Batten or dot and dab

[Matt Morton]

So we are just starting first fix on our new build.  Construction is solar blocks with cavity (and 130mm PIR in cavity). external is a mix of wood cladding and flint blocks.

 

We are trying to achieve good airtightness levels (1-2?) (and we were I think pretty diligent in sealing the PIR at all joins with aluminium tape and foam where needed) - though not  aiming for passive house-  for MVHR system to be effective (and to make the most of the triple glazed window investment!).  

 

My main questions are:

1. do we need to parge coat the inside of the external blockwork walls

2. Is there a recommended preference between batten and plasterboard or dot and dab (do either route make airtightness easier to achieve) 

3. Is it better to wet skim the plasterboard on the external walls rather than just taping and filling joints - from an airtightness perspective.

 

Understand this is a somewhat well trod discussion path , but be interested in latest (and simplest ) thinking.

[Matt Morton]

[Iceverge]

Welcome to the forum.

 

I would suggest wet plaster. Or failing that a parge coat and a battened service cavity. (You can put more wool insulation in here too)

 

Dot and dab isn't a good idea for airtightness. 

 

The airtightness game is won or lost by the time you get to taping and jointing/skimming as the plasterboard will have so many top and bottom edges and holes it'll make no difference what you do. 

 

How much of a residual cavity have you left beside the PIR? I wouldn't be a great fan. I have 2 neighbours who filled the residual cavity with closed cell foam to some success. 

[Chanmenie]

Dot and dab is fine if done correctly with a continuous bead of adhesive all around the perimeter of each board, then wet plaster skim 

[Russell griffiths]

Why not get an airtest done before you plaster and see what your looking at. 
I did a test at watertight stage to see what I was missing. 

[nod]

7 hours ago, Matt Morton said:

So we are just starting first fix on our new build.  Construction is solar blocks with cavity (and 130mm PIR in cavity). external is a mix of wood cladding and flint blocks.

 

We are trying to achieve good airtightness levels (1-2?) (and we were I think pretty diligent in sealing the PIR at all joins with aluminium tape and foam where needed) - though not  aiming for passive house-  for MVHR system to be effective (and to make the most of the triple glazed window investment!).  

 

My main questions are:

1. do we need to parge coat the inside of the external blockwork walls

2. Is there a recommended preference between batten and plasterboard or dot and dab (do either route make airtightness easier to achieve) 

3. Is it better to wet skim the plasterboard on the external walls rather than just taping and filling joints - from an airtightness perspective.

 

Understand this is a somewhat well trod discussion path , but be interested in latest (and simplest ) thinking.

Fit and dab is fine When sealed properly 

Dont waste your money at Parge coat 

There’s only self builders that seem to bother with now 

Instead make sure the block work is properly pointed 

[Mike]

10 hours ago, Iceverge said:

I would suggest wet plaster.

Me too, for the quality of the finish as much as anything else (provided you find a good plasterer). However well dot & dab is done, you're guaranteed to see the joints in at least some lighting conditions.

[Nickfromwales]

45 minutes ago, Mike said:

However well dot & dab is done, you're guaranteed to see the joints in at least some lighting conditions.

That should read "tape & joint" aka dry-lined, as that doesn't have a wet plaster coat. Dot & dab is how the boards are affixed to the underlaying wall  and taped and filled joints are the ones always visible forever aka 'shart'.

 

I can recommend a fantastic plasterer in the Coventry and surrounding areas (he'll drive an hour or so). PM me for details.

[Mike]

3 minutes ago, Nickfromwales said:

Dot & dab is how the boards are affixed to the underlaying wall  and taped and filled joints are the ones always visible forever aka 'shart'

Spit on! I shouldn't rely to stuff at this time of the night...

[Nickfromwales]

1 hour ago, Mike said:

Spit on! I shouldn't rely to stuff at this time of the night...

No need to spit on it, just sand gently and paint 🤣

 

It's Saturday night ffs, and if anyone's posting here whilst sober I want their name, rank and number so they can get a proper bollocking.