Dormer Draught Problem

The_Bag

Hi everyone.

I'm in the process of revamping a 60's 3 bedroom dormer style semi.

I've had it rewired & a new central heating system fitted so all the carpets have been lifted upstairs as well as some floorboards. I've noticed that the draughts are bad under the upstairs windows at floor level. On further inspection I've noticed that where the upstairs floor void meets the two course external wall (dwarf) & the stud wall under the windows there is in some places two courses of bricks missing?? When the the wind blows you can feel it coming in through this gap very bad.

After reading a forum http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=697 I've started to wedge Rockwool insulation into the floor voids between the joists so that it's wedged between the joists, the downstairs ceiling, & the underside of the floorboards.

This seems to stop most of the draughts but I'm worried that it may cause problems later on as it may cause condensation if you block it off completely or is the Rockwool breathable enough to stop this?? At the rear of the house there's two airbricks where the internal soil pipe goes from the upstairs bathroom to the sewer system.

Any help will be a great thanks.

iamcornholio

There is no problem with sealing air gaps in floor and wall voids - current building practice actually requires it

The_Bag

I still can't beleive the size of some of the gaps in the floor void where the joists meet the external dwarf wall. I thought that maybe they were deliberately left there to ventilate the floor void??

By wedging the Rockwool into the gaps stops most of the draughts for now but has anyone got a better suggestion how to do this for the long term. I've had all the bedrooms redecorated so are reluctant to start taking plaster board down from the inside the property but could I insulate the dormers from the outside if I removed the soffits from the outside??

Thanks.

The_Bag

Does anyone have any previous knowledge/experience with my problem please??

I was thinking of getting a builder to see if it would be possible for them to remove the soffits & then add the missing bricks from the dwarf wall up to the stud wall, & try to make the upstairs floor void airtight. The distance between the joists is about 16" in most places so I'm not sure if it would be possible or not.

Any help with this would be great thanks.

The_Bag

Any help would be great thanks :beer:

iamcornholio

I think you need to clarify what you want to do.

The thread title relates to "Dormer Draught Problem", but your other posts mention floor voids, dwarf walls, stud walls and then insulating dormers by taking soffits out.

Dormers are the bits that stick up out of a roof and so are not accessible via soffits

The_Bag

Oops! :eek:

Ok thanks. As you can probably tell I'm no expert in this field & only a amateur as this is my first house I've owned.

What I would like to do is find out the best way to fix the problem with the floor void? What I've done is better than it was but I can only get access to the 3 bedroom floor voids so the bathroom is leaking air terrible. This brings me back to my last post in saying would taking the soffits off would a builder be able to replace the missing bricks & then hopefully cure it for good??

Thanks again & sorry for the confusion.

lesalanos

Hi,

I have the same problems as you with big gaps at the top of the walls. So far I have insulated the edges of the rooms. I was luckiy in that the floorbaords had aready been up and so I could lift them again and fill the gaps. I squirted some expanding foam into the bits that I could not reach. This has stopped a lot of the draughts, before you could feel the draughts through the floorbards in the middle of the bedrooms.

I still have some work to do as there are still some draughts that I noticed when changing a light switch. I am also looking at removing the soffit baords and doing something here to block the holes.

Good luck in sorting it out.

The_Bag

lesalanos wrote: »

Hi,

I have the same problems as you with big gaps at the top of the walls. So far I have insulated the edges of the rooms. I was luckiy in that the floorbaords had aready been up and so I could lift them again and fill the gaps. I squirted some expanding foam into the bits that I could not reach. This has stopped a lot of the draughts, before you could feel the draughts through the floorbards in the middle of the bedrooms.

I still have some work to do as there are still some draughts that I noticed when changing a light switch. I am also looking at removing the soffit baords and doing something here to block the holes.


Good luck in sorting it out.

Thanks, but as I posted before in some places where I could see there is two courses of bricks missing below the stud wall. What also made it more difficult is that the central heating pipes run just in front of the gaps so trying to wedge Rockwool in just in front of the missing bricks was difficult as I didn't want to disturb the pipes.