Not very exciting but... Airbricks, can anyone help me understand a simple concept?

[SadPander]

So... after a comment that my house has 'poor sub floor ventilation' I have been investigating the numerous air bricks on my external walls. Having taken a kebab skewer (best item I could find for the job ) I poked this through the air vent from the outside. I was assuming that this should just poke right the way through into the sub floor void, but it didn't it hit something solid. This isn't right is it?

Can anyone with a tiny bit more knowlege than myself confirm if my suspicions are correct?

Your suspicions are correct - air bricks allow a howling gale small amount of air to pass through the void under your ground floor to allow it to "breathe", this helps to prevent damp. I suspect someone found the amount of air a little too bracing and blocked them up - bad mistake.

in older houses, the cavity wall may be ventilated by having an airbrick into the cavity at the bottom of the wall, and one at the top. This keeps the cavity, and your house, nice and cold.

Air bricks are usually fitted to ventilate the underfloor void, and these should never be blocked. Sometimes they were to ventilate a pantry or food store which has since been removed, and these are often blocked.

Your skewer might possibly have hit a floor joist which may be close to the outside wall. Without taking up the floor you won't know if there is room for the air to blow under or round the joist.

Thanks lala and PigeltJohn. The house is 1900's so solid walls. Having undertaken further investigations I think that by judging the height of the air bricks on the wall that they ae too high up be be sub floor, they look as though they are roughly skirting level - which I guess isn't good! I have also had a quick poke about in the bit of sub floor I can access and can't see the airbricks from that side either, although there is no sign of rot in the timber which I thought there would be if no ventilation? Very confused!

No expert knowedge from me, but - apparently a 1910 brick built terrace house we own has no air brick in the bay window (anywhere I assume) and one is needed. Our floor joists werent rotten, but there was a fungal black mould on the wall under the bay window -cost £150
We asked for a second opinion - builder says the tenants are cooking food without pan lids on and drying clothes on radiators. He says the air brick isnt needed.
Moral of the story - much confusion!

it sounds like they may have been put in to provide fresh air for a gas or coal fire. Is there a fireplace in that room, and is it in use?

was the room formerly a kitchen?

How many of these airbricks are there?

or,

They might be Z-shaped "periscopic" airbricks where for some stupid reason the ground level outside the house has been raised, which will promote damp, and an airbrick has been fitted which has a duct so the inside orifice is lower than the outside. Is there paving outside? How high are the airbricks above ground level?

I have a question about airbricks
I recently discovered that the airbricks for the lounge have been covered up with gravel. There are about 4 or 5 and they are along the whol of the front of the house. House is 1960s
There is a channel and then the path in the garden and I removed all the gravel and uncovered the airbricks.
I have done the right thing haven't I? It is a lot draughtier in the lounge but we have woodburner and need some ventiliton, dont we?
I don't like te idea of the airbricks being blocked, after all theywere put there for a reason, right?

if your airbricks are below ground level, and are covered up, that will prevent ventilation and promote damp and rot. I bet somebody raised the outside ground level after the house was built. This is also likely to have bridged the damp course, which will also promote damp and rot. It should be dug out to reduce the ground level.

If your room is now draught I am guessing you have stripped old bare boards.

Thanks pigletjohn- I have removed all the gravel and the airbricks are now free and unobstructed.
I have carpet which is odd. It is very old though and in need of replacing, so I am guessing that a decent underlay will help the draught.

If the channel was dug next to the house and filled with gravel, could it be a (I think) French drain, dug to help get rid of damp? I will defer to PJ's expertise but I remember a builder recommending one at a house we once owned as the ground had been built up over its original level.

maybe the draught is coming under the skirting board.

french drain is to allow water away from a wall, but it should not be allowed to obstruct airbricks.

SunnyShores I symapathise with your confused state, trying to get the same opinion from more than one person seems imposible sometimes - it is hard to know who to beleive!

PigletJohn Thank you for taking the time to reply. There is a fireplace in the room, it is an open plan lounge/diner and hasn't ever been a kitchen I don't think. In the didning area there is one to the side of the house and on to the front, and in the living area there are two in the bay window, all look too high to be venting the sub floor and are in the second row of bricks (the external floor level is about equal to the internal.)

To the front of the house is concrete (would have originally been tiled I guess so this could be raised above the original level) to the side is pavement, again could have been raised over time. I think maybe these ground levels need to be lowered and airbricks fitted at the correct level, but not sure how this could be done on the side which is straight onto the pavement.

LineRunner I totally agree!

you might have to put the Z-shaped ducted airbricks in. Would need a strong, skilled DIYer, otherwise a good self-employed brickie or small builder.

Get local recommendations from friends and neighbours, it needs more care and time than building a wall.

try to find the original DPC, it will usually be two bricks above where the ground level used to be. The ground level should be taken back.

If somebody has paved next to a house it is also vital that it slopes away from the house, otherwise rainwater will flow into your walls and underfloor. A french drain might be necessary as well, you basically dig a trench next to the wall to stop wet earth or water touching the wall, and put cobbbles or large stones (not gravel) into the trench to stop the earth slumping back. These days you can use landscape fabric to line the trench as well to stop mud washing in.