Dot and Dab vs adhesive for insulated plasterboard

[Oz07]

If you can afford to loose a couple of inch a metal jumbo stud infront of the existing wall would be cleanest and easiest. Not sure how it performs db wise but I'd imagine well as have seen it on plant of building conversions to flats. @nod?

[AliG]

I could do that or even just overboard it, but as the space would still be behind it where the sound reverberates and as anything will require moving the sockets back to being level, taking off the skirting etc, it seemed that unless there is a way to fix it in situ, we may as well take it off and replace it.

 

I also wanted to warn people of the noise risk as it was not obvious to me at all that this would be an issue.

 

The outside walls are pretty well sealed so the cold air getting behind has not been an issue. I did find it in a couple of places and fixed it with a squirt of foam.

Edited June 7, 2020 by AliG

[nod]

On 18/10/2016 at 20:00, AliG said:

Currently my house is specified using dot and dab to attach insulated plasterboard to the inside of the Porotherm inner leaf. The inner leaf will be plastered first with a parge coat so air behind the plasterboard shouldn't be much of an issue.

 

I would prefer mechanical attachment with the plasterboard hard against the blocks, but the contractor reckons Porotherm is too awkward for the number of fixings required. You cannot use standard fixings as the blocks are hollow.

 

Yesterday I came across Insta Stik which is adhesive for plasterboard instead of dot and dab. This would reduce the space behind the boards and maybe allow me to increase the thickness. It is also put on in lines instead of dabs so reduces the possibility of air moving about behind the boards. I then read up on the stuff and there are some people who think it is great and some people who swear by dot and dab as it is easier to move the boards around and get the walls flat.

 

The plasterboard will be skimmed so it doesn't have to be perfectly flat.

 

Has anyone used this stuff and got any thoughts? 
 

Keep the Parge flat and run a line of fire sealant around the perimeter and then every 200

and use the N Plugs  shown every 300 

The ones I have here are the smallest 80s you will need 150s 

We often cover large areas on offices etc where the plaster is sound but the walls require insulation 

[AliG]

So basically replace the plasterboard by using Insta Stik instead of dot and dab?

 

I did wonder this would fix the problem as the Insta Stik is put on in lines so there is less space for the sound to reverberate?

[Wil]

Holy thread resurrection...

 

If I had an old house full of dot and dab standard plasterboard onto solid stone walls, how would I go about improving the insulation? Do I have to tear all the dot and dab off and start again? It's all in good condition so would seem a waste.

 

I could drill the holes at head and foot of each wall and go nuts with the spray foam (form gun or the nozzle type cans?) but this would only stop air movement behind rather than improving insulation. Can I insulate direct on top of the existing dot and dab plasterboard? 

 

Thanks!

[Mr Punter]

9 minutes ago, Wil said:

If I had an old house full of dot and dab standard plasterboard onto solid stone walls, how would I go about improving the insulation? Do I have to tear all the dot and dab off and start again? It's all in good condition so would seem a waste.

 

Yes, remove it.  It is not a waste as all it is doing is taking space where your internal insulation should be.

 

You could of course have external insulation but this may not be aesthetically acceptable on stone walls.

[markc]

As above,  you will be surprised how much space can be taken up by old d&d.

[Wil]

Thanks both. External is definitely out thanks to the looks of the place, so internal my only option. Just going to be another horrific job to strip it out and then stud walls inside around a 300m2 place with lots of fireplaces etc.

 

Is there nothing that can be done over the top? If the air movement behind can be dealt with? 

 

Thanks

[AliG]

I would strip it off and replace it as otherwise you are going to lose quite a lot of space.

 

I don't see any benefit of putting it onto studs if that is your plan, this would still create an air gap as well as wasting space. Or is the plant to put insulation between the studs and plasterboard on the front? I would use insulated board as it loses the least space. If you run the numbers losing 100mm all the way round your house is a big percentage of the floor area.

 

In an ideal world you would strip back the plasterboard and try to make the walls behind as airtight as possible. If they are airtight, dot and dab or Insta Stik would work fine. If not you will have issues with air movement. In this case, I think @Nickfromwales method of sealing the top and bottom of the boards is best. I did suggest this to the builder but was told it was not needed as it was airtight behind the boards!

 

 

[Wil]

2 hours ago, AliG said:

 

 

I don't see any benefit of putting it onto studs if that is your plan, this would still create an air gap as well as wasting space. Or is the plant to put insulation between the studs and plasterboard on the front? I would use insulated board as it loses the least space. If you run the numbers losing 100mm all the way round your house is a big percentage of the floor area.

