Dot Dab with IWI

[Gaf]

@nod  Out of curiosity, when you mentioned not needing the parge coat, is that anything to do with needing to allow some external air to get in behind the sealed plasterboard to allow any moisture to move outward (externally)? Is there a risk of trapping moisture if there is a parge coat and then fully sealed plasterboard over that?

[Gaf]

1 minute ago, Iceverge said:

Those are K values and don't change with the thickness. You're stuck with what you have for a given material.

 

U values change with thickness alright. Thicker is a lower number which means less heat loss. 

 

What's in the 150mm cavity at the moment? 

 

 

 

 

Also what are your ultimate priorities here, room size, actually house performance or theoretical house performance? 

 

 

 

Currently EPS beads in cavity.

 

As it’s a new build I wanted my cake and wanted to eat it too. Now that the walls are up, I’m having to prioritise meeting building regulations for certification sign-off (wall u-value 0.18), followed by maintaining originally planned room sizes. Are building regs in the theoretical category? 

[nod]

6 hours ago, Gaf said:

@nod  Out of curiosity, when you mentioned not needing the parge coat, is that anything to do with needing to allow some external air to get in behind the sealed plasterboard to allow any moisture to move outward (externally)? Is there a risk of trapping moisture if there is a parge coat and then fully sealed plasterboard over that?

No 
Nothing to do with that 

years back We would parge everything Sand and cement then the more convenient bagged stuff (Sound coat) Mainly due to snotty block work

The block work would be so bad that you could climb up walls and see into cavities 

About 15 years ago All at once BC clamped down on this and Brickies where paid an extra £1 m2 to point and bar rub all joints 

The housing association jobs and commercial jobs carried on doing both for a couple of years 

But now only self builders do it 

It’s one of those things that came in when sites went from wet plaster base coat to dot and dab 

We still use it But for sound deadening 

As I’ve said on many occasions 

If you tell your dryliners that it’s for airtightness They won’t bother sealing anything 

 

 

[Gaf]

On 28/12/2024 at 21:32, nod said:

Every wall should look like this Real basic stuff 

 

Do you place a band of adhesive running down the wall where each board will meet (e.g. attached, pink lines)? Sealing behind each board? Or is it the bands of adhesive are just needed at the floor, ceiling, and wall junctions, and around fixings (sockets)?

[nod]

59 minutes ago, Gaf said:

 

Do you place a band of adhesive running down the wall where each board will meet (e.g. attached, pink lines)? Sealing behind each board? Or is it the bands of adhesive are just needed at the floor, ceiling, and wall junctions, and around fixings (sockets)?

No

Just the  perimeter 

[Gaf]

Final post on this (hopefully). Got a meeting on site. All very amicable. It was agreed to provide full sealant all around boards (ceiling, floors, walls, sockets) as per @nod’s way of doing it. 

 

Plasterer said he’s happy to have them all completely flush against walls (no void) but warned of potential issues with skirting having gaps if block work is slightly off in places. Blockwork look immaculate to me so tempted to go this route.

Edited yesterday at 18:23 by Gaf

[nod]

I’d tell to just do his job right Of course there will be voids There has to be at least 12.5 mil to get over the 25 mil back boxes 

 

Id be looking for another dry liner with a bit more experience if he thinks he’s doing a special job by sealing around the boards 

Edited yesterday at 18:49 by nod

[Gaf]

2 hours ago, nod said:

I’d tell to just do his job right Of course there will be voids There has to be at least 12.5 mil to get over the 25 mil back boxes 

 

Id be looking for another dry liner with a bit more experience if he thinks he’s doing a special job by sealing around the boards 

 

Boxes are partially chased. They checked measurements and flush to wall would just work.

 

Out of curiosity, if a parge coat has been added to the block work, then the plasterboard is added using the proper approach (sealed top bottom sides sockets etc), is there any risk of trapping moisture behind the boards?

Edited yesterday at 21:06 by Gaf

[joe90]

2 hours ago, Gaf said:

as per @nod’s way of doing it. 

As per the correct way of doing it 🤷‍♂️

[Gaf]

11 minutes ago, joe90 said:

As per the correct way of doing it 🤷‍♂️

 

I did have that written initially but wanted to acknowledge nod’s advice 👍

[nod]

12 hours ago, Gaf said:

 

I did have that written initially but wanted to acknowledge nod’s advice 👍

You will have a void behind the boards 

We tell kitchen fitters etc measuring prior to plaster To allow 30 on the top of the blocks for D&D