Maximum Plaster Thickness on Plasterboard

[boatmad]

Could someone pleasel et me know what is the maximum thickness of plaster that can be applied to plasterboard.

 

[roy c]

Explain the situation that you want to plaster and why it might need to be thick....

 

[boatmad]

Want to block off a door between lounge and dining room, door and frame have been removed. It would be easier to fill the gap with a stud wall rather than block, wall thickness including plaster is 137mm even using 100mm timber and 12.5mm board still only gives 125mm wall thickness giving 6mm plastering required each side.

 

[roy c]

Why dont you pack one side out ( say 5 or 6mm) and then plaster board?

 

[Richard C]

Preferably pack out the boards as suggested but, if not, put a skim of Bonding on there first to bulk it out & then skim with Multi. Should be done in one hit, Multi straight after bonding has firmed up; it’s a common method for over skimming deep pattern Artex ceilings.

Personally I would use Bonding to fill out flush with the surrounding wall, tape the joins (3 overlapping layers) & Multi skim the whole wall; it’s the only way you will stand any chance of avoiding differential expansion cracks between the solid brick wall & stud infill.

 

[boatmad]

That is an option, how much should I leave between the existing wall level and the new wall level, I was hoping that the plasterer could make up the difference without the need of packing etc.

 

[Richard C]

That is an option, how much should I leave between the existing wall level and the new wall level, I was hoping that the plasterer could make up the difference without the need of packing etc.

Whose doing the board work? Which option, spacing out or bonding before the skim? Either way, your spread will know what to do if he's any good. But as I said previously, my preferred option would be;

I would use Bonding to fill out flush with the surrounding wall, tape the joins (3 overlapping layers) & Multi skim the whole wall.

If you just board out to existing level, skim & blend, depending on how good your spread is, the chances are you will probably still see the join & where the door was. Even if he does a tremendous blending job, there is still a big risk it will crack around the original door opening due to differential expansion where the two dissimilar materials meet. To prevent cracks, the joins must be taped that will require blending out over 300 -500mm if your not going to see it, not easy even for the experienced; if your buying a spread in, it’s quicker, easier & probably no more expensive to skim the whole wall.

 

[boatmad]

Thanks for the advice Richard, I was hoping to do the partition work myself to keep the cost down and then get a professional plasterer in to do the whole wall on both sides. Do you suggest that I abandon the partition wall idea to prevent the cracking possibilities and revert back to blockwork and traditional plaster or would reskimming the whole wall prevent this from happening if I brought the plasterboard level to the original level as suggested?

 

[Richard C]

Do you suggest that I abandon the partition wall idea to prevent the cracking possibilities and revert back to blockwork and traditional plaster

Most definitely the best way to do it but you should still tie the block work into the main wall. Spread will (should) chip back the original plaster & fill out to surrounding wall level with base plaster, tape & then re-skim the whole wall. Done properly, you will never see it or hear it, as opposed to a stud infill; I’m something of a “tap, tap” maniac when let loose on a prospective property purchase.

or would reskimming the whole wall prevent this from happening if I brought the plasterboard level to the original level as suggested?

Rewind a bit; don’t stud/board out to the surrounding wall level, chip back the plaster to the blocks/bricks all around the door opening around 200mm, fit the studs so the boarding overlaps the blocks (a few daps of board adhesive or grab adhesive required here) & butt as close as possible to the original plaster (original plaster depth will dictate board thickness used). Fill any gaps & then base coat out to original wall level (over the boards & blocks); tape the joins & finish skim the whole wall. Done properly, the success rate is high but nothing is guaranteed however & there is always a danger it will crack along the join where the original block wall meets the plasterboard. Blocking in is still best &, to be honest, not much if any more work.

 

[boatmad]

Thanks Richard from preventing me from making a possible mistake. Having thought about it it's obvious that different materials will behave differently and lead to cracks. Blockwork it is then, don't want to be forever filling in cracks after all it will be in my lounge and I will see it every day which will drive me mad!!

Thanks for the advice.

 

[NickB_99]

Having thought about it it's obvious that different materials will behave differently and lead to cracks. Blockwork it is then, don't want to be forever filling in cracks

I had a similar dilema when getting some openings closed up my in current place.

I opted that the builder filled in the openings with blockwork. (I know where Richard C is coming from with the 'tap,tap'!)

However, I forgot to specify plaster finish, so he finished with drylining over the blockwork
The original plaster wasn't cut back to any significant amount, but was taped. Unfortunately this has led to some slight cracks 12 months on
- and a difference in tapping!
My own fault I guess !

So would suggest if you go for the blocks, complete the job properly with a base plaster to match surrounding wall.