Drafty suspended wooden floor void upstairs (1st floor)

[myk3]

Hi there,

I have a 1930s semi-detached house which i recently purchased. I have discovered that there is a draft in the 1st floor/ground floor ceiling void which can make the floor cold and also draft up into the rooms from the skirting.

This house has solid brick work so is not the drafts from where the joists go into the inner leaf (like a house with cavity walls would).

The house has 2 single story extensions on ground floor and a small bay window with a roof. no doubt there is a draft from one of these entrances...

I want to close off all drafts by doing the following:

1. Pull back the carpet at all external walls upstairs and lift 1 or 2 floor boards.
2. Seal with silicone or expanding foam any locations i can see gaps in the brick work like cables etc that will run into the roof of the single story extensions.
3. Cut 50mm Celotex board to size and butt it between the joists so that it creates a "plug" betwean the ground floor ceiling and the 1st floor floorbard closest to the wall.
4. Seal around this celotex board to close any small gaps.
5. Lay hardboard on top and caulk the bottom of the skirting to it to create a seal.

My only worry about doing this is ventilation to the 1st floor joists. as this will block all air circulation to the very ends of the joists i worry that this could potentially rot them over the years and thus cause huge damage.

Any advise on this would be most appreciated as the drafts are rather annoying and not letting the rooms upstairs efficiently hold the heat for as long as they should.

thanks,

Mike

 

[dishman]

Have you not posted this same question about 3 to 4 times in the last month or so?

//www.diynot.com/forums/buildi...suspended-timber-floor-above-bathroom.386561/

//www.diynot.com/forums/buildi...of-entering-ground-floor-ceiling-void.386608/

//www.diynot.com/forums/buildi...nded-wooden-floor-semi-detached-house.388992/

Is there question you don't feel has been answered?

 

[myk3]

Yes but and they have been answered. For example i have put the floor insulation above the bathroom. I used 10cm thick insulation and thus there is still a ~6cm gap in the void above and all cables sit on top of the insulation and thus air can still pass.

my main issue and question i have not got an answer to is about blocking off the air circulation towards the external walls at the perimeter of the 1st floor.

I just need to know if doing this could potentially rot the joists as this will be an air tight seal.

sorry for re-posting but i never got an answer to this in my last thread so thought a new thread focusing on this would help...

 

[dishman]

As I said, in my previous post, what is your ultimate aim, why are you blocking up every ventilation point?

Is it just because you can really feel the dafts and they annoy you?

Or is it because you want to make the house as airtight as possible to keep the heat in? You seem to be concerned over slight air gaps in areas you have already insulated?

Moisture and damp will only be a problem if you completely seal up the house and have no ventilation at all. ventilation is just as important as insulation, without a balance of the two, you get problems....

Here are two other forums where your question has been discussed in length before:

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9851

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9578&page=1#Item_0

 

[dishman]

Also discussed in this link:

http://www.superhomes.org.uk/forum/topic/insulating-timber-suspended-floor/

Hope they help.

 

[WabbitPoo]

I have the same issue upstairs - all the cupboards are really chilly and when the wind blows hard (as it does in Wales!) we get terrible draughts up thru the floor and from within the cupboards.

I was contemplating just sticking down plastic sheet over the floorboards where i can get to them, sealing with sealant around the edges then putting carpets back down again. Is that a bad idea?

 

[myk3]

Thanks for the link but i think they are referring to the ground floor and not the 1st floor. Please see below an image of what I am proposing to the ends of all voids at the external walls on the upstairs floors.

Untitled

• myk3
• 15 Jan 2014
• 1

I appreciate that normally this floor void needs ventilation as condensation should not form as the void will roughly be the same temp as the house and heat up with the central heating. My worry would be that if penetrating damp was to get through to the floor voids at the external walls where I plug the ends with celotex (as pictured) that this moisture will be stuck and thus soak into the wood which will then over time rot…

 

[dishman]

What is your overall aim though? Are you trying to insulate your property or is it just because there are some annoying drafts are annoying you?

If you can feel the drafts under the skirting just silicone/calk up the gap.

If there are large gaps in the floorboards fill them in too. The best option (and the reason why they are used in UK houses) is a nice carpet with good underlay. That will fill the skirting gap and stop drafts coming up between the floorboards.

There is a possibility that if you block up all the gaps between the outer wall and the floor joists that you create an area of stale air and condensation could be more prone to form. If depends how well you seal the gaps, how much air movement there would still be in that gap, and the temperature difference in that gap, and how moist/damp the air that gets into the gap will be. This could be further affected by the fact you have solid walls which will generally be colder than cavity walls.

The chance of damp forming in your house would also be greatly exacerbated if you block up all ventilation in the house, air bricks etc. They are there for a reason, your house has to breathe...It is not healthy for you or the house to have no ventilation.

If you remove all natural ventilation, you have to put in ventilation (such as extractor fans) at other points otherwise your house will be much more prone to damp, especially with solid walls.

You could look to MVHR systems but without substantial insulation upgrades, this would be a waste of an investment for a solid wall property.

 

[myk3]

thanks i agree with you its best not to risk it...

ill just close any gaps i find on the outer walls where external drafts are making it in then caulk the gaps at bottom of skirting.

i have carpet in all rooms already.

thanks