Efflorescence beneath DPC under suspended floor

Hi

I've recently bought a house in Cumbria, and have been doing some renovations. I have removed the carpet from one room and want to sand down the floor boards and have a wood floor. I was worried about it being cold, so I decided to insulate under the floor. So far so good. I lifted a few boards to have a look and fit some heating pipes for a new radiator and everything looked fine and dry underneath.

In the last week or so there's been quite a lot of rain (remind me again why I moved to the North..?) and part of the ground beneath the floor has got a bit damp - mostly it seems where rain has come in through the air bricks, but in other patches near the walls too. Practically overnight, quite a few patches of efflorescence have sprung up on (the inside of) the external walls. These patches are all beneath the floor and below the damp-proof course, and I only noticed because the floor was up.

There's nothing obvious outside the walls causing water to stay against the walls, the outside being rendered and painted and a concrete-slab path being immediately outside.

Is this something to worry about, or does the fact it's beneath the DPC mean it's not a problem?

Cheers

--Gavin

Reply to
Gavin Willingham
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I would not have thought that was a problem. In some homes, water will puddle under the floor during periods of excess rain.

However, I would make sure you have plenty of ventilation under the floor, particularly when it will be losing heat gain from the house. The ventilation needs to be able to keep the humidity down even when water has puddled under the floor. Also, without the heat from the house, I suppose the wet bricks down there could suffer frost damage eventually.

Modern plastic airbricks have a water-stop at the rear to prevent any splashes running back into the house. They also have a much larger effective ventilation area than the pottery type.

Reply to
Andrew Gabriel

The latter

Essentially the bricks are sucking up soil borne water and possibly salts, and its just ending up where you found it.

But do ensure the underfloor ventilation is good post insulation.

Reply to
The Natural Philosopher

Efflorescence where you say is what one would expect. Not an issue

NT

Reply to
NT

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