utility room stud wall detail.

12 Feb 2014
Reaction score
United Kingdom
Morning all,

Have just started to prep for converting a 3m x 3m section of the garage into a utility room,

So far I've laid a row of bricks to raise the floor level eventually and for the sole plate and Dpc to sit on for the stud wall.

I can't find a clear illustration for the setup of the stud wall. I'm going for a floating floor so this will be laid on a Dpm.

Do I lap the floor Dpm over the course of brickwork and then fit a dpc aswell before the timber sole plate goes on?

I'm going for 25mm celotex on the warm side with taped joints and 80mm between the studs as this would make a VCL from what I've read. Does the breathable membrane go on cold side and do I have to lap this under the soleplate aswell? If so between which layer?

With regards to securing the stud wall, am I best to avoid fixing into the external double brick wall of the garage to avoid damp and would it be wise to fit a vertical dpc in here aswell?

Sponsored Links


No VCL, foil tape internal celotex, no breather membrane, vDPC between stud frame and garage wall.
Morning Woody and thanks as always for the info. Is that from the nhbc website? I can never find the right illustrations.

I've got a 115mm drop into the garage so have raised the floor one brick (not engineering though). Going to make a sort of bund for the floating floor to leave an air gap when I put the new stud wall up against the single skin walls. Guessing this will be ok.

I've got 4 x 2 studding, so 89mm finish and was going for 80mm PIR so would that put me back into the breathable membrane situation? 25mm PIR on the front taped to make a VCL.

Sponsored Links
The drawing is from my hard drive, so you wouldn't have found it.

You don't need a breather membrane. There should be no gap between the two pieces of insulation, the gap can be on the back. You may find that your 4x2 is actually more like 94mm anyway.

I don't understand the bit about a "bund" for the floor, but there should be no air gap in the floor
Ah, yeah I don't have access to that! The hard drive of knowledge!

Just checked the timber, I've ordered CLS so it shouldn't be too big a gap behind anyway.

Here's what I'm playing with,

IMG_20210211_101014.jpg IMG_20210211_101024.jpgIMG_20210211_101039.jpg IMG_20210211_101150.jpg

The damp is coming through below the dpc on the wall closest to the neighbors. My plan is to lay engineering bricks 50mm in from the wall to form a perimeter to stop any moisture getting at the new walls. Then line the new area with a Dpm and fit the PIR in tight for the new floor.

There's a 1ft gap between us and the neighbors and their property is 2ft higher than ours. The ground level between is level with our concrete floor.

The boiler wall was lined with PIR board between studs about 7 years ago but there's no DPC between the studs and brickwork. I'd love a workaround for this that doesn't involve taking the boiler off the wall and starting again with a new wall.

Well if you do it like the drawing and DPM around the utility floor, than that should do it.

Presumably the damp coming across that garage wall is not at a higher level than your new utility floor level. Otherwise you'll need to take the DPM upstand further up the wall
Yep will do, with mine being a floating floor I was thinking.
  • thin layer of sand to level out floor
  • Dpm
  • 80mm PIR, taped
  • T&G moisture resistant chipboard
  • Hardie backer And tile finish.
Would that make the dpc laid across the concrete in the illustration my slip layer? To go between the PIR and chipboard?

Looks like I don't need a strip of dpc under the soleplate.

The damp will be higher than the floor level, would tanking the walls below the dpc make any difference? I'll leave the floor Dpm higher definitely.

Any thoughts on the boiler wall, do I need to start again?

appreciate your help. Thanks
Last edited:
Afternoon Woody,

Just ordering the Dpm to make a start this week,

Could do with your wisdom on the last post regarding the slip layer, tanking and boiler wall.

Would the slip layer be the same material as the Dpm?

Afternoon, from what I'm gathering the slip layer has to be 500 gauge polythene according to kingspans floating floor build up.

With regards to the damp is there anything I can do about this? Or just lay the new bricks and ignore?
I don't specify slip layers as they are unnecessary. Just use DPM as per that image.

The image shows the principle to apply to seal the new room from any dampness. If walls are susceptible to dampness then a DPM will need to be taken up the wall too and lapped and sealed with the floor DPM.
Ok I'll leave the slip layer out.

So my floating floor DMP will ride over the one course of bricks, back to original floor level and then continue up past the courses of blues. Thinking I can lay a piece of vertical dpc (400mm ish) around the outside wall perimeter and then the Dpm will lap this?

Can I leave the boiler wall as is or am I asking for trouble with the building inspector or damp in the future.

Thanks for your help.

You'll have to get the building inspector's advice on how to treat or adapt the wall behind the boiler. Strictly is should be treated the same as other walls if it's external, but there may be options.
I'll give him a ring, better to do it now than have to take the wall apart afterwards.

For the rear wall with the door and window I was thinking, screw battens to vertical dpc and then stud and insulate between with 75mm, and top with 25mm PIR to meet regs. Guessing I could make this into a floating wall and not have to lay a course of bricks for it to sit on?


DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links