AliG

Dot and Dab vs adhesive for insulated plasterboard

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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?

Edited by AliG
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There are a good number of critics of dotndab on this type of forum because of issues with airtightness. But, actually if done properly that's not as big an issue as claimed IMHO. As someone said on another thread this week airtightness is a sum of parts and an attention to detail across a number of areas.

 

I for one like dotndab and I side with your contractor that it is forgiving to uneven walls etc etc. It's quick, efficient and effective. 

Its also proven and works! I would say that ive not used the low expanding sticky foam but I can only beleive it is less forgiving. 

 

I would let your contractor use the method he's familiar with and just ensure it's applied properly and not bodged or corners cut. But that advise applies to any system.

 

just my 2p's worth! 

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Have you priced up the difference in a scratch coat and then skim against a parge coat, plasterboard and foam/adhesive and then skim.

Plasterboard has to be pretty flat as you can only take out 1-2mm with bonding and finish.

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I agree with Declan, If you are going to parge coat it you may as well scratch and skim that, I have used both and D+D is definitely better for taking out undulations, Foam is probably easier for a DIY job but the wall does need to be flat in the first place, I found it to be very messy but that may just be the way we were using it.

 

Edit: forgot about the insulation,....... how many walls are you doing?, might be worth getting a can or 2 of foam and letting the contractor have a go with it, see how he feels about it after trying it on a short wall.

Edited by Construction Channel

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It probably would be cheaper to plaster the walls rather than dry line, but the I like the extra insulation from the insulated plasterboard as it helps if there are any issues with the insulation in the cavity.

 

The skim coat on the plasterboard is definitely an extra expense, but it gives a much nicer finish. I recently had a ceiling fixed and skimmed versus all the other walls in my current house which are taped. It looks immaculate whereas I can often make out the joins especially in taped ceilings.

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22 minutes ago, AliG said:

 

The skim coat on the plasterboard is definitely an extra expense, but it gives a much nicer finish. I recently had a ceiling fixed and skimmed versus all the other walls in my current house which are taped. It looks immaculate whereas I can often make out the joins especially in taped ceilings.

 

Dry lined walls are the work of the devil. Maybe I've just been unlucky but I've never seen one that I'm impressed with.

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Dry lining is just a quick and maybe cheaper way of getting a wall finished. Most builders don't parge or scratch coat so Save here. Plus the boards gets generally stuck with a few dabs of bonding so as cheap as you get. Then a decent labourer/ painter can tape fill and sand the joins so Save on skiming materials and the labour bill of a Plasterer.

If it's my own house then it would always get skimmed. Lasts longer and looks far far better.

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I regularly use both methods Albeit we normally use gypsum acoustic tube adhesive with knock in fixings The problem with this method is the surface needs to be flat Not ideal if you are going over electrical capping's pipes etc. If your contractor dabs the walls and runs a continuous line of dry wall adhesive along the ceiling skirting line and each angle Head reveals and not forgetting to encase all switches  and sockets You should achieve perfect air tightness

 

 

 

 

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How will you stop air and wind from outside, in the loft and in the floor void from blowing around behind the linings?

 

if it does this then the insulation value of the protherm will be partly or totally lost 

 

don't underestimate how difficult it is to keep draughts out, lots of people get then coming out of socket outlets even on internal walls, under skirtings etc

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6 minutes ago, tonyshouse said:

How will you stop air and wind from outside, in the loft and in the floor void from blowing around behind the linings?

 

if it does this then the insulation value of the protherm will be partly or totally lost 

 

don't underestimate how difficult it is to keep draughty out, lots of people get then coming out of socket outlets even on internal walls, under skirtings etc

ou would be surprised how tuff it is to pass an air tightness test on commercial buildings

We build internal and external partitions out of MF studding and make up baffles to house all socket and switches

Party walls between flats are often built this way  rather than block As it is much easier to sound proof

with this system and achieve perfect air tightness As most are fire breaks and need to be totally air tight

Achieving air tightness on a house is quite easy

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We used inst stick in our SIP house. We stuck a 50mm insulation board to the inner skin, then two layers of plaster board then skimmed.  the lower board being cut to accommodate the services.

It was a total DIY job and we found it easy to use. We even did the slopping roof where we made a frame to prop up each board for 30min while it set.

4 years on and still stuck

 

 

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1 hour ago, tonyshouse said:

How will you stop air and wind from outside, in the loft and in the floor void from blowing around behind the linings?

 

if it does this then the insulation value of the protherm will be partly or totally lost 

 

don't underestimate how difficult it is to keep draughty out, lots of people get then coming out of socket outlets even on internal walls, under skirtings etc

 

No floor void, concrete slab, then insulation, then screed.

 

Loft isn't ventilated, ventilation is above the sarking board. However, it will be necessary to make sure it is airtight where the eaves and walls meet. That detailing has not been specified.

 

The Porotherm blocks have a parge coat so should be pretty airtight and thus little air blowing behind the plasterboard. Theoretically it can cover the gap around windows etc, but I will be checking.

 

Sockets, pipework etc can be surface mounted on the Porotherm as between the dot and dab and insulated plasterboard we have 50mm, so should not breach the airtight layer. Although actually I have tried as much as possible to have no services in the outside walls. Outside walls are a reasonably small percentage of the wall area and I only need to put sockets on them in a few places. I originally thought this would et me plaster the outside walls but decided the extra layer of insulation was better.

 

I think this was discussed on Ebuild, I have literally never seen a new build in Scotland that wasn't just dry lined.

