how to patch up a 2cm line of plaster?

[Tin Soldier]

Hi there,

 

I've had to alter the size of my door openings, lowering the head by 11cm, which for some reason were left too big by panel company and I never though to check before everything was boarded and skimmed, I've done this utilising cls timber, and faced the timber with plasterboard so that its just shy of level with current skimmed walls.

 

so this has left me with a problem. my architraves are 9cm, which leaves 2cm of bare plasterboard above (between architrave and skimmed wall) and unfortunately I'll have to do this for every door

 

What is the easiest method of patching this up myself - without getting plasterer in. the walls are unpainted, but are skimmed.

is there ready made plaster/product that I can use to fill and sand?

I'm worried about it cracking as doors will be opened and closed etc - are there any meshes/ alternatives to add in to stop that from happening?

 

any advice greatly appreciated

 

Scott

[Mr Punter]

Toupret filler is very good and easy to sand. You will need to fill and sand a couple of times.

[MarkyP]

if you are patching over an underlying joint between your new plasteboard and the existing skimmed walls (which it sounds like you are) then I would use plastering scrim tape over the joint before filling. Plasterboard jointing compound (used to fill joints in dry lining) is relatively forgiving stuff to use and is very easy to sand. You'll need a couple of coats, first one to get a skim over the tape, and a second to feather in, then a light sand to smooth any blemishes. You can get tubs of ready mixed jointing compound from most builders merchants and more trade focused sheds. I find it easier to prime existing plaster (unless already painted) with weak PVA solution first (leave to dry) as the joint compound stays live longer and is easier to feather out with a trowel.  if you need to finish sand use very fine grade paper or you will get visible swirls when you paint.

 

don't confuse with ready mix patching plaster products. This stuff is often grey colour and is handy for some jobs but is hard to sand, often dries a bit harder than the original skim so you can struggle to sand back and get a clean joint.

[PeterW]

Agree with the above - scrim is probably worthwhile here as otherwise due to doors slamming etc you may get cracks. 

 

Toupret or Alabsatine filler are the best here - also worth getting a very wide filling knife such as a 6” metal one to get the joint as flush as possible. You will end up filling both an 1” from the old plaster too as you’ll have to get the old stuff off to start with to get the scrim to bond onto the board below the skim coat. 

[Tin Soldier]

are you saying I need to chip off the skimmed plaster in order for tape to adhere to it? 

[MarkyP]

personally I wouldn't but there's more than one way to skin this cat. The tape will adhere to plaster in my experience. But you will have to skim over the tape, and then feather out into the body of the existing plaster which some might find a fiddle as you have to cover the tape suffuciently to avoid it grinning through. this is why dry lining boards have tapered edges, to ensure the tape sits below the finished surface.

 

If you chip back the existing plaster you can tape in the recess and then fill flush to the old plaster. Chipping back cleanly can be fiddly. And you will still have a joint between the old skim and filler.  This wont be as crack prone but still might hairline crack with doors opening and closing.

 

edit to add that the latter will be easier to get a clean finish if you haven't done much of this sort of thing before.

Edited February 4, 2019 by MarkyP

[Tin Soldier]

ok thanks gents, very much appreciated, I'll have an attempt at it tonight and see how it goes

[MikeGrahamT21]

British Gypsum Easifill - its a jointing compound which has been spoken off, very easy to get a smooth finish and sands well, but be prepared for a LOT of dust

[Dreadnaught]

A left-field comment.

 

If in your build you will have MVHR then that requires a ventilation gap under each door to allow air to circulate between rooms.

 

One build I visited in Hampshire decided to put those gaps above the architrave at the top of the doors instead and leave the doors without their gaps beneath. I thought it was quite a good idea. 

 

An option for you while you're doing it?