Breakthrough batteries

[Catweazle]

Is it possible to blow perlite or an equivalent under floorboards on top of dirt ? I have an old house, I've done the loft and external wall insulation, windows are double glazed, so the floor is the weak link. I run a de-humidifier all the time, as previous owners had neglected the roof and a lot of water is in the ( 3 foot thick ) walls.

I dug out the gravel from the "ditch" surrounding the house before the external insulation went on, so the insulation goes quite deep, do you have any advice on re-filling it ? There are no foundations as such, it appears to be build on bedrock or at least on some very large slates. The gravel had also been neglected, it was completely clogged with many, many years worth of leaf litter,

Any advice appreciated.

[biffvernon]

Thanks for that, Biff. I wonder what influences are in play to make the use of mud and stud prevalent over wattle and daub? Perhaps it's greater wind speed in Linconshire demanding a thicker better insulated and wind proof construction than wattle and daub provides.

It's probably mostly a case of that was the way dad and granddad did it so that's the way I'll do it. Good quality oak may have been a bit scarcer in Lincolnshire than some other parts so covering up the wonky timber with mud might have been handy.

In the cutaway of the M&S house they show the posts going down to only a couple of courses above ground level. I would have thought that starting off a plate on top of the brick would have given a more long lived structure by keeping the timber away from rising moisture, in the same way that cob and the M&S is given protection.

Which may explain why very old mud and stud buildings are getting pretty rare! There's a fair bit of variation and clearly the higher you keep the timbers off the marsh the better. But bricks and stone were expensive.

[kenneal - lagger]

The underfloor void should always be ventilated, Catweazle, to remove moisture and prevent dampness from building up. The best way to insulate a suspended floor is to take the floor up and fix insulation between the joists, at least, and, preferably if possible, under them as well while maintaining the air movement. Having said that, I've just built an insulated shed on a foundation of tyres laid on the ground infilled with Lecafil, an insulation product made from sintered clay balls so your Perlite wouldn't be a lot different.

The Perlite is a much smaller particle size though so might reduce any vapour movement more which might increase the likelihood of damp problems but would give a higher insulation value until the damp set in. Just thinking out loud here really. You would want to install a vapour barrier/damp proof membrane between the underside of the floor structure and the insulation to keep moisture out of the floor. It would have the effect of concentrating any moisture under the floor into the wall area so might make the walls damper. If some form of drain could be arranged for the underfllor area if it was very wet that would help.

Your gravel drain outside should always be below floor level so that any water splashing up from it gets a chance to dry out before it goes through the wall into the floor or plaster. Did the gravel drains flow out to free air anywhere or did the water just accumulate? If there was a flow through or a flow through could be arranged it would help to speed the flow, and hence reduce any silting up, if a perforated or slotted pipe, minimum 75 dia, was set at the bottom of the trench to make a proper French drain before the gravel was returned.

Weedproof mat laid on top of the drain and covered with a thin layer of gravel would make it easier to keep the main part of the drain clean. Hope that helps.

[Catweazle]

Thanks Ken, food for thought.