Suspended floor board Insulation - Tips?

kiteloopy · 17 Jun 2017 at 12:42

Hi All

My flat is grade 2 listed and I have two large rooms (5mx5m) with exposed pine flooring for my bedroom and dining/living room. It's great living in, but really cold in the winter! Not to mention the noises I hear from basement flat when their getting jiggy!

I popped open one of the floorboards and there is zero insulation in the suspended wooden floorboards. Taking a look online, I need to install some natural fibre based insulation such as sheep’s wool or hemp fibre so that its fitting with a grade2 building.

Has anyone else installed any insulation between floorboards or got any suggestions on how to install it? Taking a look online, people seem to install a net for the fibre to suspend in. Is this necessary? How easy it is to install myself? Id prefer to lift maybe 2-3 floor boards and push it to the end. Is that suitable?

Cheers
J/K

rexehuk · 17 Jun 2017 at 16:48

Don't think you need a net at all. Currently installing rockwool in all internal floors of my house mainly for sound insulation (bought sound blocks) - But you cut it to above size and squeeze it in, and it's going nowhere.

Yes it's easy, definitely a DIY job assuming the boards come up easy. You can calculate the insulation you'd need to add (there are building regs), apparently any "renovation" to insulation has to comply, which is amusing. I'd personally go with the "something is better than nothing" approach and at a guess around 100mm would suffice.

http://www.ccfltd.co.uk/Trade-Support/Calculating_U_Values

Lumeycom · 17 Jun 2017 at 17:23

just be careful you dont put any weight (or compress the insulation too much) on the lathe and plaster as its quite fragile

robj20 · 17 Jun 2017 at 19:40

It will also down rate any wiring going through it. So maybe need to keep that in mind.

a1ex2001 · 18 Jun 2017 at 03:56

Insulating bettween dwellings might need checking with building control I suspect there are some regs to follow.

eviled · 18 Jun 2017 at 09:26

Breathable earth wool, with gaps around electrics and light fittings.

I'm doing my suspended floors that way

kiteloopy · 18 Jun 2017 at 20:58

eviled said:
Breathable earth wool, with gaps around electrics and light fittings.
I'm doing my suspended floors that way

Ive seen on the historice Uk website https://historicengland.org.uk/images-books/publications/eehb-insulation-suspended-timber-floors/ that id need pure natural materials (wool/hemp). Earth wool seems to contain fibreglass which isnt recommended for listed buildings (according to the PDF on that weblink).

https://historicengland.org.uk/images-books/publications/eehb-insulation-suspended-timber-floors/

rexehuk said:
Don't think you need a net at all. Currently installing rockwool in all internal floors of my house mainly for sound insulation (bought sound blocks) - But you cut it to above size and squeeze it in, and it's going nowhere.
Yes it's easy, definitely a DIY job assuming the boards come up easy. You can calculate the insulation you'd need to add (there are building regs), apparently any "renovation" to insulation has to comply, which is amusing. I'd personally go with the "something is better than nothing" approach and at a guess around 100mm would suffice.
http://www.ccfltd.co.uk/Trade-Support/Calculating_U_Values

Well that sounds good! Do I literally fill the complete void? or do I need to leave a few cm/mm to allow for a 'a bit of air flow'? Each joist void is 32cm wide and 21cm high.

robj20 said:
It will also down rate any wiring going through it. So maybe need to keep that in mind.

Thanks for the advice. Any electrical wire and plumbing will be given a wide berth if I can.

a1ex2001 said:
Insulating between dwellings might need checking with building control I suspect there are some regs to follow.

I'll give the council a call to see what they recommend.

rexehuk · 22 Jun 2017 at 23:00

kiteloopy said:
Well that sounds good! Do I literally fill the complete void? or do I need to leave a few cm/mm to allow for a 'a bit of air flow'? Each joist void is 32cm wide and 21cm high.

I'm a complete DIYer. For me I'm using 100mm rockwool, and filling between floor joists which has about a 210mm void. I could go thicker but don't see much point as these are internal floors.

I like the idea of a bit of airflow under there, wouldn't want insulation sandwiched between ceiling and floor as could cause issues I suspect... Additionally I'll be ensuring any cables are not completely covered by the rock wool, resting on it I don't see an issue with (completely fireproof).

Derek W · 23 Jun 2017 at 13:35

a1ex2001 said:
Insulating bettween dwellings might need checking with building control I suspect there are some regs to follow.

To be fair if there's a flat below it should be separated for fire and sound. Obviously not at the time of the conversion but would they insist on any sort of upgrade at all?

rexehuk · 23 Jun 2017 at 14:08

Pringle W said:
To be fair if there's a flat below it should be separated for fire and sound. Obviously not at the time of the conversion but would they insist on any sort of upgrade at all?

Yes. If you're doing works below sub floor technically you're meant to then visit the insulation building regulations and comply. I doubt anyone actually does this when doing DIY... I mean it's additional cost and if you had to comply with every single building condition no one would ever do anything. I doubt even a builder would follow everything to the letter.

If it's a flat below, personally I'd insulate out of want - Blocking out sound and ensuring they don't disturb me (and hey some anti-fire is always nice). I'd be pretty sketchy about disturbing their ceiling though, I would probably play safe and stick a few batons in to ensure the insulation doesn't sink, not like it weighs a lot though.

a1ex2001 · 23 Jun 2017 at 21:11

rexehuk said:
Yes. If you're doing works below sub floor technically you're meant to then visit the insulation building regulations and comply. I doubt anyone actually does this when doing DIY... I mean it's additional cost and if you had to comply with every single building condition no one would ever do anything. I doubt even a builder would follow everything to the letter.

If it's a flat below, personally I'd insulate out of want - Blocking out sound and ensuring they don't disturb me (and hey some anti-fire is always nice). I'd be pretty sketchy about disturbing their ceiling though, I would probably play safe and stick a few batons in to ensure the insulation doesn't sink, not like it weighs a lot though.

It's the fire rather than insulation regs I would worry about only one of those runs the risk of putting you behind bars. i don't know what if any rules apply but I would certainly check with building control!

thezappa · 23 Jun 2017 at 21:27

Could you use blown insulation, specifically cellulose. Its non flammable (just smoulders, I don't have the rating to hand).
About sound insulation; putting insulation in the floor will help but vibration noise through the joists will also contribute. In an ideal world you would take up some of the floor boards and put in a flanking strip.