Dot & dab dryline or conventional plaster

[dhutch]

Im assuming this has been done to death, but im actaully stuggling to find much, let alone a good debate about the pros/cons.

Almost all of my house (1940 council build) has been re plastered using PB and dot&dab which in the main works and is being left. No obvious signs of it having been conventionally plastered before. But im just wondering how common this is now conpaired to conventional (as per my parents house, 1980's build) and how durable it is.

Would the house have been conventionally plastered when new, and this removed before replastering?

The question stems from having gone to regrout some leaking tiles in the bathroom and ended up taking of the first foot of tiles and finding the bottom of the PB by the bath totally rotton.
Might bodge it for a bit, but in the long term the bath is going to have to come out i suspect and replaster and in wondering wheter to stick with dot and dab and just redo using cement board, or if to go to conventional plaster here.


Daniel

 

[peaps]

It's possible that the house was constructed with board. I suspect it was done with cardboard sandwich frame system. These are pre fabricated wall built with board front and back with card and wood frame in the middle. Many council houses were built using this system. If this is the case then you may have problems as the board can't be deconstructed easy to affect a standard repair. One other problem was that they didn't put finish on the walls, just taped, paper lined and painted.

If you dig at the damp area you will be able to see what construction method was used then we can advise accordingly.

Plasterboards was used back in the early 1900 and took off around 1920ish your house could be rendered or PB or even a mix of the two. The internal footprint was mainly PB and the outer walls render in some cases.

 

[dhutch]

I suspect it was done with cardboard sandwich frame system. These are pre fabricated wall built with board front and back with card and wood frame in the middle. Many council houses were built using this system.

Ok, that would make sense, thanks. In which case this has all been removed and replaced with dot & dab pb.
- Ive drilled 10mm holes through it in enough places to confirm this is the case.
- Origanally it was suggest that there was insulation behind the boards, which has proved not the be the case.
- IM going to get the house cavity walls filled with polystrine balls in a few weeks, a bodge, but not a bad one imo.


Daniel

 

[peaps]

I suspect it was done with cardboard sandwich frame system. These are pre fabricated wall built with board front and back with card and wood frame in the middle. Many council houses were built using this system.

Ok, that would make sense, thanks. In which case this has all been removed and replaced with dot & dab pb.
- Ive drilled 10mm holes through it in enough places to confirm this is the case.
- Origanally it was suggest that there was insulation behind the boards, which has proved not the be the case.
- IM going to get the house cavity walls filled with polystrine balls in a few weeks, a bodge, but not a bad one imo.


Daniel

I've seen this done and on the outside walls the dab became more of a cold spot and dripped constantly in the cold, more so than before the cavity was filled.

Worth thinking about.

 

[dhutch]

I've seen this done and on the outside walls the dab became more of a cold spot and dripped constantly in the cold, more so than before the cavity was filled.

I can see the dab being a cold-bridge between the relativly cold inner brickwork and the warm plasterboard+room but I cant see why it would get worse by insulating the cavity and hence increasing the temp of the inner skin?

Ive heard arguments that filling the cavity can increase damp by stoping air circulating in the cavity. But more online reading suggests they now use better insluation (ie, closed cell balls rather than rockwool or paperbased) and the issue isnt a huge one. The cavity vents are already silconed up.


Daniel

 

[peaps]

I've seen this done and on the outside walls the dab became more of a cold spot and dripped constantly in the cold, more so than before the cavity was filled.

I can see the dab being a cold-bridge between the relativly cold inner brickwork and the warm plasterboard+room but I cant see why it would get worse by insulating the cavity and hence increasing the temp of the inner skin?

Ive heard arguments that filling the cavity can increase damp by stoping air circulating in the cavity. But more online reading suggests they now use better insluation (ie, closed cell balls rather than rockwool or paperbased) and the issue isnt a huge one. The cavity vents are already silconed up.


Daniel

The surronding area is warmer..? And yes moisture can become higher. Choose your product with care.

 

[dhutch]

The surronding area is warmer..? And yes moisture can become higher. Choose your product with care.

