Vapour barrier disaster.

[AronSearle]

Timber frames do have purpends to provide drainage and ventilation, and he practically speaking has a timber frame wall with sandstone cladding.

So the question, what to do about it? I am thinking that a vent on the external wall into this area would help clear out this moisture and keep it down. Does anybody disagree with this? At this moment I really want to sort this out and not want to revisit this problem later on.

Why is the sandstone wet?

Could it be from the condensation building up behind the VCL and then leaking through, seems unlikely to me, I assume it's wet from other existing issues.

I'd say yes to some vents, but I do not know anything about sandstone, just timber frame.

It may be if you put a breather membrane where the VCL was that will stop the humidity from the cavity (generated by the sandstone) getting to the timber.

 

[blokecalledkev]

Why is the sandstone wet?

Could it be from the condensation building up behind the VCL and then leaking through, seems unlikely to me, I assume it's wet from other existing issues.

Thank you and we think your assumption is correct. Despite our believes that the moisture was a build up from the warm moisture filled air in the kitchen meeting cold air within the void space we now think we have found the root cause of it all.

Directly outside, where all the water is concentrated is a down pipe. It is old metal pipe which disappears into not the best looking drain. We are getting somebody to come out and check it out later this week. But I feel it is no coincidence that this corner, especially, is soaking internally.

It looks very much to me that water from outside is either soaking into the sandstone or seeping in under the house in this area.

I am guessing a new down pipe and drain is in order and I am also guessing that if this is the problem it will take time for the moisture/damp to clear up. When the guy is looking at the pipe I will ask about putting a vent into the external wall.

Sometimes it is the obvious things that can be over looked and although I have no doubt that pinning polythene to the inside of the sandstone wall did not help we are now reasonably sure were the problem lies, old rusty metal down pipes and poor drains. Just what we need before Xmas!!

Kevin.

 

[freddiemercurystwin]

Timber frames do have purpends to provide drainage and ventilation

No they have them for drainage not ventilation.

 

[denso13]

Not what I was led to believe http://www.drillvent.com/tecdata/tecdata_01.pdf or http://www.vents.co.uk/pdf/article2.pdf

 

[freddiemercurystwin]

Maybe

 

[AronSearle]

Freddymercurystwin

There is a bit of an argument as to purpends at the bottom providing ventilation or just drainage, as having them at the bottom does not provide through ventilation (chimney affect), but it's more an argument as to what ventilation is, as it stands purpends are considered to provide ventilation to the cavity.

TRADA's timber frame manual consideres a brick clad cavity to be vented

NHBC also state

Question?

With timber frame construction, does each wall section need to be ventilated at the top and the bottom?

Cavity ventilation is required to control the moisture content of the timber structure.


Answer
Cavities should be ventilated as described in NHBC Standards clause 6.2 – D4(c):

“The cavity should be vented to allow some limited, but not necessarily through, movemnet of air.
Where wall areas are divided by horizontal cavity barriers ventilation openings should be provided to each
section.’’

The ventilation openings should be equivalent to open brick perpends every 1.2m.

The openings may be located either at the top or bottom of each section.

 

[freddiemercurystwin]

Yea OK I'll concede that for traditional timber frame venting is no bad thing. However in this instance, an existing building, further investigation is required in order to ascertain whether the moisture is residue left over from the VP debacle or is seeping through from the outside. In which case ventilation is not the remedial action required.