mate......WBA

 

[lucius]

BG do something for damaged boards when taping and jointing but probably loads of money, regarding last post old boards always suck up PVA is good enough to control it.

 

[johnnyh]

i sprayed the second wall with water and then the last wall with pva but it's not made a blind bit of difference... i dunno what ratio i just did it as i would have done a rendered wall maybe i need to do a stronger mix of pva? what would you suggest?

me elbow's killing me!

 

[lucius]

Several coats of 4 to 1 or whatever it says on the tin as some are better than others,

 

[johnnyh]

ok cheers, i'll try that tomorrow.

does the pva need to dry between coats or not?

 

[lucius]

Yes but dont take long, some like to skim on the last one when its going tacky i dont but just another debatble thing.

 

[johnnyh]

Thanks a lot for the advice,

i finally got round to skimming the rest of the room and although i couldn't get a perfect finish as it seemed to drag a bit, it didn't go off too quickly. i gave it a 4 to 1 coat of pva then got waylayed for two weeks then gave it another 4to1 coat and skimmed it an hour later. to be honest i've never actually used pva at the dosage it says on the can. i've always used it just milky but the 4 to 1 is pretty thick and sticky but it did the job.

anyone explain why old boards suck up so badly? i would have thought they were as dry as they were ever gonna be when they came out of the factory...

 

[Chris W]

the paper covering has a sort of water based waxy finish to it when new thats gives a perfect rate of suction for finish plaster..
over time it sort of dries out / disappears and what your left with is a sheet of bone dry paper over a core of even boner dry plaster... hence the silly suction levels on old boards...

 

[Chris W]

this is one of the reasons (apart from damage, obviously) that the top board on a pallet of new boards is always face down... and theyre stacked facing each other...