Hi all

This won't be a DIY project we'll undertake ourselves, more for general
advice.

We have had an offer accepted on a 3 bed mid-terraced house about 100
years old. As is typical, the house is suspended on wooden joists close
to ground level. It is L shaped with a ground floor bathroom built on as
an extension to the kitchen at the back. This is on a concrete
foundation probably many years ago as the house was never originally
built with a bathroom. In addition, to the right of the kitchen/rear of
the dining room a conservatory/lean-to has been constructed and the
floor has been concreted up to the height of the floor in the house.

We had a full buildings survey carried out which we have read through.
One "serious" defect raised is lack of sub floor ventilation to the rear
as a result of no air brick vents. We suspect they did exist but were
effectively blocked off/removed whenever the bathroom extension was
built and the lean-to floor concreted over. There is one air brick
located underneath the front door which again the surveyor has pointed
out is too small.

The result of this could mean stagnant damp and dry rot to the under
floor timbers. Of course they surveyor could not prove presence of dry
rot under the floor especially as the kitchen floor is tiled and the
hall/living rooms etc, are carpeted.

Our doubts are whether the back part of the house has not had proper
sub-floor ventilation for many years (since the bathroom extension was
build possibly many years ago?) and yet could be perfectly OK to this
day. However it may not.

Various recommendations have been suggested which basically mean more
air bricks to be fitted. Suggestions are to insert them by channelling
into the lean-to floor underneath the door from the dining room again
which leads out to the lean-to. Also one to be inserted into timber
floor where it abuts the solid floor in the doorway from the kitchen to
the bathroom extension. This is suggested with the "disclaimer" it will
cause draughts and must not be covered.

One fairly drastic suggestion is that a channel is laid from the back of
the house underneath the bathroom and kitchen as far as the hall.

Any thoughts would be appreciated.

Thanks.

--
Phil Richards, London, UK

Phil Richards wrote:
Hi all

This won't be a DIY project we'll undertake ourselves, more for general
advice.

We have had an offer accepted on a 3 bed mid-terraced house about 100
years old. As is typical, the house is suspended on wooden joists close
to ground level. It is L shaped with a ground floor bathroom built on as
an extension to the kitchen at the back. This is on a concrete
foundation probably many years ago as the house was never originally
built with a bathroom. In addition, to the right of the kitchen/rear of
the dining room a conservatory/lean-to has been constructed and the
floor has been concreted up to the height of the floor in the house.

We had a full buildings survey carried out which we have read through.
One "serious" defect raised is lack of sub floor ventilation to the rear
as a result of no air brick vents. We suspect they did exist but were
effectively blocked off/removed whenever the bathroom extension was
built and the lean-to floor concreted over. There is one air brick
located underneath the front door which again the surveyor has pointed
out is too small.

The result of this could mean stagnant damp and dry rot to the under
floor timbers. Of course they surveyor could not prove presence of dry
rot under the floor especially as the kitchen floor is tiled and the
hall/living rooms etc, are carpeted.

Our doubts are whether the back part of the house has not had proper
sub-floor ventilation for many years (since the bathroom extension was
build possibly many years ago?) and yet could be perfectly OK to this
day. However it may not.

Various recommendations have been suggested which basically mean more
air bricks to be fitted. Suggestions are to insert them by channelling
into the lean-to floor underneath the door from the dining room again
which leads out to the lean-to. Also one to be inserted into timber
floor where it abuts the solid floor in the doorway from the kitchen to
the bathroom extension. This is suggested with the "disclaimer" it will
cause draughts and must not be covered.

One fairly drastic suggestion is that a channel is laid from the back of
the house underneath the bathroom and kitchen as far as the hall.

Any thoughts would be appreciated.

Thanks.

fill the subfloor in with concrete, DPM, insulation and screed, and put
the floor boards back over it.

Enough ventilation to stop rot is enough to cause bloody draughts.

Did the survey actually find evidence of rot in the floor timbers?
I've seen similar situations as you describe - with blocked or non-
existent provision for underfloor ventilation - and yet the underfloor
space and ground underneath is bone dry.

Probably more important than ventilating the airspace is good drainage
around the building - no adjacent soakaways, or leaking drains, and
the surrounding ground naturally draining away from the building.

Other factors will be gaps between floorboards, room ventilation,
floor-coverings and position of furniture - all contributing to the
underfloor space being ventilated by other routes.

Were there any signs that the floorboards had patched repairs -
particularly along on side next to an outer wall?

If there hasn't been problems so far, and you keep the building dry
and well ventilated - things are likely to continue the same way.

However, once the house is yours, pull up boards in a couple of places
and check what's going on. You may even find the space is ventilated
by a route the surveyor was unable to see.

RubberBiker wrote:
Did the survey actually find evidence of rot in the floor timbers?

No as all the ground floor is carpeted or tiled over.

Probably more important than ventilating the airspace is good drainage
around the building - no adjacent soakaways, or leaking drains, and
the surrounding ground naturally draining away from the building.

Noted. Also no sign of rising damp suggesting the ground below is not
particularly wet?

Other factors will be gaps between floorboards, room ventilation,
floor-coverings and position of furniture - all contributing to the
underfloor space being ventilated by other routes.

The kitchen is fully tiled, the rest of the ground floor reception room
& hall is carpeted. We plan to leave it that way.

