Insulating bare floorboards

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How risky is it to have bare floor boards (sanded, gaps sealed, stained and varnished) in terms of insulation? And what are the options for insulating? This is on the ground floor of a 1930's terraced house.

The gap in the foundations is too small for someone to get in there to insulate from below. One person said he removed the floorboards, laid some sort of stiff insulation, and replaced the boards. Another said to lay insulation on the floorboards, and then another set of new floorboards on top.
 
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The first option really - but any air passage beneath the floorboards mustn't be compromised, obviously. Expect some damage if you go down this route though.
The other options will affect the level of the floor and concern the doors, steps etc.
John :)
 
One person said he removed the floorboards, laid some sort of stiff insulation, and replaced the boards. Another said to lay insulation on the floorboards, and then another set of new floorboards on top.
To expand on this, he laid stuiff insulation on top of the joists, hence raising the level of the boards.
 
If you were going to renew the floor, then it would be a good idea to fix slab insulation tightly between the joists and then lay the floor.
To put insulation on top of the joists and then the floor on top of that sounds crackers to me!
In your situation, close fitting skirtings and then carpets would probably be the best, if that's acceptable.
John :)
 
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Carpet is a no go because we have a dog and my girlfriend has problems with dust, allergies. So the consensus is to remove the board and put insulation between the joists, suspending it somehow?
 
Yes, but I do hope its worth it!
You can either cut the slab insulation so it fits tightly, or even fix strips of timber to the side of the joist (bottom) so it rests on that.
Avoid any gaps at all if you can.
John :)
 
My take on this question is to leave it alone.

Lifting T&G boards by anyone unless they are well experienced, never mind a DIY'er, might result in many ruined boards and splits and cracks in the remainder. DIY'ers occasionally nick cables and pierce pipes.
In a word, you might ruin your excellent 1930's floor for the, to me, so so benefits of underfloor insulation.

Otherwise, as above.
 
If it's a 1930's house, surely the boards are square-edged?

IMO mineral wool quilt is easier to fit well, because you can stuff it tightly beteeen the joists with no need for precise cutting. Most of the cold will come from draughts, especially round the edges, so some kind of floor covering is needed if you aren't going to lift the floor.

Under no circumstances obstruct the airbricks that ventilate the subfloor void.
 
No. I've worked on many Victorian semi's, & pre-1914 terraced housing stock and all the boards were T&G.
T&G became mass produced in the late 19th century.

Stuffing mineral wool quilt causes it to lose much of its insulating value - it should be installed loose.
Plus the OP's girl friend has allergies, and mineral wool is not allergy friendly.
 
Perhaps its regional. My 1905 house had square, so did my 1932 house. Same for friends and neighbours, when I looked.

Maybe that's why I am more concerned about draughts through the floor, which wool blocks effectively. I am not suggesting crushing it paper thin, just pushing it into a gap so it fits tightly even if the space is irregular.

Incidentally, I have for several years been using only mineral wool treated with Ecose, which is a Knauf product though also rebranded by the chains. It is brown with a coating which prevents it shedding dust and fibres and makes it much more pleasant to handle. I find the old yellow glassfibre very irritant.
 
Most of the cold will come from draughts, especially round the edges, so some kind of floor covering is needed if you aren't going to lift the floor.

Round the edges where? You mean near the skirtings? The gaps in the floor boards and around skirtings can be filled with caulk.

The floorboards are not T&G but they are also not original, they must have got replaced when the extension was done.

In terms of alergies, the mineral wool will be under the floor so not sure why that matters?
 
My take on this question is to leave it alone.

Ree, do you think there's not much heat loss thru the floor?

Also, do you know how to remove floorboards without damaging them? Any tips? When I used to work as a plumber 15 years ago I remember that floor boards, once we lifted the carpets, were usually in a right state where previous plumber or electricians had removed them. I can remove floorboards myself reasonably well with small damage using bolsters and crowbars. At my plumbing job we used to use a jigsaw with the base removed holding it at 45 degrees to the floor to cut into the board without going thru the joist below. This was dangerous because the blade is not clearing the wood, so if you move too fast then the blade would bash solid wood and kick you. I've now experimented using a circular saw but with that you have to cut into the next floorboard in order to fully cut the one you want to cut. Is there a better way?
 
The floorboards are not T&G but they are also not original, they must have got replaced when the extension was done.

IME you get quite a cold draught through bare square-edged boards. It also carries dirt and dust, especially round the edges.

Once you have lifted one board, the others are easy. You might like a multicutter.

If you can be bothered, I would take them up, pack between the joists and especially round the edges with Knauf mineral wool, and put the floor back. Staple plastic garden netting to the joists to prevent the quilt falling out. If the boards are modern you can probably match any damaged ones.

Clean out the subfloor void and airbricks, and insulate any pipes, at the same time. If you want to lay any cables, including phone, internet, speakers or TVs, use the opportunity. You can fit a floor safe or concealed storage too if you like.
 
If you ae taking the boards up then consider putting a layer of marine (or moisture resistant plywood) on the joits before refiting the floor boards. Then there are no draughts from between the gaps. Will also prevent any dust or particles from the insulation getting into the room.
 
Thanks for all the advice. Can I get a link to an example multicutter JohnD ?
 

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