Insulating under the floor of a 100 year old terrace house

[stuartiannaylor]

Hi, I have been scratching my head really.

We have gone bare floor boards with a danish oil finish. Lovely and low maintenance. The red wine never went with the carpet.

The terrace is built onto soil the walls have a tier of bricks that act as a psuedo foundation.

I want to provide insulation under the floor boards but I am fretting about keeping air movement and stopping the insulation from drawing or retaining moisture.

Anyone any ideas? Or have done this before and have a solution. I was thinking of "tanking" the insulation in visqueen but still worried about airflow.

Many thanks

stuart

[biff]

there are a couple of spray on type insulations that would do the job and be a lot less hassle than fitting kingspan between the joists, but the spray on would certainly block all the gaps in the boards as well as keeping everything snug and as long as the airbricks are kept clear you should not have a problem, well worth looking into,
                                                             biff

[clockmanFR]

Scouts, that is what i used to use.
Wait for bob a job week, offer them serious wads, a fiver each, and down they would go.
Or am i showing my age.

[stuartiannaylor]

Thanks biff,

There is only a couple of feet below the floor boards to bare earth. So getting it sprayed would be awkward.
My main worry is damp as previously we had laminate other the floorboards. This has seemed to cause the boards to sweat near the outside wall.
Woodworm had got into the old victorian pitch pine and I am presuming they had more moisture in them.
Strangely in the small hallway where there was no laminate the floor boards where pristine.
This has just got me in a bit of a panic about trapping moisture and airflow as there are no air bricks on the inner skin.

Clockman if you are paying scouts a fiver to go down, maybe you should keep that to yourself!

[M]

Stuart, I read Clockman's post several times, but just couldn't bring myself to post a reply. Normally I'm happy to take on a ferret with a bad leg, but even I couldn't go that low! 

Martyn.

[biff]

 yeah  yeahhhh,
                   imagine pushing a poor little scout under the floorboards and getting him to breath in all that old grimey dust,,awwwww,,,
     i mean it would be ok if you knew of one who was going round nicking radios and cd players out of cars or doing a little breaking an enterings before bedtime,,,yeahhh yeahhh,,maybe not,,,, wait,,there are loads of old skinny grannies who would do it for a daniel o,donnell cd, i mean,,i mean crawl under the floorboards,,
                                           biff

[M]

yeah  yeahhhh,
                   imagine pushing a poor little scout under the floorboards and getting him to breath in all that old grimey dust,,awwwww,,,
     i mean it would be ok if you knew of one who was going round nicking radios and cd players out of cars or doing a little breaking an enterings before bedtime,,,yeahhh yeahhh,,maybe not,,,, wait,,there are loads of old skinny grannies who would do it for a daniel o,donnell cd, i mean,,i mean crawl under the floorboards,,
                                           biff

Do I take it you have a bit of an obsession with Daniel O'Donnell Biff!

It's funny how different places have there own expressions, I've never heard of 'crawling under the floorboards' before, is that just local to Ireland? Does it just apply to grannies?

It was 13 years ago that I put fluffy loft insulation under our living room floorboards. had to jam a strip between the joist, whilst lying on my back less than feet from the area, then used string and a staple gun to zig zag and lock in place. Worst job I have ever done. Ever done. Still angry to this day, as 3 weeks later went to get more insulation for the loft and discovered the muslin wrapped stuff. AAAAAHHHHHhhhhhh.

Martyn.

[stuartiannaylor]

Hey guys on a more serious note lol.

What do you are your thoughts to trapping moisture, just go with it or provide a vapour barrier?

Stuart

ps dib dib

[M]

Stuart, I've had similar concerns ever since I 'did' the living room. My theory is, my living room is the same as the loft floor in reverse. So, loft has air above insulation and exposed joist edges, the other side is covered with lathe and plaster. Flip that over for living room, so bottom of joists is exposed to air movement under floor, gap between joists filled in with 100mm loft insulation, but floorboards protected by underlay and carpet. I made sure that the insulation I put under the floor didn't obstruct any vents, or air bricks between rooms or outside.

I have no idea if this is ok, would love thoughts and opinions as I don't want to cause any damp, or rot problems.

The floor was dust dry before I did it, and still the same when a new radiator was plumbed in last winter.

I did consider doing the same in the front room, but the drop is 2 bricks less, and I simply can't make the bend to get under! Will be redecorating next year, so have considered similar idea of fitting Kingspan, by taking up all floorboards then just screwing in a few noggins and dropping sheets down, rather than up?

Martyn.

[EccentricAnomaly]

If the laminate caused condensation then I'd guess it did so by acting as a vapour barrier. That would presumably mean that you've got vapour coming up from the ground/"foundations" which needs to escape into the house (rather than the more traditional flow from the low relative humidity but high absolute humidity inside of the house to the outside). If that makes sense then adding any form of vapour barrier seems like a really bad idea - you'd want to keep as much vapour transparency as possible (or add some air bricks).

Are you planning to lift the floorboards?

[stuartiannaylor]

Cheers Eccentric,

Thought as much as the turn of the 20th century mill terrace is a strange construction in modern terms.
There is an air brick on the outside wall which vents a cavity to the roof. The inner skin doesn't so there is damp from the soil flow.
So if I get an air brick on the inner skin below the floorboards I am presuming this will improve maters.
A neighbour of mine said he had major problems with damp. The cavity is to small to qualify for cavity insulation and the bottom of it is full of over a hundred years of mortar and soot which has turned into this very fine soil. He said he removed individual bricks and raked a huge ammount out and solved a major problem. I presume it was just drawing moisture from below.

We did have laminate and that crappy white thin foam insulation under and this did cause all the perimeter floorboards to be replaced. I am sort of stuck in a catch 22 situation where going to bare boards would be nice but obviously not insulated.
So can someone kindly comment on this.
I am going to add a air brick to the inner skin, place rockwool suspended on netting between the joist and hope the air flow up the cavity will keep the moisture to a minimal level?

Many thanks

stuart 

[biff]

awwwww sure its old hat here M,
                      some nights the missus says to me,honeyeeee your getting cold,,pull the floorboards up round your shoulders,,, i might have a bit of a thing for daniel,s mam julia because she makes a great cuppa,,and do you know,,she knitted 2 pairs of socks for the pope,,?? she did..and sent them off to his lordship in the vatican,,a few weeks later she got a very important letter..it was himself,,the guy with the big hat,,thanking julia for the socks and sending a wee pressie of his own.and blessing by the score.but daniel was heard to say,,"awwwwwww fxxk it mam,,yer not going over to italy to see that old codger,sure who will make the taeee".?
                                                                                   biff

[biff]

on a more serious note stuart,
                             if you are going to go to the bother of lifting the boards,then use kingspan on 2 x 1 runners,leave a little gap of 25mm between the boards and the k/s. while you have the boards up you can install a low voltage copper dpc.it can be done very quickly and this will keep the damp from rising up the wall,the only other alternative is to inject each half brick,,(every 100mm) right round under the joists with a soverign silicate chemical,it take time for the injection process but if it is done right it can work well.if the house is 100yrs old then there would be no dpc,hence the rising damp at present.
                                                         biff