The Holy Grail

Sigh. Having sanded and varnished most of my downstairs floors (suspended over a space too small to access), fitted new skirtings, a hearth and a fireplace (which seemed like quite enough work at the time), I'm now wishing that I'd really bitten the bullet, taken up the floorboards and insulated underneath. Even if I'd demolished most of the tongues in the process, I could have ripped them into straight- edged boards.
I have one room to go, and might go the whole hog there (ironically it's a spare room). But for the rest of the ground floor, the idea of pulling off all the skirtings (how else to remove the T&G boards whose ends go under them, and are fixed with brads an inch from the wall?), and doing the floors again, is heartbreaking, though I might just bite the bullet when I've completed all the other jobs. Or I'll content myself with lots of rugs.
Which leaves the Holy Grail, discussed on here before - how to insulate under a suspended timber floor, with no access from underneath, without removing the floor.
Cheers Richard
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On Oct 4, 10:03 am, geraldthehamster wrote:

Could you cut an access through an external wall?
Or squirty foam.
Owain
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Even if I did cut such an access, there's not enough room for anyone other than an unskilled very small child, and the dwarf walls that support the joists at intervals would necessitate many such holes.
Helium-based squirty foam,that would rise and stick to the underside of the floorboards?
;-)
Oh come on, there must be a way we haven't thought of.
Cheers Richard
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*LOTS* of squirty foam to entirely fill the underfloor void?
Ventilation for your joists? Why would you want ventilation?
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On Mon, 04 Oct 2010 03:51:37 -0700, geraldthehamster wrote:

How much space are we talking about? It's surprising how small a space a human can fit into. Insulating probably doesn't need a lot of clearance, either - no messing with power tools, no need to swing a hammer etc.
cheers
Jules
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On 5 Oct,

Flat panel insulation needs a big hole in the floor to fit if there is no depth, particularly if thick. Flexible insulation is generally an irritant, I don't like getting too close.
I'm toying with pulling through spaceblanket (mineral wool (or is it recycled bottles) wrapped in a plastic film, much less irritating than bare stuff.--
--
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On Wed, 06 Oct 2010 00:21:10 +0100, me9 wrote:

If only you can get in there, you could probably attach some form of fine netting to the underside of the joists and then use blown-in insulation to fill the gaps between the joists.
cheers
Jules
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PROGRESS! There's a solution here, it just needs a bit of fine tuning.
To lay the access thing to bed - I haven't measured the depth of my void (so to speak), but it's no more than 18 inches. Joists are 4x2 at 16 in. centres. Every couple of feet or so is a block dwarf wall which supports the joists, and therefore runs parallel to the boards. You'd have to do so much taking up to get in there, that you might as well take up the whole floor. There is negligible height to work in, and I don't do confined spaces.
Now then - yes, you could pull through spaceblanket, and you'd only need to take up maybe four boards across the room. I like this. However - without taking up numerous boards, how are you going to eliminate sagging, and ensure that it's tight up between the joists?
In my own case, I would also need to feed each run of space blanket through the four-inch gaps where the joists sit on the dwarf walls. This might be doable with stick and bits of wire, but again, needs a bit of finesse.
I can't help thinking that a very small child is part of the solution. I never thought to fabricate any.
Cheers Richard
Cheers Richard
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On Wed, 06 Oct 2010 01:54:46 -0700, geraldthehamster wrote:

If that's 18 inches below the joists, you have no problem. If it's 18 inches including joist depth then it's tight, but probably still do-able. People often under-estimate how small a space they can squeeze into - but I note your point about not liking small spaces :-)
We did a partial house rewire the other week and that was around 9" of void below the joists - but the horizontal space was larger (around 4' between supporting structure). The major pain with that one was the discarded lumps of jagged concrete from some previous structure which were littered around on the ground. Oh, and getting in's a lot easier than getting back out :-)
re. spaceblankets, maybe you need a couple of metal straps holding the blanket tight against the joists? Couple of nails/screws on the side faces of the end joists would do it I'd think - if it's a big room then it might still sag an inch or two in the middle, but I wouldn't expect that to be a problem as the insulation layer would still be tight against the joists at the ends, so heat would still be retained above the blanket layer.

