I've read some comments that suggest dot and dab will affect the warmth/energy efficiency of a building due to drafts setting up behind the plaster board. Can anyone confirm if this is true?

I'm having some work done and I know the builder is intending to D&D, so now would be a good time to raise the issue with him if traditional platering would be better.

Thanks

Sean

You will also be isolating all the thermal mass in the wall from the room. Thermal mass helps to moderate the temperature in your house as is therefore useful so don't cover it up with plasterboards. A wet plastered wall gives a nice, solid feel to a house also I think.

Anyone with an opposite view?

Thanks for the responses.

I take on board your comments about D&D being crap. A friend has been trying to hang a shelf for the last week and has ended up with a six inch hole in the plasterboard (admittedly he's not very good at DIY!).

Now I've got to negotiate with the builder to do a 'proper' job! Can anyone give me a unit cost of D&D compared to a traditional plaster finish, say from SPONS? I imagine he will try and charge me more, so at least armed with that information I should be able to limit the financial damage.

Great Tony, thanks.

You are wrong! All except about the bit about it being cheaper that is!

Block-work is not air tight nor is cavity wall insulation.

In the UK we build some of the leakiest houses in the developed world ( some mud huts are more air-tight than our new houses )

Wait till you live in a new house where you have to leave all the plugs in the kitchen sockets because of the draughts.

You have a lot to learn still.

Oh yea and wet plastered walls are never left for two years before painting -- where did that come from?

2yrs!!!!! maybe for timber frame as you say Paul but not for masonry built in the UK. Also timber frame in the UK sometimes uses enginnered beams which are advertised as only having minimal shrinkage after installation. I've no doubt the shrinkage theory is right as I have touched on this but in reality you usually only get minor shrinkage cracking, and this can be alleviated by the use of cornices and skirtings. Lots of other factors as well, including heating regime

Paul, I've been plastering for more than twenty five years so have seen some variety of conditions. I've used all manner of renders and plasters on all manner of surfaces. I've used hessian, cotton skrim and fibatape on plaster board joints with varying levels of success. Have to agree to disagree.

I remember my old plastering teacher telling me about the development of cornice. He maintained that it was developed partly to hide shrinkage cracking which occurs as a result of materials having different levels of thermal expansion, ie ceiling joists and wet mortar. Skirtings were developed for similar reasons I believe

Posted By: Mike GeorgeI've used hessian, cotton skrim and fibatape on plaster board joints with varying levels of success. Have to agree to disagree.

That's OK - I was only partly teasing about cornices anyway.

Over here, everyone uses drywall/plasterboard/gyproc (different places use different names). Standard joint material is paper tape - at least amongst the pros - as it is cheap and effective. Fibatape is used more by neophytes as it sticks in place before the joint compound is applied but supposedly isn't as good as the paper tape. At the ceiling/wall joints, I use steel corners that are embedded in paper tape. These don't crack at all - but are much more expensive than paper tape - but as I'm not a pro and am essentially only doing 1 building, that's not a big deal.

When I was in the UK I did some some plastering, but we wallpapered on top rather than painted. I did recall at the time being advised not to use oil paint on fresh plaster (fresh being less than 1 year if I recall correctly). I think the lime needs access to CO2 to cure properly anyway and it takes some time.

As for skirtings, I believe the main reason is that the walls are plastered before the main flooring is installed so it's difficult to know exactly where to stop, plus, at least with wood flooring, an expansion gap is required which is neatly hidden by the skirting board.

Anyway, to get back on track, drywall is standard over here and we build homes airtight so blob-and-dob is not a problem per se- it's the structure behind that should be airtight in the first place. That said, blob-and-dob is not used here since the drywall is screwed either to battens or directly to the framing. In our new house, we have foil-faced foamboard on the framing (sealed with acoustic sealant for air and vapour tightness), then 1x3" strapping on top of that with the drywall screwed to the strapping. This is then finished with the standard tape and joint compound technique - though some people do skim coat instead (though this is very rare in residential construction).

Paul in Montreal.

Posted By: Mike GeorgeRe. Lime render. Maybe we are cross purposes here as I wasn't referring to lime render, which can take a long time to cure in our climate. I only use lime in combination with cement.

But standard plaster contains lime doesn't it? Or is it all just gypsum these days? I remember seeing a bucket of lime putty when I was a child watching some neighbouring houses being plastered.

Paul in Montreal.

Comment Author ; howdytom CommentTimeJan 12th 2008 quote from another thread on blob and bob

"We hauve to leave all our sockets with plugs in in the kitchen otherwise we get draughts coming out of them !!!.
tom.. in the wind north "

It wasn't me it was Tom


I could agree with you that an extra layer of entrapped air would increase the U value of a wall

(Masonry walls do not yet have any air-tightness layer or barrier in then, indeed we dont even know where to put one yet in traditional construction)

But what if the air is not trapped but connected to outside as is often the case? Then the only U value you have is that of the plasterboard itself.

Sadly this is often the case as can be surmised by the two recent ideas of firstly ribbons of adhesive and latterly of parging coats before sticking on plasterboard.

please remember that neither of these were happened during the 70's 80's or 90's and often still aren't done today either.

If block work is air permeable, then how thick would a lime/plaster coat need to be to make it air tight..... thoughts are; old house with draughty walls(limestone with lime plaster). want to install insulated plaster boards..... dot and dab!??. pointless insulating the outside of the walls as they are 700-900mm thick rubble infill and going by other posts would take a month to heat up(passive solar, heat travels app 1metre/month) if there was no air circulation within the walls (impossible to stop).
tom

I was thinking a bit about what was said with the wind traveling though behind the boards.
I then thought about the common method used now where batons are put in. If the batons where both vertical and horizontally placed very little air would travel behind them. I have seen examples where people have used the dot and dab method to fix the batons to the walls and then screwed or nailed the board to the batons.
When it comes to insulation the gap that is formed behind the board could be filled with a thin insulation, this could prove useful on a solid brick wall in older property.

Tony, I re-furbished and extended an old house 3-4 years a go. the original building is 2' thick stone, rendered outside, the new is block cavity. I Dot and dabed the whole thing (almost). Worked a treat. Quick, low cost, easy, little mess, no draughts, no settlement cracking,and better insulation than without (I have the odd external wall which was just skimmed and not dot and dabed and they are cool to the touch when compared with the dot and dabed walls) You have to be a bit sensible when fixing things to walls but once you know, this isn't a probem. Nearly all modern ceilings are now plasterboard and with a layer of insulation on the back and they have a lower U value than any other element of a house, I'm sure you wouldn't argue that we should make ceilings from blocks and then render them with an inch of cement and then skim!........... madness!

My work takes me to many commercial sites which are often quite large, some of them are rendered for maximum impact resistance and the cracks that appear as the building dries and settles are quite alarming, never seen any on a dot and dabed building!

Hundreds -- discontinuous anywhere, wind straight in from the cavity! through any service penetration, all over the place, from the party wall? from the garage?