Fixing Plasterboard to Cavity Block Wall

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maddad

Registered User
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Hi,

Once again I need to dip into the fountain of knowledge that is AAM!
I'm planning to dryline inside 1st floor bedroom wall. Wall is 9" cavity block and room is very cold. I am going to use insulation backed plasterboard of approx 40mm in total to reduce effect on room(Built in wardrobes to external wall etc). My questions are

1. Can I fix these boards direct to the wall with some sort of hammer in fixings. I don't want to batton wall if possible or use adhesive.
2. If I can fix direct to the wall do I use foil backed board or is vapour barrier required (Plastic Sheet etc)

I intend on completing job myself including plastering and just need to be clear on the right way to proceed.

Thanks,
Maddad
 
There are special long white fittings (possible name is mushroom fittings) that are used to secure insulated backed plasterboard to walls. The only problem is that you must get the correct size. When you drill through the plaster slab and the wall you will (most of the time) hit the cavity in the block. The fitting has to hold in that small hole in the block. The mushroom fittings are really designed for solid blocks.

Using bonding adhesive is the way to go though.
 
As regards no2 ...... insulation board is sufficient. As the earlier poster said, use plastic mushrooms or blob them on. If the latter, cut and measure all boards first, mark out joints, mix adhesive, fix boards onto wall and only when they are all in place ...... tap them level with a straight edge. Should be ready to scrim and skim after six hours.
 
If daub fixing, make sure to create a continuous bond at all junctions, ie at wall / floor level, at wall / ceiling level and at all opes. This creates trapped air pockets which aid in the insulation value of the construction, plus it negates the risk of 'thermal looping' which occurs if you dont do this....
 
sydthebeat said:
If daub fixing, make sure to create a continuous bond at all junctions, ie at wall / floor level, at wall / ceiling level and at all opes.
Click to expand...

syd, by this do you mean to "tape" all the edges? And thereby effectively create a seal to prevent any cooler air from behind the slabs mixing with the warmer air of the room?
 
Something along these lines (from Gyproc's website)

[broken link removed]
 
bobby04 said:
syd, by this do you mean to "tape" all the edges? And thereby effectively create a seal to prevent any cooler air from behind the slabs mixing with the warmer air of the room?
Click to expand...

no bobby, taping should be done as a matter of course.

What im talking about is the 'blobbing' of the adhesive on the boards.
Most builders just blob 6 or 8 blobs intermittently over the board and stick it up. This is a bad practice. This creates an air cavity behind the boards thats ventilated at junctions such as floors and ceilings.... this ventilated cavity exhausts at bad detailed points such as window boards, jambs, heads etc. This procedure is called 'thermal looping'... basically warm air is exhausted out and the replacement air has to be heated thus inefficient and extra heating etc. It also reduces air tightness.

if a continuous adhesive bond is created all along the boards where they meet the floors ceilings opes etc, this stops this phenomenon. it also increases the practical insulation properties of the construction as insulation is basically trapped air, which is what you are looking to create.. ie pockets of trapped air. This is a simple example of how better building practices can make a difference to energy efficiency.
 
Thanks syd, gotcha. Crikey the more I learn, and read experiences here, the more I realise how ignorant or just plain lazy (or both) so many tradesmen are. I just know my builder would have told me to do the slabbing myself if I'd explained this! How the hell are we ever going to move towards really energy efficient housing here when builders don't put in the effort with details such as this.
 
hire a relevant professional to ensure all these details are done correctly.

Ive always argued that a 'clerk of works' should be assigned to every building job, by law..... but that will never happen.
 
One point...dont dab the board , dab the wall and stick the board to this and use drywall compound and not bonding.....well two points actually!
 
Hi all.

I am going to fix my 50mm insulated board to the external wall with mushrooms. However I cannot locate the mushrooms on the web.
Anyone got a correct name for them. In the case of thes you drill through the board and into the wall. Then hammer these in. They have wide plate type heads to prevent the plasterboard pulling through. Whats there name and who supplies them.

Thanks
 
Brookes or Energy Savers do a good deal on plastic mushrooms.
 
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