Plastering question

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I have a section of plaster which needs to be removed. EML needs to be applied onto the brick work and then re-plaster and re-lined.

The area requiring replastering is about 3ftx2ft. The plaster is about 12.5 mm deep.

Some questions.

1. Can the EML be screwed in place (rather than nailed in)

2. Once the EML is in situ, the wall be rendered with bonding plaster and then after (say) 24hrs that area will be skimmed (or can it be skimmed on same day?).

3. How long should I wait prior to relining? Is a week a good yardstick?

Cheers
 
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1. Can the EML be screwed in place (rather than nailed in)
You could I suppose but not sure what benefit that would that give. I use galvanised clout nails either direct into the block work or where the mortar course meets brickwork; they are only there to hold the lath in place until you get the first layer of render/plaster on there.
2. Once the EML is in situ, the wall be rendered with bonding plaster and then after (say) 24hrs that area will be skimmed (or can it be skimmed on same day?).
I generally prefer to use render base for such jobs, Bonding is really for low suction backgrounds, what do you have? You must make sure you damp it all down well & control suction or it won’t stick, will craze like hell & fall off. Apply the Bonding in two coats, push first one well into & only just covering the lath. Once the first coat is set (say 2 hours), apply the second out to required depth you can finish over Bonding after another couple of hours; if you let Bonding dry out it will suck like hell & you’ll be back to square one.

3. How long should I wait prior to relining? Is a week a good yardstick?
What are you relining with, is it dot & dab plaster board? If you’re over boarding, why bother with the skim coat just fill out flush with Bonding. A conventional base & skim of around 15mm can take up to 4 weeks to dry out thoroughly; even though it may look OK it will still have residual moisture content & if you board over too quickly, you will get condensation & nasties growing behind the board. Why don’t you just fill out flush with Bonding, tape the joins & re-skim the entire wall?
 
First of all let me say that the EMl will be applied to breeze blocks and more specifically celcon blocks (not brickwork).

The plaster currently on (don't know the trade name for it) is the dark pinky stuff.

Richard C said:
You could I suppose but not sure what benefit that would that give. I use galvanised clout nails either direct into the block work or where the mortar course meets brickwork; they are only there to hold the lath in place until you get the first layer of render/plaster on there.
Only that I did not want to have any undue issues with hammering nails in.

Richard C said:
I generally prefer to use render base for such jobs, Bonding is really for low suction backgrounds, what do you have?
100mm standard celcon blocks.

Richard C said:
What are you relining with, is it dot & dab plaster board? If you’re over boarding, why bother with the skim coat just fill out flush with Bonding.
Lining paper, hence the requirement of a skim coat.

Cheers
 
Only that I did not want to have any undue issues with hammering nails in.
With Celcon/Thermalite blocks you won’t, you can almost push them in! When fixing the lath knock in all the nails ¾ of the way first then go around the lot with a single light hammer blow, just enough to ground them, this stops nails you’ve already driven coming loose as you go.

100mm standard celcon blocks.
They are high suction which Bonding doesn’t like very much unless you thoroughly prep it & are very careful during the first 1 ½ hours during setting. You need to damp down really well first (2/3 times) & apply only enough Bonding to just cover the lath with your first coat, then you need to keep your eye on it as it will probably need a damp down with a spray bottle & a bit of a troweling off to avoid it drying out too quickly & crazing; but don’t overdo the water or it’ll turn to mud & have no strength. One set damp down again & apply your second coat of bonding but, once again, keep the spray bottle handy until it’s set; leave it slightly longer before you skim, maybe 4 hours but don’t leave it overnight or you’ll have problems with suction on your skim coat. I've even damped down again the following day to prevent it crazing.

Lining paper, hence the requirement of a skin coat.
Oh OK but that’s a shame as your going to all that trouble with the repair work. Lining paper has it’ uses I suppose but, personally, I can’t really see the point in the stuff other than a quick "cover over" for defects. The Decs will disagree with me but it’ll never compare or look as good as a quality plaster finish. As you may have gatherered, I don’t like the stuff very much. :LOL:
 
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Many thanks for your very informative reply Richard C.

I appreciate that the instructions you gave me are pretty clear but I think this job is probably outside my capabilities and more specifically correctly applying the bonding.

I think perhaps I should look for a pro who could undertake this repair.

Is there someone in central London that you could recommend to do this correctly (apologies if such questions are not strictly allowed). You can PM me the info if you have any ideas.

Cheers
 
I appreciate that the instructions you gave me are pretty clear but I think this job is probably outside my capabilities and more specifically the bonding process. I think perhaps I should look for a pro who could undertake this repair.

