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

In article ,
Gavin Willingham writes:
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?

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.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Gavin Willingham wrote:
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?


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.

Cheers
--Gavin

On Sep 9, 11:50*am, Gavin Willingham wrote:
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

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


NT