Hi all,

So in the process of completely refurbing my Victorian cottage and am getting quotes for plastering.

Been quite confused by what a number of difference plasters have said. The main problem being that there is a considerable damp problem in one corner of the house. Some people are saying that they would need to insulate board over the top to stop the salts coming through, others that they could chop all the old stuff off and seal it and others that they would use some sort of recovery plaster. Will all of these options be suitable?

The other problem is the massive variation in quotes we have had. There has been a couple for around the £2000 mark per room. The rooms are only about 14m2 and ceilings will need overboarded. On the other hand there was a quote for £450 per room. (we are in the east midlands)

The lower quote was from a plaster recomended to us by a plumber that did a lot of work for us and we were very happy with. Which ends of the scale to people think is most realistic.

Thanks in advance for your advice.

Jimmy

Surely you should get the damp sorted first, and find out if it is condensation or penetrating damp. My house had damp 20 years ago. The previous owner had a chemical damp proof course put in, and the lower 1/4 of the plaster on many walls removed and replaced with a hard plaster. I've read that you need an independent surveyor to check the damp, not some chap from a damp proofing company. Pretty obvious statement I guess.

Hi leif. we have sorted the cause of the damp problem it was due to the guttering which has now been replaced. Now we are just trying to make everything good again. Ta

before you can specify a solution, you need to find out the cause...
simple really, and a no brainer, but youre not to be expected to know what the problem is, only that youve got a problem...
2 grand per room is an awfully large chunk of money considering I could overskim a 3 bedroom house for that, easy...
Surely each individual room should be taken on its own merits as it were?
dunno what 'recovery' plaster is? new one on me but ill bet its dricoat or limelite, 'renovation' plaster might be a more accurate description. its a lightweight, cement based, undercoat plaster designed for use after the installation of a chemical damp proof course, less prone to shrinkage and contains additives to inhibit hygroscopic salts. It still allows the wall to dry out.

Insulating the wall depends on how much plaster is removed. remove more than 50% of the plaster and building regulations state you must upgrade its insulation to meet a target value provided it doesnt already meet a threshold figure of 0.7wm2k (probably wont do)

Insulating the wall will eliminate salts, prevent condensation, eliminate shrinkage problems etc but its not normally specified to combat hygroscopic salts, cant understand why thats been given as a reason at all to be honest?

All you really need to do to combat salts is spray the brickwork with a solution of vinegar, water and washing up liquid.... then render it with dricoat or even just sand and cement with a salt neutralising / waterproofing additive but this introduces shrinkage problems..

but first things first, you need someone who knows what theyre looking for to find out what the problem is in the first place...
easy enough if you know... not so easy if you fail to take all possible factors into consideration...


edit: didnt spot the guttering post till i'd typed it...

in which case, its either dricoat and skim, or insulate board and skim, choice is yours...
if its gonna get insulated, id still be giving it the old 'salt neutraliser' (vinegar basically) prior to installation of the insulation...

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http://www.peterborough-plasterer.co.uk/

Thanks very much cw


The cheapest plaster said that he would seal the damp areas before reskimming to stop any remaining salts etc coming through, would this be sufficient? Dont really know what he means by this?

Ta

me neither? 'seal' the damp areas? what with?
if youve got a penetrating damp problem such as the wall being below ground level and its impossible to stop the water penetrating then you would 'seal' the affected area.. otherwise known as 'tanking'.. then plaster it...
if all youve got is a wall thats had a penetrating damp problem, as yours has, and is now cured then all you need to do is 'neutralise' the salts whilst still allowing the wall to dry out naturally...
best thing to use in these situations is thistle dri-coat
but having experience with this stuff, i now give the wall a good blast of salt neutraliser solution before applying the undercoat plaster for good measure...
I prefer this stuff to sand and cement render with waterproofing and salt neutralising additives because of its ease of use, lightweight density (less prone to condensation problems), its less prone to shrinkage and its ready to skim in 24 hours... in short, its ideal
havent seen the job, so i cant quote for it, but if its just one corner that need a hack off and dricoat, then a whole room reskim, i reckon 450 quid is a lot nearer the mark than 2 grand...

just dont paint the wall till its dried out.... or if you do, make sure its porous... under no circumstances use silk paint because it wont allow the wall to dry out...
when you consider that masonary dries at a rate of approximately 1mm thickness per day then a 100mm thick brick will take 100 days... then youve got the render and the skim on top...
seeing as its probably 200mm thick, and the rain will keep getting the outside wet, then technically, allow 200 days....

'hygroscopic' means 'dissolved within the substrate', when a wall gets wet it picks up the salt and carries it with it as it moves towards the surface during the drying process where it gets deposited in the form of a white crust on the surface..
salt neutralising additives do just that, its simply adding acid to alkali to end up with a neutral ph e.g. no salt...
or in other words....
vinegar (acetic acid)...

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http://www.peterborough-plasterer.co.uk/

one more thing... what you definately DO NOT want to be doing is using a gypsum based undercoat plaster such as bonding or hardwall...
gypsum based plaster will soak the residual water up from that wall like a sponge and turn to mush.. i.e. gypsum plasters deteriorate when they get wet...
you need to use a cement based undercoat plaster such as dricoat, limelight, or just plain ol sand and cement....
the gypsum based skim is fine as its thin enough to allow moisture to pass though it and evaporate as it does so, almost immediatley...

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http://www.peterborough-plasterer.co.uk/

The damp area should be rendered with anti-sulphite render, before being plastered as normal.

If you have had the cheap plasterer on recommendation, ask him to do a room and keep a close eye. Then give him the rooms one by one. Unless there is a need to give the whole job to one, I wouldn't. If you don't like what they do, you are stuck with them or it gets awkward. If he does one room badly, then you have only lost a couple of days wages. Two grand a room for that size is expensive, even if they are going back to the brick. Unless it is lime based heritage work on a listed building or similar.

It should follow that a expensive plasterers will save you money on the decorating, but that isn't always the case.

whats 'anti sulphite render' jozeffo?

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http://www.peterborough-plasterer.co.uk/

Anti sulphite render. Sorry, should have said salt inhibitor.

CW hit the nail on the head. I live in the Mids and if you want an oppinion I may be able to come over. I'm booked up for a long while but I may be able to put you onto a good plasterer.

So got the plasterer back round last night to ask a bit more. He said that the seal was something a bit like a resin that will stop anything else coming through.

Does this make any more sense to anyone?

Not really. It may exist and do the job, but most damp companies insist that their guarantee is only applicable if the correct render additive is used before plastering.