Dot Dab Plaster wall - 35mm box? Plasterer at odds with electrician

[JLeague]

As part of my spec I said that I wanted 35mm back boxes. The walls have been taken back to the brick and will be dot and dabbed with plasterboard and then skim finished.

Electrician said that he can just screw the backbox onto the wall without digging into the brick because onces its dotted and dabbed the wall will come forward 35mm and cover the box.

Plasterer is adamant that is wrong and has said that he will do dot and dab but the wall will not come out as much so the boxes will protude.

 

[Baddegg]

Everyone’s available for the right price and any works on that scale would’ve been planned months and or years in advance so they would’ve been available, not denying they are obviously very good spreads, it’s a lovely finish, I just don’t agree with your statement that the building contractor HAD to go abroad for the skill set and I stand by my statement it’s all about money, I’ve mates who’ve worked with Russian tilers in places like Nando’s who are no better than local boys but the difference is they are cheaper work 20 hrs a day and don’t dare complain about working conditions or health and safety....

 

[OnlQQker]

="Mike Johnson, post: 1652630, member: 43554"]
Hah you have been reading too many blogs on Facebook re French building, walls do not breathe they allow water vapour to pass, in the UK we have more water vapour outside our buildings than inside, but we don't get many solid brick walls since the victorian times, in 1954 when the building regulations first came out cavity wall construction became the normally accepted construction method and the introduction of two coats of Browning and finish became the norm and if you ever saw how much interstitial condensation happens on the inside of a cavity wall you would not question its permeability.
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I have been in many a listed building which has been patched up with sand/cement on the inside and caused no end of havoc.

 

[Mike Johnson]

We will have to agree to disagree, when you work exclusively in that sector the mind set is totally different, on the first project for HV we had six different sets of sub-contractors until we found the ones that suited our work ethos, those guys are now almost exclusively on HV projects, and incidentally the H&S is of the highest standard as it is in the Joinery shop which makes all the internal fittings, in fact during one of the builds they caused a shortage of Walnut veneer as they bought all they could get hold of to enable book matching the 4.5M high doors, all forty of them.
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I have been in many a listed building which has been patched up with sand/cement on the inside and caused no end of havoc.

If they where listed buildings where was the Preservation Officer, Architect, Structural Engineer, or even the Quantity Surveyor when this was going on.

 

[Deuce]

Thanks

So it seems plasterer was correct - 10-15mm for adhesive, 12mm plasterboard, 3mm skim so about 25-30mm.

I have just spoken to the electrician and he said he had quoted and assumed the new plasterbaord would cover 35mm - if I still want 35mm boxes then its extra or he can fit 25mm boxes which he said really is what everyone asks for.

I am on a tight schedule and for 30 sockets he is looking at 2/3 days more work - I might just have to bite the bullet and go with 25mm boxes.

We're doing the same right now and wanted 35mm boxes, but as per your sums above, even a 25mm back box once dot/dabbed, the board and then skimmed becomes a 30mm deep box - which actually was more then sufficient for the switches and sockets we're using - so it became a none issue.

Are you sure 30mm depth isn't enough anyway? The only ones we had to use a 35mm deep box for was a FCU and an underfloor heating thermostat. The rest (LAP flush, screw-less switches and sockets) all fitted provided there was a little over 25mm depth, which there always will be with dot-dab and 12.5mm board + skim.

In the end we actually went for using foam adhesive in place of the dot and dab, and we used 15mm packers to ensure the plasterboard was spaced sufficiently proud from the block wall as we mounted each board = reliable 30mm depth across all back boxes and no unnecessary chasing.

 

[cliffed]

The PD boxes were the best….

 

[telectrix]

dot& dab is the work of Satan. dhould be banned outright. lazy man's way of finishng off a wall theat should be plastered properly. our house was done in 1956 and most is still as good as when originally done. then again. all internal walls are made of brick. not some ubder seasoned kiln dried fire material coverede over with carrdboard.

 

[Mike Johnson]

Modern housing use Dot and Dab for speed of construction it's all about cost, and let's face it very little skill required to slap a bit of plasterboard on a wall, all internal partition walls should be of brick/block construction so you can't hear someone burp in the next room, but again one less trade and speed of construction comes first.

 

[Deuce]

Most punters now days do not know the difference between dot and dab and traditional wall plastering, its only used in this modern age in very high end domestic building, the last one I was involved with at 67million had to import the plasterers from Poland to get the finish they required, the saving is in the time it takes to do a good job, as I said dot and dab in a day traditional takes many days.