As I live in Norfolk, I can’t recommend anyone specifically. I did know someone very young & very good in the London area but he’s now followed my own footsteps into tiling & does nothing else ; I still do this type of work because it fits with the renovation “package” I offer & it really interests me. It does require specific knowledge & skill so you really need to be very careful who you pick to do it, particularly in London. Many who palm themselves off as plasterers are really only competent at skimming boards &, even then, some aren’t even very good at that. Go on personal recommendations & chose someone who has experience at this type of renovation work & look at previous jobs, it’s far removed from what’s required for plasterboard skimming or even new builds.

Why not have a go yourself as you originally intended; it wasn’t my intention to frighten you off, it’s just that some see plastering as no different to a general DIY work. With the advice I’ve already given, you probably already know more than some who will quote you to do the job &, if you need more help, both myself & the other pro’s on here will gladly give it. You won’t need a perfect finish & if you’re really intent on the dreaded lining paper. ;)
 
Thanks very much again for the added info Richard C.

Richard C said:
Why not have a go yourself as you originally intended; it wasn’t my intention to frighten you off, it’s just that some see plastering as no different to a general DIY work
There quite a few jobs that I don't mind doing myself. I am not sure about this. I will have to think about it harder.

It's just that I was going to give the room a couple of coats of paint on the walls afterwards and if I fluff the plastering then I will be back to square one which would be irritating especially as this work will be carried out in the main bedroom and hid will make my life miserable (or should I say more miserable).

Let me ask you these final questions please.

1. For clarity the layer(s) of bonding and skimming are done with the same plaster ie the dark pinky stuff, correct?

2. With the knowledge that the plaster is on celcon (breeze blocks), do you think that I can get away with just applying one layer of bonding plaster and then skimming?

3. I was going to remove the cracked plaster by using a cutter (don’t know what kinds of issues I may find underneath the plaster hence using a cutter). So should I cut the plaster at 90deg or at an angle (ie outwards kinda like a soup bowl).

4. After having done the bonding, you stated that the final skim should be done when the bonding is dry ie 4hrs or so. So doing the skimming on the following day is a define no no.

Again many thanks for all the info

Cheers
 
1. For clarity the layer(s) of bonding and skimming are done with the same plaster ie the dark pinky stuff, correct?
No Bonding is a base coat plaster of which there are several; it has a course texture & is usually 10-14mm thick in total but can be much thicker. Finish is a different plaster, much finer & is usually between 3-5mm thick in total. Depending on weather I was just blending in a repair or re-skimming the whole wall would dictate if I finished level with the Bonding coat of left it 3mm below the surrounding wall. The colour of the plaster is not relevant; it can be pink or grey depending on where in the country the Gypsum was mined.

2. With the knowledge that the plaster is on celcon (breeze blocks), do you think that I can get away with just applying one layer of bonding plaster and then skimming?
I wouldn’t advise it; you’re more likely to disturb the lath with the amount of troweling needed, best to let the first coat set & hold the lath firmly in place. High suction blocks would cause one thick layer of plaster to dry out unevenly causing classic symptoms of crazing & poor adhesion, need to build in two layers over your lath to avoid problems.

3. I was going to remove the cracked plaster by using a cutter (don’t know what kinds of issues I may find underneath the plaster hence using a cutter). So should I cut the plaster at 90deg or at an angle (ie outwards kinda like a soup bowl).

Using a scraper is more usual, if it’s blown it’ll just fall away; I had assumed your problem was cracked block work, is that the case? With plaster repairs avoid straight edges as the won’t key very well, jagged uneven edges are good news as they provide a good key.

4. After having done the bonding, you stated that the final skim should be done when the bonding is dry ie 4hrs or so. So doing the skimming on the following day is a define no no.
It’s not a definite no, no just makes life a little easier to do it the same day. You can skim next day, next week or even next month but as the base plaster will be much dryer or even completely dry you will need to control suction again or the finish plaster will craze.
 
Richard C said:
Using a scraper is more usual, if it’s blown it’ll just fall away; I had assumed your problem was cracked block work, is that the case?
The plaster is cracked as a result of a stress crack. The plaster is not blown and is still holding well onto the celcon blocks. I am not sure as to the condition of the celcon blocks underneath.

Not sure what a scrapper looks like any link to a pic?

Richard C said:
With plaster repairs avoid straight edges as the won’t key very well, jagged uneven edges are good news as they provide a good key.
Perhaps after I have cut out the plaster I can use a hammer and chisel around the perimeter to make edges jagged.

Richard C many thanks for all your words of wisdom.

Let me have a head scratch and see if I am up to this.

The thing that has got me worried about doing this is this suction and moisture / water aspect which is obviously an important part of the process.

Cheers
 

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