Is the ground below reasonably flat? If so, small RC car to pull a rope or two through, then tie the rope to the blanket to pull that through?
cheers
Jules
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wrote:

Thanks Jules. I was thinking along the lines of a couple of straps running longitudinally each side of the batt of encapsulated space blanket, which could be pulled tight and fixed at each end. If the space blanket were quite thick, and slightly wider than the gap between joists, that might pull it in nicely. I'd maybe aim to remove a board every 3 feet or so, and do it in 3 foot chunks.
I'll measure the depth of the void tonight, just for interest. You won't catch me trying to get in and out of it; besides which I'd need to take up more adjacent boards to get in, than I would separate boards to try the thing with the batts. And you're right about the getting out; I'm not as limber as once I was, though I have lost a fair amount of weight lately.
Cheers Richard
Otherwise, I like idea of the the radio-controlled car ;-)
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On 6 Oct,

I had thought of using tile lath to lay over te dwarf walls to support the spaceblanket

I have used that method in the past.

Mine are now much larger than me.
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We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember geraldthehamster
Easy - peasy.
Flood the underfloor space with wotter and on it float a carpet of sticky foam pellets that will stick to the underside of the joists and floorboards. Drain away the moisture, and there y'go.
It's so good I might just patent it - or I might not bother.
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On Thu, 07 Oct 2010 01:12:58 +0100, Grimly Curmudgeon wrote:

:-) Oddly enough, I almost suggested the same approach, but with expanding foam - but then I got to wondering if that stuff actually floats in water before it's done its expanding and set, and I didn't have any around to test with. Didn't want to give poor advice, so kept quiet.
;-)
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Rats; mice; and wasps seem to be pretty good at filling up under floors with insulation.
Otherwise: foam through the knotholes. The cavity wall insulation people very quickly filled up the walls in my old house. Sure they could quote for floors if you asked.
S
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geraldthehamster wrote:

Filling the entire void is not an option, unless you want your joists to rot away within a few short years.
You can't get access under the floor and you don't want to take the entire floor up? - then it cannot be insulated, end of story.
You could insulate above the existing floor, with 75mm celotex or similar, then put a floating floor above that, but then you'd lose about 90mm of room height (and your internal doors would be 90mm shorter too) plus you'd have to put new skirtings all the way around
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These have been my conclusions, every time I've thought about it :-(
I can only see two ways to make the floor warmer, short of a detested fitted carpet, with its propensity to collect dust, and stains from coffee, wine and mouse blood. Or ripping the lot out and replacing with concrete, which would be stupid and unnecessary ;-)
One is to remove my skirtings, prise up the floorboards, insulate, tidy up the boards on a table saw, refit, fit new skirtings and decorate. In three rooms and a hallway.
The other is to continue to collect relatively inexpensive Persian rugs, and attach Tri-Iso insulation to the backs of them. That way much of the heat loss would be eliminated.
Hence my reference to the Holy Grail - don't bring me common sense, bring me solutions ;-)
Cheers Richard
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Surely only one or two long boards removed would provide access to blow insulation under? Even if you wanted to remove ALL the boards, sawing through the tongue on one with <insert favourite sawing device here> would release them all (once skirtings off).
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Do wonder about insulating under floor voids, roof voids have air and draughts deliberately introduced to stop rot, concerned that creating static air under floor timbers might introduce a rot encouraging enviroment?
Cheers Adam
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Adam Aglionby wrote:

That's why you should use the same system as for rooves. Celotex and leave the air circulation alone.

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Absolutely - it's important not to interfere with the ventilation, which is why you can't simply fill the void through a hole.
cheers Richard
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