I live in a 9 year old house on a typical modern housing estate. It's one of the larger houses but still just a 4 bed detached with detached double garage. It's just brick construction, not stone, nothing fancy. About 4 years ago we bought it for £365k. I think it originally sold for £230k but the town has picked up value quite a bit since then.

It has solid walls throughout, no stud walls at all and is fully wet plastered, no dot/dab anywhere - other than the extension I just added.

No idea why, it surprises everyone - myself included when I realised how quiet it is room to room and how easy it is to put up a shelf. But for whatever reason, some contemporary house builders for 'normal folk' still go this route.

I wonder if it might perhaps be that increasing claims for cracked skim finishes as the house bakes out for the first year has proven more costly to deal with than solid walls and solid plaster in the first place? I could see some house builders making that judgement. It's also probably not that expensive when you're putting up 200 houses to have a team of very skilled foreign plasterers (back then at least, pre brexit) enjoy a few years of gainful employment at a decent rate by their standards back at home.

I totally agree that Polish plasterers are fantastic. I too have worked in some incredibly expensive houses and I've seen them at work. A house next to Margaret Thatcher's old digs had a team in there that managed to finish a 4 storey stairwell and adjoining landings in fully polished plaster, seamlessly top to bottom, in less than a week. It looked like marble when they had finished - and it was, genuinely, flawless. Even the reflections across it were not distorted looking along the wall, it made me question whatever skill I previously thought my own two hands had to offer the world!!

 

[Mike Johnson]

Cracked skim finish's happen due to bad workmanship, either in the sub strata, plaster mix or insufficient time between coats, you never see cracks in polished plaster when applied correctly, most low to mid house builders are all about cost and maximising profit, and who can blame them for that, but it should not be too the detriment of the construction.

 

[Deuce]

Cracked skim finish's happen due to bad workmanship, either in the sub strata, plaster mix or insufficient time between coats, you never see cracks in polished plaster when applied correctly, most low to mid house builders are all about cost and maximising profit, and who can blame them for that, but it should not be too the detriment of the construction.

I was just making the point that a skim of plaster is more liable to crack over time, for whatever underlaying reason, compared to solid plaster.

Both can crack of course, but in my experience the 3mm skim is more liable to show hairline cracks than 15mm solid plaster.

 

[Mike Johnson]

It can of course, but not if its skimmed when the undercoat is still sufficiently damp that it takes in some of the plaster in the skim and forms an homogenous bond that dries out at the same rate as the undercoat, one of the biggest mistakes is plastering on a dried out wall so a bond does not happen.

 

[swaRRR]

Cracked skim finish's happen due to bad workmanship, either in the sub strata, plaster mix or insufficient time between coats, you never see cracks in polished plaster when applied correctly, most low to mid house builders are all about cost and maximising profit, and who can blame them for that, but it should not be too the detriment of the construction.

New build houses move when they settle and always experience cracking.

 

[Mike Johnson]

You may well believe this is the case, but new build houses move because they are inadequately constructed, as I have said earlier, I have been involved with some very high end housing and any cracking of the internal plaster would not be tolerated, unseasoned timber used in timber frames and internal walls, probably deck cargo brought over from, who knows where, during the drying process of this timber probably causes excessive movement and hence cracking, something the RICS, ARIBA, ICE and ISE have been putting forward as the reason for cracking in Court cases for quite a number of years. My flint stone house is over five hundred years old is built straight off a chalk strata bed and has no foundations and has not moved or cracked anywhere.

 

[westward10]

You may well believe this is the case, but new build houses move because they are inadequately constructed, timber framed and internal walls, all unseasoned timber and probably deck cargo brought over from, who knows where, the drying process of this timber causes excessive movement and hence cracking, something the RICS, ARIBA, ICE and ISE have been putting forward as the reason for cracking in Court cases for quite a number of years. My flint stone house is over five hundred years old is built straight off a chalk strata bed and has no foundations and has not moved or cracked anywhere.

How do you know it hasn't moved in its 500 year history. It could have suffered several movements of which you have no record of.

 

[Mike Johnson]

I think I would have seen this by the out of line or plum walls, even when the front to the house was blown off during the second would war the rest of the house including the 9M floor beams survived, external corners are still plumb and are of the very small hand made bricks of the original vintage.

And a certain 90 year old farmer and family that have been in the area since year dot, that have intimate knowledge of when the houses where built for and by the farm hands, it was built as two cottages and converted into one in 1957.