Correct me if im wrong, but insulation between the two walls increases the temp diffrential. Hence assuming the air on the inside and outside stays largly the same, the inner wall becomes warmer, and the diffrence between the inner and the pb becomes less, making the temp more even and the cold spots let cold? Unless you increased the humidity in the house, and condensation on the pb would be reduced i would have thought.

Anyway, by the by, what product would you specify?

Having applied for the gov grant i have been allocated DG Insulation who have done a 'survay' (quick looks see into the cavity with a rigid borescope) said it looks dry, and said i can have standard round white EPS balls for £100 (£600 ish, less grant money) sprayed in with a binder, or for an extra £100 i can have pebble shaped carbon dust coated EPS balls, which nominally give a 10% inprovement of the std ones. But proberly equally critically look cool in the presention box and only cost £100 more!

Quite honestly, the comments i have read around the warn of damp do worry me a little, but as far as i can tell its few and far between.

Daniel

 

[peaps]

The surronding area is warmer..? And yes moisture can become higher. Choose your product with care.

Correct me if im wrong, but insulation between the two walls increases the temp diffrential. Hence assuming the air on the inside and outside stays largly the same, the inner wall becomes warmer, and the diffrence between the inner and the pb becomes less, making the temp more even and the cold spots let cold? Unless you increased the humidity in the house, and condensation on the pb would be reduced i would have thought.

Anyway, by the by, what product would you specify?

Having applied for the gov grant i have been allocated DG Insulation who have done a 'survay' (quick looks see into the cavity with a rigid borescope) said it looks dry, and said i can have standard round white EPS balls for £100 (£600 ish, less grant money) sprayed in with a binder, or for an extra £100 i can have pebble shaped carbon dust coated EPS balls, which nominally give a 10% inprovement of the std ones. But proberly equally critically look cool in the presention box and only cost £100 more!

Quite honestly, the comments i have read around the warn of damp do worry me a little, but as far as i can tell its few and far between.

Daniel

Depends if you are insulating the brick cavity or the PB cavity. I was refering to an instance where the PB cavity was insulated...

 

[dhutch]

Depends if you are insulating the brick cavity or the PB cavity. I was refering to an instance where the PB cavity was insulated...

Ahh right, that all makes sense now. I thought that we must be talking at crossed purposes or somthing like that.
But no, given its not done like that as it is, im not planning to add any insluation there, but have the cavity done as suggested.

The bathroom is going to bodged with offcuts of PB and drywall adheasive, get the tiles back on, grount it, try and keep the water out, and think about it later.


Daniel

 

[peaps]

Depends if you are insulating the brick cavity or the PB cavity. I was refering to an instance where the PB cavity was insulated...

Ahh right, that all makes sense now. I thought that we must be talking at crossed purposes or somthing like that.
But no, given its not done like that as it is, im not planning to add any insluation there, but have the cavity done as suggested.

The bathroom is going to bodged with offcuts of PB and drywall adheasive, get the tiles back on, grount it, try and keep the water out, and think about it later.


Daniel

The problem was that the brick had no cavity. I would slap a skim on the bathroom wall if you can. No need to be the best in the world as long as it's flat if you are to tile. I did a job for a friend who had a drip that was comming in through the tile when in the shower. Caused much damage because it was just a drip and soaked in the wall, floor and the kitchen ceiling, by this point it was too late and the damage was done. Them slow seeps are the worse.

 

[dhutch]

Yeah, it certainly not done the PB around the bath any favours. Ive only been in the house a few months, but its clearly been doing it for years, and been bodged once before be sticking a few troublesome tiles in with a big gob of silicon.

I think my plan for now is to hack out anothe 4inchs or so of the mess by which time i think it will be fiarly hard given how it firms up on what ive seen and take out the damp PB under the bath. Then just patch with PB, dont and dab, buttering the joint up a bit with left over drywall adhesive, get the tiles on (laying them in induvidual 2inch tiles) and keep and eye on it.

Its only a long weekends work to have the bathout, PB of, cementboard up, seal, bath back, and tile. But i just dont have a weekend between now and january and with two lodgers i cant have polytheine tapped over the jab for three months.