Air bricks in a cavity insulated wall

[Tricky Dicky]

I was looking to re-route my aerial and satellite down leads under the floo r and to save myself a bit of wall drilling was looking to pass them throug h a convenient air brick. I assumed that as in a normal cavity wall the inn er wall was open behind the air brick to ventilate the under floor space. T o my surprise I found some DPM material covering the inside of the air bric k, I cannot actually see what is there but can feel around from a convenien t loose floorboard. The DPM material is loose and can be lifted at the bott om where I can feel the inside of the air brick and the regular DPM above t he air brick spanning both walls. The house was cavity insulated by the pre vious owners and the air brick in question looks like it has been replaced at sometime as I found a broken piece of air brick in with this loose DPM. What should be the arrangement? I feel it should be unobstructed especially as there is a musty smell although no evidence of rot anywhere. Should I r emove the DPM material covering the air brick?

Richard

[mark]

Could the DPM have been placed by the installers of the cav.wall insulation to stop the insulation spewing out via the air brick?

mark

[meow2222]

oor and to save myself a bit of wall drilling was looking to pass them thro ugh a convenient air brick. I assumed that as in a normal cavity wall the i nner wall was open behind the air brick to ventilate the under floor space. To my surprise I found some DPM material covering the inside of the air br ick, I cannot actually see what is there but can feel around from a conveni ent loose floorboard. The DPM material is loose and can be lifted at the bo ttom where I can feel the inside of the air brick and the regular DPM above the air brick spanning both walls. The house was cavity insulated by the p revious owners and the air brick in question looks like it has been replace d at sometime as I found a broken piece of air brick in with this loose DPM . What should be the arrangement? I feel it should be unobstructed especial ly as there is a musty smell although no evidence of rot anywhere. Should I remove the DPM material covering the air brick?

If this is a Victorian house with suspended timber floor over earth, then y es. Otherwise we're very short on construction details

NT

[Tricky Dicky]

The house is a brick built bungalow erected in 1975, the cavity wall insula tion was put in approx. 5 years ago and is the blown wool type. One thing I did not mention was that a radiator pipe used to emerge from under the flo or directly in front of the air brick and it did occur to me that the loose DPM material was placed there to ward off wind blowing in on the pipe.

Richard

[meow2222]

lation was put in approx. 5 years ago and is the blown wool type. One thing I did not mention was that a radiator pipe used to emerge from under the f loor directly in front of the air brick and it did occur to me that the loo se DPM material was placed there to ward off wind blowing in on the pipe.

Unless you tell us the construction, how can we help?

NT

[Tricky Dicky]

The construction is outer wall brick, inner wall block construction unknown cavity width but filled with blown wool type insulation. Internal walls ar e all block construction and floors are suspended T&G on 4" x 2" joists sup ported on dwarf walls @ 48" spacing with DPM separating joists from brick w ork. Air bricks are below floor level with DPM running over the top of air bricks, inner wall has openings in line with air bricks. The underfloor is poured concrete which I am sure does not have an overall DPM layer.

Richard

[Tricky Dicky]

Just had a look at the next air brick on the same wall and it has a more no rmal situation in my opinion of a gap in the inner wall to allow under floo r ventilation and no obstructions. I am beginning to think the DPM material on the air brick in question was put in badly when the air brick was repla ced as it seems cemented in above the air brick and on one side tucked into the cavity whilst loose at the other end (sorry no photos 2 joists very cl ose to one another making it difficult without ripping up more floor boards ). I am going to cut it away and clear the obstruction I cannot see what ha rm it will do, unless someone can tell me different?

Richard

[meow2222]

wn cavity width but filled with blown wool type insulation. Internal walls are all block construction and floors are suspended T&G on 4" x 2" joists s upported on dwarf walls @ 48" spacing with DPM separating joists from brick work. Air bricks are below floor level with DPM running over the top of ai r bricks, inner wall has openings in line with air bricks. The underfloor i s poured concrete which I am sure does not have an overall DPM layer.

The space should be vented to prevent rot. I'd remove the blockage.

NT