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Is the concrete slab wet insitu concrete with walls built on it not through it?

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Yes. There are strip foundations below the slab, matching up with the walls above, which then goes right across them and the internal leaf and internal walls will be built off this slab. There will then be insulation and screed on top of the slab.The slab is 200mm thick. The SE requested very heavy duty foundations, part of this is maybe due to the weight of the upper floors which are constructed from 200mm thick hollowcore concrete planks.

 

I did discuss using an insulated raft instead as this kind of slab does have cold bridges. But the general view I got from everyone involved was that the cold bridges were too small to care and that ground conditions made an insulated raft difficult and more expensive.

Edited by AliG

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Nice, no air leakage, depends on how well insulated the building is as to how bad the thermal bridges are.

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On my retrofits ( another 3 in the bag this week ) I always dab as normal but then go around the foot and head with high expansion foam, and loads of it. The head so convection heat travel is arrested, and the foot to help with the previous but to also beef the boards up a bit for skirting / knock-ability. 

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how do you get foam in heads if you're boarding upto ceiling?

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Through the crack or drill a series of holes

Edited by tonyshouse

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12 hours ago, tonyshouse said:

Through the crack or drill a series of holes

+ 1. 

On 19 October 2016 at 18:16, Oz07 said:

how do you get foam in heads if you're boarding upto ceiling?

Thought I'd replied to this, sorry. 
I drill holes the same size as the foam nozzle, 8-10" apart, and pump in the foam that way. I get some bits of gaffa tape to cover the holes immediately after withdrawing the foam gun to stop the foam from spewing back out and messing the board up.
After 20 mins or so, I remove the tape and clean off any foam that's proud, then just scrim prior to plastering ( or leave if your putting coving up afterwards ). 

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3 minutes ago, Nickfromwales said:

After 20 mins or so, I remove the tape and clean off any foam that's proud, then just scrim prior to plastering ( or leave if your putting coving up afterwards ). 

 

@Nickfromwales if you're putting coving up does it not make sense just to leave a gap at the top and fill it ..?

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Suppose low expansion would be key to it working well. Wouldn't want to come back to a wall for all the boards to be 10mm out at the top!

 

when doing a ribbon bead I genuinely find that the gear fills up the space

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19 minutes ago, PeterW said:

 

@Nickfromwales if you're putting coving up does it not make sense just to leave a gap at the top and fill it ..?

All depends if that means a shed load of filling. The bigger the gap the more filling you'll have to do, plus the foam is a bit uncontrolled if it's open to the room. Remember that coving is 80mm or so from lip to internal corner and 30odd mm of that is for the adhesive to land so you've got 50mm to play with. I don't like the plasterer having to start or finish a set that close to where it's visible as they always get a bit of a bell at the top and bottom of the set. ( bless them ). Plasterers also hate the foam as if they catch it with the trowel it gets into the mix and upsets them. The less foam on display the less it needs cutting back and the less loose bits to get in the plaster. ;)  

Also, sometimes on a retrofit I've had to get the walls on prior to the ceilings going up, just to get things on and drying if we can't get the ceiling a up for any reason, so the foam option really does help out there. 

14 minutes ago, Oz07 said:

when doing a ribbon bead I genuinely find that the gear fills up the space

Yes, but there are dabbers, and then there are guys who have seen it done and have a go ;)  Prudence, and attention to detail are your friend, but a guy getting paid on meterage will always want to compromise that for a buck I've found. 

23 minutes ago, Oz07 said:

Suppose low expansion would be key to it working well. Wouldn't want to come back to a wall for all the boards to be 10mm out at the top!

When the dab has gone off the boards won't move one bit, if dabbed properly. I use high expansion foam at frequent intervals to ensure the gaps are filled. LE foam hardly expands at all so I don't recommend it for this tbh. Just don't go mad with it. 

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So it's not just here that plasterers don't like to bend or stretch. 

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Just resurrecting this thread.

 

The builders used dot and dab for all our plasterboard and for the most part it is fine.

 

On the outside walls they have used dot and dab to attach insulated plasterboard to our Porotherm blocks and there are no issues there.

 

On most of the inside walls there are also no issues.

 

But the wall between our gym and lounge is Porotherm block with dot and dab plasterboard on each side.

 

I created another thread where I noted that the door frames were not filled all the way round and I though this was letting noise through the wall. I have filled around the facings and it is maybe slightly better. But still sometimes if you are in the lounge and someone is talking or playing music in the gym it barely sounds like there is a wall between you at all.

 

Searching on Google I found that dot and dab is actually really bad for noise as it creates a solid path for noise to travel in the wall and a small air space to amplify it. Some people suggested that a wall will actually be less noisy with no plasterboard on it at all. I had assumed a block wall with a layer of plasterboard on each side would be better than a plasterboard wall from a sound proofing perspective.

 

Luckily this is the only sold partition in the house constructed this way without a door in it, so it is by far the most noticeable.

 

I am considering should I have the plasterboard removed and have the wall plastered instead or  is there an easier solution? There are also some pipes through the wall above the ceiling and there are sockets in the plasterboard on each side creating further noise paths. But when I try and listen it sounds like the noise is coming straight through the wall not in any localised spot.

 

Anyway let this be a warning that dot and dab is an quick and easy way to plasterboard a wall but bad from the perspective of soundproofing.

Edited by AliG

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Yes, dead naff. It causes a lot of thermal bypass if outdoor air can get in between the walls and linings. Draughts come out everywhere, you loose the thermal buffering of the masonry. 

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