 

 

Yeh, I thought the 'right way' to do this was to go for metal (or timber) studs filled with insulation, then a VCL, then PB then skim (in order wall to room). But if I can 'get away with just gluing insulated plasterboard on, that might well be easier. Still going to be about 100mm minus the depth of my existing dot and dab out of the room all the way around though ?

 

I can feel the breeze moving around in some spaces and particularly floor voids when the wind blows, so under no illusions that it's air-tight behind! Would there be any benefit to me going with insulated lime plasters directly onto the stone walls (internally) to avoid condensation issues?

 

Does the insulated PB then need skimmed as well?

[AliG]

Plastering the walls would certainly help with airtightness. I don’t know how good insulated plaster is in practice. Can’t imagine it’s anywhere near the performance of PIR.

 

Skimming the plasterboard would only be necessary if you like the finish. You can just tape and fill otherwise.

 

However, a suspended timber floor is awful for airtightness and presumably has no insulation under it. Do you plan to take up the floor too?

 

I am no expert on stone walls, however as I understand it from older houses in Edinburgh often it is only heating the inside of the house that stops water making its way right through the walls from the outside. They tend to be sandstone which may be the issue. If you insulate the inside of a non cavity walk I am not sure what measures have to be taken to avoid water damage. Hopefully someone can help you with that.

 

 

[markocosic]

You can also 'EWI' the inside.

 

- hack back to bare stone 

- parge coat to air seal 

- dot and dab large EPS boards on 

- mesh 

- render 

- skim 

 

Works well even without parge coat if you seal the EPS gaps incl sockets etc with foam. At the time EPS and mesh/render was cheaper than insulated plasterboard and the external wall insulators were looking for work over winter so the labour was comparable.

 

Needs a good vacuum cleaner when they take the 8 foot rasp to the walls to plumb the freshly applied EPS though! ?

 

[Wil]

Mark- hah! that sounds pretty epic. And messy.

 

How does one fix things to the walls- will the EPS take a fixing for pictures etc? 

 

AliG- I meant the first floor suspended floor void, but yes, wher eI have a suspended ground floor, I'll also be taking up and insulating under/ between.

[markocosic]

The render takes picture hooks etc 

 

Long screws and wall plugs for anything super heavy. Angle them upwards to form a triangle (screw in tension and EPS in compression) for extra strength.

 

To be fair we have almost nothing attached to these walls though.

 

Of course now that enough grandmas have died they're renovating the whole block with ewi and new radiator pipework etc just too annoy us! ?

 

 

 

 

[markocosic]

Surface ends up about 4 mm render then 3 mm plaster on top of that. (the soft white stuff not the hard pink stuff)

 

Compared with dot and dab then skim there's no chance of getting hairline cracks between boards. It's quite tough yet flexible and basically had scrim tape/mesh...everywhere.

 

Waiting on new windows in this shot:

 

[TonyT]

Don’t let the builder dictate how you want it done after you have researched it, cause 90% of the time his method will be a shortcut to save him time, effort or materials or a combination of all 3.

 

At work  I insist that walls/floors are inspected prior to a covering/plasterboard being applied to ensure no shortcuts.

 

[Wil]

Interesting development in that I appear not to have dot and dab at all. I thought the hollow sections indicated dot and dab, but it appears I have solid plaster direct onto the stonework. Possibly with a thin skim coat of more modern plaster on top.

 

I bashed 7 bells out of a wall I'm going to drop anyway and it was fairly old plaster attached. I could potentially take other walls back too, but stripping all the internal walls back and re-insulating is a 'move out and live in the chicken shed type job'...

 

Does this change things in terms of removing existing though? Would that count as my parge coat in Marc's list above and I can then DnD EPS directly onto this?

 

The plaster appears to be up to an inch thick in places, no current signs of any condensation issues etc and I'd hopefully continue to avoid these!

 

I've attached a couple of photos showing some of the buildups where I've got back to stonework in case they're of any use...

 

 

[Mr Punter]

It looks like render and set.

[Wil]

1 hour ago, Mr Punter said:

It looks like render and set.

Thanks, is there any impact from this on means of insulating the walls internally?

[Mr Punter]

If it is sound I would leave it on and go over it.  Sometimes with old walls if you hack of the plaster you find big chunks of wall want to fall out.