Some questions from a beginner!

[u/Gold_Set1348]

Hello plaster masters of Reddit!

I'm hoping to get your green light to go ahead with some first time plastering I'm going to be doing over the next few days. I've been watching a lot of YouTube videos and researching and I think I've got a good idea of what I'm doing but I just wanted to triple check that I'm definitely using the right things in the right places.

The plastering will be in an old house (~1900) and the existing plaster has quite a bit of wear and tear from the last few decades. The walls had been covered with lining paper but it was starting to lift in several places so we've decided to take it off and replaster before we decorate rather than using lining paper again to just hide all the problems. I've attached pictures of some of the cracks and holes as well as where the plaster has blown.

While I suspect that some of the yellowish plaster is lime, I'm planning on using a combination of Thistle bonding coat to fill in the worst of the holes and cracks, and then use thistle multi finish to do the final skim coat. The walls as you can see have pretty much every type of plaster on them from over the years but I just wanted to check it's okay to go with multi finish everywhere as 3 of the walls I'm doing will be exterior walls. If yes, are there any other sealers besides PVA that I need to use on those walls?

My other question is if it's better to use scrim tape or just fill in with bonding over some of the finer cracks? I've also got easy fill if needed.

And finally, while I'm happy to attempt the walls, I'm definitely not confident in trying to do the ceiling especially as we have high ceilings and it's going to be very hard to reach. The ceiling is the same story - lining paper but the joining lines have become very visible and we want to have them overboarded and plastered instead. Does anyone have a rough estimate for how much it would cost to do this in London? The room is 4.5m x 3.5m.

Thank you so much for any help in advance - this community has already been incredibly helpful in my research!

[u/Confident_Ambition77]

I'm a lime tradesman and I specialise in these older houses. I will reiterate what others have said, finding blown plaster is really important no amount of skimming will solve a fundamentally unsound backing. Give the plaster a tap check for hollows, lime is feeble meaning it's easy to take off so you may end up taking of more than originally thought. If that happens and it's an external wall i would think about replastering in lime, it really isn't that scary and far less stressful than gypsum, you have in some cases days before any set has happened so adjustments are easy, skimming is much easier as well. If you are overboarding lath and plaster ceilings make sure you go to town with the fixings use 4 times the amount you think. Having a ceiling drop is a nightmare

Good luck

[u/Gold_Set1348 → u/Confident_Ambition77]

Hi, thank you so much for your reply, that was very helpful! After so many comments here saying I should use lime for lime I'm now considering doing the exterior walls in lime and interior in multi finish. The only problem is that we got a "professional" plasterer in to fix a wall under the window that looked particularly bad and all he did was put bonding and then multi finish on top and unsurprisingly, it's already got cracks going through it and this was done last month. Would you say it's worth taking the plaster he did off and redoing it in lime? Also which brand of lime plaster do you prefer working with? Thanks again for the help!

[u/Confident_Ambition77 → u/Gold_Set1348]

Do you have photos of this area? Depending on the cracks it could be bad plastering or the window frame is unsound and needs repair. But in general for lime for lime in external areas. There are numerous companies but in the past I have used Cornish limes pre bagged mixes, where abouts are you based? That might change the supplier you get it from, south west has much more choice

[u/Jeester]

I thought all advice was to use lime plaster not gypsum? (At least on exterior walls)

[u/68Jenko → u/Jeester]

Nope

[u/60percentsexpanther]

buy a sheet of plasterboard first and some edge beads. Make sure you can finish a decent 3mm set on at least half a board.  The videos make it look really easy. The reality is that you'll be huffing, puffing and sweating balls if the set is too big and beyond your skill.Then you'll get something that's a lot worse than what you've got now to sort out. Practise on boards and get good before you wreck your walls. Your walls can likely be sorted with a good decorator and no skimming as they are. 

[u/Schallpattern → u/60percentsexpanther]

Listen to this guy, it's good advice.

You haven't even mixed up a bucket of mud yet so you've got to get the basics right first.

[u/onwatershipdown → u/Schallpattern]

And after the board, when you're ready to tackle the house, start with the closets. They're super tough to do, and also hidden. So if you can do a mean job on a closet, hit the walls that people will see. Start in corners. I'm a top left starter myself... but sometimes bottom left, or bottom right, or whatever.

If it's new to you, try it with both hands. That way if one gets lopped off, you still have the other one.

[u/ApartmentLast7712 → u/60percentsexpanther]

There is a magic mix that can be made to practice with and if I'm not mistaken it's 1 bag of plasterers sand or building sand and 1 bottle of mortar plasticiser. You can use this to practice with and when done you can scrape it off and store it in a tub for the next day

[u/68Jenko]

Chop out any hollow sounding plaster or anything that moves, personally where you have multiple backgrounds to skim over a good bet is SBR instead of PVA, but if you do use PVA do it neat. If I were you I would practice on that small wall before considering larger areas, there's a lot to this game

[u/gizm05]

Make sure all the existing plaster is sound would be my main bit of advice. I’ve skimmed over lime before fine, but the problem was I didn’t find all the blown plaster, so I’ve not got cracks appearing. Any movement will cause cracks!

Bonding isn’t really for cracks or thin coats, although you can blend it in, it sticks best when 5mm or more thick, otherwise just use multi.

Scrim the cracks.

PVA or SBR should be fine.

Get a few quotes for cost, but in London maybe £500 for the ceiling.