Were there any signs that the floorboards had patched repairs -
particularly along on side next to an outer wall?

Not seen as carpeted or tiled over. This is always a disclaimer
surveyors write in as they never lift up floor coverings. I doubt for
one minute a vendor would agree for us to do it.

--
Phil Richards, London, UK
3,600+ railway photos since 1980 at:
http://europeanrail.fotopic.net
http://britishrail.fotopic.net

Phil Richards wrote:
Hi all

This won't be a DIY project we'll undertake ourselves, more for
general advice.

We have had an offer accepted on a 3 bed mid-terraced house about 100
years old. As is typical, the house is suspended on wooden joists
close to ground level. It is L shaped with a ground floor bathroom
built on as an extension to the kitchen at the back. This is on a
concrete foundation probably many years ago as the house was never
originally built with a bathroom. In addition, to the right of the
kitchen/rear of the dining room a conservatory/lean-to has been
constructed and the floor has been concreted up to the height of the
floor in the house.
We had a full buildings survey carried out which we have read through.
One "serious" defect raised is lack of sub floor ventilation to the
rear as a result of no air brick vents. We suspect they did exist but
were effectively blocked off/removed whenever the bathroom extension
was built and the lean-to floor concreted over. There is one air brick
located underneath the front door which again the surveyor has pointed
out is too small.

The result of this could mean stagnant damp and dry rot to the under
floor timbers. Of course they surveyor could not prove presence of dry
rot under the floor especially as the kitchen floor is tiled and the
hall/living rooms etc, are carpeted.

Our doubts are whether the back part of the house has not had proper
sub-floor ventilation for many years (since the bathroom extension was
build possibly many years ago?) and yet could be perfectly OK to this
day. However it may not.

Various recommendations have been suggested which basically mean more
air bricks to be fitted. Suggestions are to insert them by channelling
into the lean-to floor underneath the door from the dining room again
which leads out to the lean-to. Also one to be inserted into timber
floor where it abuts the solid floor in the doorway from the kitchen
to the bathroom extension. This is suggested with the "disclaimer" it
will cause draughts and must not be covered.

One fairly drastic suggestion is that a channel is laid from the back
of the house underneath the bathroom and kitchen as far as the hall.

Any thoughts would be appreciated.

Thanks.

You can put vents in the walls above ground level in your conservatory, but
they will be staggered with the corresponding vents underneath your internal
wooden floors, nevertheless, it will create a cross-flow of ventilation,
which is what you are aiming for.

Obviously you will need more vents at the front, but these should present no
problems, but again, if the outside levels have been raised so that you
can't get them underneath the DPC (internal floor level), then you can use
the method described above

--
Phil L
RSRL Tipster Of The Year 2008

On Mon, 08 Jun 2009 22:43:52 +0100, a certain chimpanzee, Phil
Richards randomly hit a keyboard and
produced:

We have had an offer accepted on a 3 bed mid-terraced house about 100
years old. As is typical, the house is suspended on wooden joists close
to ground level. It is L shaped with a ground floor bathroom built on as
an extension to the kitchen at the back. This is on a concrete
foundation probably many years ago as the house was never originally
built with a bathroom. In addition, to the right of the kitchen/rear of
the dining room a conservatory/lean-to has been constructed and the
floor has been concreted up to the height of the floor in the house.

We had a full buildings survey carried out which we have read through.
One "serious" defect raised is lack of sub floor ventilation to the rear
as a result of no air brick vents. We suspect they did exist but were
effectively blocked off/removed whenever the bathroom extension was
built and the lean-to floor concreted over. There is one air brick
located underneath the front door which again the surveyor has pointed
out is too small.

The result of this could mean stagnant damp and dry rot to the under
floor timbers. Of course they surveyor could not prove presence of dry
rot under the floor especially as the kitchen floor is tiled and the
hall/living rooms etc, are carpeted.

Our doubts are whether the back part of the house has not had proper
sub-floor ventilation for many years (since the bathroom extension was
build possibly many years ago?) and yet could be perfectly OK to this
day. However it may not.

Various recommendations have been suggested which basically mean more
air bricks to be fitted. Suggestions are to insert them by channelling
into the lean-to floor underneath the door from the dining room again
which leads out to the lean-to. Also one to be inserted into timber
floor where it abuts the solid floor in the doorway from the kitchen to
the bathroom extension. This is suggested with the "disclaimer" it will
cause draughts and must not be covered.

Whoever built the extensions should have run 4" pipes under the slabs
wherever there had been an air brick to vents coming up through the
cavity to air bricks on the external elevation below DPC. I say,
"should"; it doesn't always happen, and happens even less with
conservatories (which are exempt from Building Control inspections).

The suggestion, which if I read it right, to ventilate the sub-floor
void INTO the building sounds bizarre, and would almost certainly
cause more problems by providing an easy path for warm, moist air from
inside the building into the cold sub-floor void. As suggested
elsewhere, if there is no cross ventilation, it may be better to
replace the joisted floor with a concrete slab.

Give the floors a good stamping, especially close to the walls to see
if there is any movement in the joists. If there is rot, the joist
ends and the boards may feel a bit mushy.
--
Hugo Nebula
"If no one on the Internet wants a piece of this,
just how far from the pack have you strayed?"