Suspended timber floors - old house

beggars_bush

Anyone recommend a way to insulate the suspended timber floors in a few rooms in an old house?

Timbers joists are in great condition, there are exterior vents
The red deal timber floorboards are immaculate having been covered by carpet for 50 years.

athlone573

beggars_bush wrote: »

Anyone recommend a way to insulate the suspended timber floors in a few rooms in an old house?

Timbers joists are in great condition, there are exterior vents
The red deal timber floorboards are immaculate having been covered by carpet for 50 years.

I think you can put aerobord between the joists but it may cause problems with air circulation and damp, but ask an expert. I'm not sure it's with the effort,presumably you'll be sorting the walls and attic as first priority.

Not what you asked but red deal can look great sanded and varnished, although technically a softwood you'll get a good few years out of it.

Alkers

https://www.ecologicalbuildingsystems.com/post/best-practice-approach-insulating-suspended-timber-floors

beggars_bush

Alkers wrote: »

https://www.ecologicalbuildingsystems.com/post/best-practice-approach-insulating-suspended-timber-floors

Thanks
Had seen that online

beggars_bush

athlone573 wrote: »

I think you can put aerobord between the joists but it may cause problems with air circulation and damp, but ask an expert. I'm not sure it's with the effort,presumably you'll be sorting the walls and attic as first priority.

Not what you asked but red deal can look great sanded and varnished, although technically a softwood you'll get a good few years out of it.

Thanks
Yes, might sand up the red deal. We'll see.

The attic is well insulated funnily enough.
The exterior walls we're still debating what to do - dry lining will presumably involve doing it all the way down inside the crawl space under timber floors too. The house is quite high up off foundations and there is a high plint around the exterior

bassy

this is what i done and it really improved my room,but i had to lift all the floor boards as the were rotten.so when i was at it i insulated between the joists etc

https://www.boards.ie/vbulletin/showthread.php?t=2058081665

TheBoyConor

Rather than lifting, insulating and reboarding, you might be better to just put in a concrete floor

beggars_bush

TheBoyConor wrote: »

Rather than lifting, insulating and reboarding, you might be better to just put in a concrete floor

5 rooms to be done

Calahonda52

TheBoyConor wrote: »

Rather than lifting, insulating and reboarding, you might be better to just put in a concrete floor

with 6 months drying out?

BoardsMember

beggars_bush wrote: »

The exterior walls we're still debating what to do - dry lining will presumably involve doing it all the way down inside the crawl space under timber floors too. The house is quite high up off foundations and there is a high plint around the exterior

Why would you need to dry line below the floor level? Surely if airtightness and insulation is achieved at floor level, you just need to ensure the dry lining is airtight between wall and floor?

beggars_bush

BoardsMember wrote: »

Why would you need to dry line below the floor level? Surely if airtightness and insulation is achieved at floor level, you just need to ensure the dry lining is airtight between wall and floor?

Yeah, you are probably right
I jut saw it being done on some online blog about renovating an old building with suspended timber floors

BryanF

athlone573 wrote: »

I think you can put aerobord between the joists but it may cause problems with air circulation and damp, but ask an expert. I'm not sure it's with the effort,presumably you'll be sorting the walls and attic as first priority.

it’s worth the effort, I’ve done it. Breathable membrane between folded down between joists, mineral wool insulation, air-tightness tape and sealed. If you don’t block the sub-floor vents, there should be no issue with dampness, and using breathable materials or avoiding polystyrene etc is best.

BoardsMember wrote: »

Why would you need to dry line below the floor level? Surely if airtightness and insulation is achieved at floor level, you just need to ensure the dry lining is airtight between wall and floor?

Drylining below floor level provides an insulation over lap with the floor insulation as dry lining is never continuos. I foamed rigid insulation around the perimeter of the rising walls in the sub- floor, ensuring I didn’t block the vents.

beggars_bush

BryanF wrote: »

it’s worth the effort, I’ve done it. Breathable membrane between folded down between joists, mineral wool insulation, air-tightness tape and sealed. If you don’t block the sub-floor vents, there should be no issue with dampness, and using breathable materials or avoiding polystyrene etc is best.


Drylining below floor level provides an insulation over lap with the floor insulation as dry lining is never continuos. I foamed rigid insulation around the perimeter of the rising walls in the sub- floor, ensuring I didn’t block the vents.

Thanks for the reply

So the breathable membrane goes across the room, up across down each joist? Then mineral wool between each joist? Will the membrane hold up the wool insulation?

BryanF

beggars_bush wrote: »

Thanks for the reply

So the breathable membrane goes across the room, up across down each joist? Then mineral wool between each joist? Will the membrane hold up the wool insulation?

Ye role it out, and fold it down between the joists and staple it. Simples

bassy

beggars_bush wrote: »

Thanks for the reply

So the breathable membrane goes across the room, up across down each joist? Then mineral wool between each joist? Will the membrane hold up the wool insulation?

you can use builders twyne to hold up the insulation as thats what i did,tack it near bottom of joist and do zig zags etc so it will hold the insulation.

bassy

i also put a breathable membrane over the insulation and taped everything,then i put down the new red dale floorboards.

athlone573

Great info there.

I've been involved in two renovations where this might have been possible

On one (50s mass concrete walls about half a metre thick) we just drylined and left the floor alone. This was pre the days of BER so insulating the floor wasn't really considered.

The other one, gutted the place completely put in UFH and a new concrete floor. Obviously a much bigger and more time consuming job.

beggars_bush

athlone573 wrote: »

Great info there.

I've been involved in two renovations where this might have been possible

On one (50s mass concrete walls about half a metre thick) we just drylined and left the floor alone. This was pre the days of BER so insulating the floor wasn't really considered.

The other one, gutted the place completely put in UFH and a new concrete floor. Obviously a much bigger and more time consuming job.

This is a 1960s concrete built land commission house. The house itself is in remarkably good condition.

bassy

beggars_bush wrote: »

This is a 1960s concrete built land commission house. The house itself is in remarkably good condition.

my house is older,and built with precast concrete.but ye very similar to yours.

BryanF

bassy wrote: »

i also put a breathable membrane over the insulation and taped everything,then i put down the new red dale floorboards.

It should be air-tightness membrane above (warm side of) insulation.

Alkers

It's the kind of thing that if you don't do it now you'll never be willing to go back and address it properly