Plastering on bare walls or over plaster (or both)?

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We are coming towards the end of a loft conversion. Where the new stairs enter the loft the wall to the side of the stairs is half plastered (up to the height of the old first floor ceiling) Above this is a bare limestone wall and is somewhat roughly built. I was planning to dot & dab plasterboard onto the bare wall and then have a plasterer skim the entire wall (over the existing plaster and new boards) but having done this eleswhere in the house the finsih hasn't been great and it is clearly obvious where the two backgrounds join and there are hairline cracks beginning to form. The old plaster is also very thin - only about 20mm max - so i'm doubtful i'll be able to dot & dab on the wall below and get it level? Therefore, we wondered if it would be better to wet plaster the bare wall up to the level of the existing plaster and then skim the lot?

The existing plaster is covered in some sort of pink paint (maybe called 'distemper'?) and i'd guess this doesn't provide an ideal background for skimming (the other wall which was done was coated with PVA before skimming but still hasn't give a great finish). Would we be better removing the old plaster back to the bare wall and wet plastering from scratch?

Not really sure which way to go with this - any suggestions would be greatfully received
 
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What sort of area is unfinished, and what area is the existing plaster?
If it's not too much I would be inclined to hack off the existing and do the whole wall from scratch.

But it really depends on finances, time, mess etc etc.

You could consider a horzontal "dado" type thing, then both areas would be separate, and a small step wouldn't be noticed.
 
The wall is about 10sq.m total and i'd guess its about half and half, maybe slightly more has existing plaster rather than is bare walls. Not so keen on the dado idea?

If we go with taking off the existing i would do it myself and then get plasterer in. We took down 35-40 sq.m of very old plaster and lath ceilings last year - there's no way the mess could compare to that so i think we could cope with the mess!! Time isn't that crucial either.

If i strip the plaster off then, what needs to be done to the wall (if anything) before the plasterer can come in and do his stuff? Will it need leveling off to some degree? I suspect the wall that's already plastered will be more even than the rough wall which used to be in the loft so maybe only the top half will need levelling off if at all?

Is it best to wet plaster the bare wall, or dot & Dab plasterboard on the entire wall and skim the boards?

Just out of interest, how will the plasterer go about plastering a bare wall? Do they just apply backing plaster to the bare wall, then skim on that?
 
Dot & dabbing boards & blending will always present a risk it will show & even crack where the 2 meet. The problem arises due to different expansion & contraction rates between the 2 substrates; it can be successfully done but the join must be thoroughly reinforced. I always recommend & prefer to go with a proper float & set render base with a new finish skim over the whole wall but, again, the “join” must be reinforced or there is still a risk it will crack. Distemper on the wall shouldn’t be a problem if it’s sound & the wall is properly prepped so not sure why your plasterer didn’t achieve a good finish the last time.

If the existing plaster is sound there is no point in taking it off, it’s just unnecessary work & even very uneven surfaces can be sorted out with a little work. I would not advise doing any prep work without consulting a decent plasterer first & I mean an experienced plasterer, not just a skimmer. Personally, I prefer to do my own prep work as it’s the only way I can be sure it’s been done properly; some don’t mind but you must follow their instructions explicitly. The thing to remember is if you do the prep & the plaster falls off, it could be blamed on you; if your plasterer does the prep & it falls off it can only possibly be his fault! It sounds like a good way to save time & money but in reality it saves very little to someone who knows what they are doing & can be a hindrance if it’s not done properly.

Is it an external wall? Is it solid or cavity? This may dictate the way it’s done.
 
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Cheers Richard. I've no problem leaving the prep work to the plasterer and like you say, it makes sense that if something goes wrong - he can't say its down to my prepping if he's done it himself!! Think i'll get a few plasterers to come and have a look and see what they suggest. My only problem with not taking off the existing plaster is i really don't want the 'join; to be visible. If there's a chance it'll be visible, or worse still, it will crack, then i'd prefer to spend the time taking the existing stuff off and then incur the cost of someone putting it back on!!

The wall is a party wall built from limestone and is quite roughly constructed, particularly in what was the loft. The wall is at least 500mm thick. Its not a cavity wall in the sense of cavity walls we know today, but i know from experience elsewhere in the house that the walls do have some hollows in them in places. I took a door frame out that abutted a wall elsewhere in the house and a small piece of limestone came out of the wall, behind which was a cavity big enough to fit my forearm in!! Was quite alarming at first but its been there for over 100years so who am i to question it!?!

Do you think a plasterer would be able to get it done in the same day? As I said, its on a straight flight of stairs with a landing about 900mm long at top and bottom - height on landings is about 2.6m and headroom is 2m on stairs (as required by BRegs).

As for previously - on the GF to FF stairs, i think what you say is correct, the guy simply didn't reinforce the join properly so the crack has appeared. We had a different couple of guys to do a different room which has distemper on the walls and the plaster has bubbled - presume they didn't prep it properly. Certainly wont be recommending them to anyone!!
 
My only problem with not taking off the existing plaster is i really don't want the 'join; to be visible. If there's a chance it'll be visible, or worse still, it will crack, then i'd prefer to spend the time taking the existing stuff off and then incur the cost of someone putting it back on!!

It really shouldn’t be a problem if it’s done properly; you stand a much better chance of avoiding cracks if the new plaster work is of similar make up to the old (i.e. it wouldn’t be if you dot & dab); but even then it shouldn’t really be a problem if done properly.

The wall is a party wall built from limestone and is quite roughly constructed, particularly in what was the loft. The wall is at least 500mm thick. Its not a cavity wall in the sense of cavity walls we know today, but i know from experience elsewhere in the house that the walls do have some hollows in them in places. I took a door frame out that abutted a wall elsewhere in the house and a small piece of limestone came out of the wall, behind which was a cavity big enough to fit my forearm in!! Was quite alarming at first but its been there for over 100years so who am i to question it!?!
Shouldn’t be a problem, I was more concerned about possible damp.


Do you think a plasterer would be able to get it done in the same day? As I said, its on a straight flight of stairs with a landing about 900mm long at top and bottom - height on landings is about 2.6m and headroom is 2m on stairs (as required by BRegs).
Would be a very long day methinks & I would say unlikely, especially over stairs with all that jumping up & down on trestles etc. I certainly wouldn’t attempt it but then I’m getting old & slow! 22mm overall is quiet thick & a render base (or a base coat plaster) will need to be built up in at least 2, possibly 3 stages to avoid cracking; this will take time & the render has to set before skimming; & then he’s got to skim over the whole wall, old & new.

As for previously - on the GF to FF stairs, i think what you say is correct, the guy simply didn't reinforce the join properly so the crack has appeared. We had a different couple of guys to do a different room which has distemper on the walls and the plaster has bubbled - presume they didn't prep it properly. Certainly wont be recommending them to anyone!!
What can I say! ;)
 
Cheers Richard,

Was hoping they'd be in and out in a day but if you don't think its possible then thats the way it'll have to be! Will get a couple of local plasterers in to have a look and see what they think we should do with it now that i've got some knowledge myself about the different options.

Will let you know how it goes!
 

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