insulating draughty cavity under ground floor boards?



Approved Document L1B, 5.7 b. i. defines the replacement of an existing layer as "stripping down the element to expose the basic structural components (brick/blockwork, timber/metal frame, joists, rafters, etc)..."
So I guess if you take up the floorboards, strictly speaking it's notifiable. I wouldn't bother, and I bet nobody has.
Cheers Richard
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
In article

Agreed, thanks for pointing out the exact wording that makes it far clearer.
When I did mine I worked below from an existing hatch but in one area had to lift a few board to do the poke fill method which (even if I was bothered) shouldn't have required a notice.
Although it's been suggested here, I wouldn't lift all the boards, vapour barrier considerations or not.
It's wise to take care if there is a compliance bod in the vicinity.
--
fred
FIVE TV's superbright logo - not the DOG's, it's bollocks
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

However, I have not heard a word suggesting that this will happen or not happen
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 24 Dec,

Hasn't it to be more than 25% of the element to be notifiable? You did some last year and some the year before etc. didn't you?
--
B Thumbs
Change lycos to yahoo to reply
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Yes, but it's 25% of that element, not of all the elements of that type in the house. ie if you expose more than a quarter of the floor in one room. It's all academic anyway, who the hell is going to notify Building Control if they're insulating a floor, and what are Building Control going to do anyway, tell you to take it out again? Really not worth worrying about.
Cheers Richard
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
geraldthehamster wrote:

Basically talked this over with a mate, who is doing up house to sell when things improve.. No BCO, no ticket. No ticket no resale value increase.
No insulation!

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 25/12/10 02:56, The Natural Philosopher wrote:

I never understand this - I don't fix houses for resale value, I fix it so I like it...
In your mate's case, if there really was a resale value potential increase, and he felt the BNA sign off was actually worth something, why not just get a BNA - for that value of work it would only be a couple of hundred?
--
Tim Watts

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Tim Watts wrote:

He hasn't got even a couple of hundred.
And the estate agent was dubious as to whether even so, it would increase the house value.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 25/12/10 12:12, The Natural Philosopher wrote:

I guess that brings it back to - do it if *you* want to and stop thinking about estate agents :)
--
Tim Watts

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Tim Watts wrote:

In his case it was simple cost benefit. He's been ill for years and cant do full time work. Wife works in estate agents, retirement looms, kids gone, so everything is 'what is the least amount of money I can spend using my spare time to maximise the nest egg'
Cost benefit of underfloor insulation was negative, on best advice.
In terms of resale value.
We all agree in terms of heating bills and comfort its a winner all the way.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
fred wrote:

That depends on whether you call adding insulation a 'material change' or not.
Since insulation is fully covered in the regulations, it would seem likely that it is so considered.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

There has been an awful lot of misinformation and with some small amount of good corrections. It is best to insulate. Do so such that the timber remains warm and thus not at risk of condensation. If it is warm it does not need ventilation of the sub-floor airvents but they should be left in regardless for keeping moisture levels low in the abutting masonry and oversite. This is what I would recommend on our pro bono terms. lift all fbs labelling so they go back in same places use a proper floorboard lifter if you can hire or or borrow one if not use long long levers with flat iron heads glue any that split
When lifting use a hammer and fulcrum to knock them out with the nails rather than trying to lift the nailed boards up direct (like knocking the other end of a see saw) Put in polythene sheeting on the oversite and put on some sand to keep it down in place (reduces water vapour entry into void)
put in PU 4" foam with a careful cut filling any gaps with foam gun get under and put one or two inches of foil-backed PU under the lot cross ways using large plastic washers and long enough nails (or battens) and leave just a small hole for you to get up back inside and then put the last bit in and hold it up with string or whatever from the inside fill the last gap between FBs put on a vapour check such as thin poly Fbs back down either in right places or cramped together with a replacement to take up the slack
Job done Wall plates not at risk if on a DPC joists all warm - you warm as toast
can have boards or carpet as you wish U Value probably (guess) 0.25 bobs yer uncle
no decay risk from oversite
chris
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Blimey, talk about putting the OP off. Yes, if you wanted to rip up your entire floor and get underneath it, and had an unlimited budget for PU boards, you could do all that. Theoretically you'd eliminate cold bridging across the joists, but really I don't think you'd feel the benefit under floor of 6 inches of PU board (which is closer to the standard for rafters, not floors), as opposed to 2 inches of board or a roll of space blanket between the joists.
Cheers Richard
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.