Hi there

I did have a quick look but couldn't find the exact answer to my question /scenario.

I'm going to be insulating the suspended timber floor of our Victorian terrace which is the middle room of the house, part of this is an external wall, part runs through to kitchen. The front room has already been insulated with Thermafleece which was lovely stuff to work with. The front room has 3 air vents which provides lots of ventilation. The subfloor was left uncovered when I did the floor in the front room as the sun floor was dry.

In the middle room I'm using foil backed PIR boards mainly because of access issues from above. In the middle room there's one air brick along an external wall which is 1.4m long, so there is cross ventilation front front to back. The room is roughly 3.47m x 4.59m. There was no air brick before I fitted that a few years ago, I was really surprised at this but I assume this is because air could travel through the breathable earth 'slab' which is under the kitchen.

I'm in a quandary as to whether I need to put a Dpm sheet over the earth subfloor? this would have sand blinding underneath it and concrete scattered over it to hold it down?

Why am I considering doing it in this room compared to front room? Different materials is one, with PIR being reflective. Less ventilation is another...

The floor *seems * dry, there are old pieces of wood sat on the floor which haven't deteriorated but the other day I left a transparent dust sheet over part of the floor and within a day or so water did bead up under the sheet.

So to Dpm or not to Dpm, that is the question?

Posted By: tonyWeirdly even though everyone thinks damp emanates from the ground in fact even if it is wet moisture is being transported from the house into the ground! Due to differences in partial vapour pressures

Posted By: meigh985the other day I left a transparent dust sheet over part of the floor and within a day or so water did bead up UNDER the sheet.