sub floor

[dapperman]

Hello,

I’ve doing an extension which isn’t very big about 8ft by 6ft. Problem is that i need airbricks as i’m having a sub timber floor. I only have one side that i can put air bricks on and it is tricky. As it a small extension, I was wondering if i could put air vents in the floors maybe 2 or 3 as this will allow air to get underneath. The vents are shown below:

Thank you!

 

[dapperman]

Can someone help me out with this.

Thanks

 

[oldbutnotdead]

Check with your bco- those floor vents will cause massive draughts. One solution is duct in to the side you can't ventilate (110mm waste pipe) so you get a through draught, which is what you need

 

[dapperman]

Hi.

On second thought I see I can get these telescopic air vents which i will most likely put 2 on 1 sides and on another side another 2. Do these vents bridge the cavity, as does the neck touch both skins or does it only touch one and then go onto the other skin with the brick head bit.

Thanks

 

[oldbutnotdead]

Oh so you have 2 sides you can get at? Those telescopic things are designed so the vertical bits are in the cavity and the horizontals in the brickwork. Easy to fit when building, pain as a retrofit- you'll have to cut a block or 2 out

 

[dapperman]

Oh so you have 2 sides you can get at? Those telescopic things are designed so the vertical bits are in the cavity and the horizontals in the brickwork. Easy to fit when building, pain as a retrofit- you'll have to cut a block or 2 out

Yep, two sides but the usually air bricks usually go horizontal, but after i found these i can now go down a couple of courses. Can i also put this on the course of the dpc and lay the dpc on top of these air bricks?

Cheers

 

[electrified]

Oh so you have 2 sides you can get at? Those telescopic things are designed so the vertical bits are in the cavity and the horizontals in the brickwork. Easy to fit when building, pain as a retrofit- you'll have to cut a block or 2 out

hi @oldbutnotdead, could you help me out with a dpm question. i have posted on here but i am still not understanding. i have a timber raised floor, and am getting mixed answers whether or not to put a dpm between the sand blinding and the 50mm of concrete. A person has said that do put a polyethylene membrane down ( not dpm) to stop “weeds”, but i’m sure that a dpm is made of polyethylene.

Your help would be great thanks.

 

[oldbutnotdead]

This is for the subfloor? Yes put dpm down, it helps reduce the water vapour under the floor.
EDIT Yes standard DPM is polythene sheet (polythene being short for polyetheline)

 

[oldbutnotdead]

Yep, two sides but the usually air bricks usually go horizontal, but after i found these i can now go down a couple of courses. Can i also put this on the course of the dpc and lay the dpc on top of these air bricks?

Cheers

Yes, stick some mortar round/on top of the plastic thing so you don't end up with a mouse-size gap

 

[dapperman]

Yes, stick some mortar round/on top of the plastic thing so you don't end up with a mouse-size gap

Cheers mate just what I needed to know

Thanks.

 

[electrified]

This is for the subfloor? Yes put dpm down, it helps reduce the water vapour under the floor.
EDIT Yes standard DPM is polythene sheet (polythene being short for polyetheline)

correct and once i lay my sand blinding then the dpm, does this just butt up with the brickwork, as someone said to connect it to the dpc? then i lay my 50mm concrete. thanks

 

[oldbutnotdead]

correct and once i lay my sand blinding then the dpm, does this just butt up with the brickwork, as someone said to connect it to the dpc? then i lay my 50mm concrete. thanks

You should turn the sides up a bit so the concrete is separated from the brickwork but with suspended timber you don't really want a lined swimming pool under the floor so no don't link to dpc

 

[electrified]

You should turn the sides up a bit so the concrete is separated from the brickwork but with suspended timber you don't really want a lined swimming pool under the floor so no don't link to dpc

thank you, straight to the point, perfect.

 

[electrified]

You should turn the sides up a bit so the concrete is separated from the brickwork but with suspended timber you don't really want a lined swimming pool under the floor so no don't link to dpc

sorry going back to this answer, turning the dpm up so the 50mm concrete slab doesn’t touch the brickwork at all, wouldn’t weeds grow up between the dpm upfield and brickwork as the concrete isn’t covering it all?

 

[oldbutnotdead]

If you puddle the concrete well into the edges and corners there won't be much of a gap.
If you've dug out the topsoil there won't be many weed seeds left.
And don't know about your house but there's not a lot of sunlight in my subfloor (which plants need to grow).
So don't worry about it