Replacing airbricks for sub floor ventilation

kevsta · 13 Oct 2010

I have an semi detatched house built in 1912. There is a sub floor below the two reception rooms. Now the question is should I replace my existing clay air bricks for the newer plastic ones and increase the size while I'm at it.

Currently there is; 2 at the front of the property at 9x6, 3 along the side of the property 9x3 and two at the rear of the property also 9x3.

What do people think?

K

r896neo · 13 Oct 2010

Why do you want to? have you had problems with rot or infestation that makes you think the current ventilation is not adequate?

No point creating work for yourself if it's not solving a problem?

^woody^ · 13 Oct 2010

Changing the car or telly every few years may be OK, but it's not the same with airbricks

kevsta · 14 Oct 2010

r896neo said:
Why do you want to? have you had problems with rot or infestation that makes you think the current ventilation is not adequate?

No point creating work for yourself if it's not solving a problem?

Had a survey on the house when I bought it and it was reccomended. Also if we've been away for a few days the house does smell a bit musty in the wetter months.

Cheers

K

r896neo · 14 Oct 2010

In that case i guess it's up to you.

Surveyors sometimes suggest work like this as a precautionary measure as even though it may not be needed it is relatively cheap and easy to do. Frankly without backing it up with a reason as to why he/she thinks this work is neccassary i would ignore it because if they have found signs of damp at low level then that would be mentioned.

Whilst i don't doubt your feeling that the house is slightly musty during wet months i don't think this is anything to do with poor sub-floor ventilation, more likely poor house ventilation because people don't open the windows when it's cold and damp.

Nige F · 14 Oct 2010

kevsta said:
r896neo said:

Why do you want to? have you had problems with rot or infestation that makes you think the current ventilation is not adequate?

No point creating work for yourself if it's not solving a problem?

Click to expand...

Had a survey on the house when I bought it and it was reccomended. Also if we've been away for a few days the house does smell a bit musty in the wetter months.

Cheers

K

I`d check that the ones you have actually go through into the underfloor void - Mine didn`t in the old house we`re in now

some went through a convoluted route and others just made the cavity freezing cold

. Easy enough job if you`ve got floorboards , to lift a couple and check it out .

gregers · 14 Oct 2010

if you really need new air bricks,then go for the plastic type,as there roughly 65% efficient compared to the old terracotta airbricks which iirc are about 6%.

hotrod · 14 Oct 2010

gregers said:
if you really need new air bricks,then go for the plastic type,as there roughly 65% efficient compared to the old terracotta airbricks which iirc are about 6%.

Eh? Can you elaborate on those figures gregers I would like to know more? I use the clay terracotta airbricks everytime over the plastic type for both aesthetic and performance reasons. I think the plastic type look cheap and nasty and how many times walking round new builds do you see them caved in where someone has just kicked them by accident or knocked them with a shovel?

gregers · 14 Oct 2010

well they were the type we used to fit when i was invovled within the preservation industry,the reasoning about the clay 1s is when looking through the holes they get smaller,as they are fired they shrink so the they are not as efficient as they really should be.
we used to fit 9x6 plastic 1,s,i do agree to a point about them not looking as nice,but if the homeowner is having damp/rot problems then surely you would agree that if a job needs doing then make sure you fit the correct material to ensure the job is not a wasted 1 for the customer.

obviously the only way to ensure 100% airflow is to leave a bloody big hole,

.
we used to make sure they were well pugged in,i still see a houses in my area that i worked on without any problems and that was over 18 years ago.

stuart45 · 14 Oct 2010

A 9x6 terracotta air brick gives about 7.5 sq in ventilation, while a plastic one gives about 20 sq in, so there is quite a big difference.
Old houses had much less underfloor venting than the newer ones, and old air bricks often block up over the years.

hotrod · 15 Oct 2010

Cheers for that Stu. It is a big difference (although no where near the % differential gregers was citing above (6-65%)). It's still ~ 3 times the flow which I would never have guessed. Still, clay air bricks for me - just whack a couple more in!

Interestingly, (no, realllllllllly

) Hanson's rectangular holed air bricks give 2x the flow compared to the square holed that I usually fit (my merchant stocks both but I think the square holed look better). Never stopped to think about it.....

http://www.heidelbergcement.com/uk/en/hanson/products/bricks/brick_specials/air_bricks.htm

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Replacing airbricks for sub floor ventilation

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