Block paving blocking airbricks

The previous owners of our house put block paving in on the original drive and created a new section of drive that previously had been garden. Matching the levels with the drive meant that whoever put the block paving in just blocked across the airbricks, partially blocking them in some places and completely blocking them in others. They also got the fall wrong, with the slope being across the drive, but also slightly towards the house.

I had to lift the floorboards recently to move a plug socket and noticed water was actually running into the floor void through one air brick which had been completely covered by the block paving, so i need to do something to prevent this from happening.

I could remove the blocks around the airbricks to create pockets and then line the pocket with cement. I'd use clay tiles around the perimeter of the pockets to act as a dam to stop water flowing into the pockets. That would sort the problem but feels a bit of a bodge and always be at potential risk of the pockets filling with debris or water in very heavy rain. I've also seen the anti flood type periscopes that raise the height of the airbrick vents, but they're surface mounted, unsightly and would look odd on the front of the bay which is quite visible. I don't really have the option of periscope vents in the walls themselves as it 's a 1920's built house with solid walls so no cavities to put the vents into. Nor do i have the option of raising the airbrick up a course as the airbricks are directly under the floorboards.

Is there a better way of doing this other than what i suggested above?

Comments appreciated.

Pics below:
Partially blocked airbrick

Fully covered airbrick

The airbrick that was fully covered and letting in water where i've lifted the blocks to expose it and have put a couple of piece of tile in front to prevent sand falling into the airbrick.

Yep that needs to come up. As you've turned your air vents in to drains. You might be able to fit a telescoping vent otherwise you need to lift the bricks and fit some sort of lip to stop the rain going in (as you say).

I suspect you have non-waterproof electric cables to worry about too?

Lower said:

Is there a better way

Click to expand...

french drain beside the house.

Dig well below the airbricks

refill with cobbles or large pebbles which allow draining and do not support damp by capillarity.

pull them back to fully expose the airbrick grille.

surely that would drain in to the foundations? Or are you proposing to route the water away from the house via the drain?

motorbiking said:

surely that would drain in to the foundations?

Click to expand...

only the water that currently drains into the airbricks.

which is worse.

The same will happen if you just close off the airbricks or fit periscope vents. The French Drain is a better solution than either of them.

The french drain can be led away from the house to some convenient soakaway, pond, or lower ground, if as I understand, the drive has been foolishly laid to lead rainfall to run towards the house.

Its a good solution if you can route it away somewhere, even if its just a small soak-away. The other option would be a grid hopper, as the French drain will increase the drain area. Though if its sloping to the house it would be needed.

You could raise the air bricks albeit a bit of work, I did something similar a while back on a job.

JohnD said:

only the water that currently drains into the airbricks.

which is worse.

The same will happen if you just close off the airbricks or fit periscope vents. The French Drain is a better solution than either of them.

The french drain can be led away from the house to some convenient soakaway, pond, or lower ground, if as I understand, the drive has been foolishly laid to lead rainfall to run towards the house.

Click to expand...

Thankfully, the fall towards the house is very small, and the overhangs from the roof very large we don't get water pooling against the house. It soaks into the sand base of the block work drive and then a very small amount of water weeps its way in through the air bricks.

The fall issue i could fix with a strip drain, but i'd still have the airbrick problem.

It's occurred to me that i could make my own periscope air brick that would essentially be a steel box one brick deep but two bricks high with a grill at the front in the top half and an opening at the back lower half. I could then remove each airbrick and the brick above, and insert the new periscope. I have the facilities to make my periscope airbricks out of 6mm steel and could get it galvanised and then painted black. You'd only really see the grill at front as the bottom half would be obscured by the block paving but the grill would be raised above the block paving level and also be flush with the wall. I could then insert a strip drain quite tightly to the brickwork without needing the pockets in front of the below ground level air bricks.

The bricks i'd have to take out are blue bricks and from previous experience, solid as rock. In order to do what i've suggested, i'd have to cut the blue bricks above the air bricks due to the bond. Where you can see a half brick, is that likely to be an end on brick forming the bond in the solid wall?

freddiemercurystwin said:

You could raise the air bricks albeit a bit of work, I did something similar a while back on a job.

Click to expand...

Don't think i've got the depth of wall to be able to fit a proprietary periscope vent. Hence my thinking i could do the same with a two brick high steel fabricated box with a grill in the front top half.

Lower said:

The bricks i'd have to take out are blue bricks and from previous experience, solid as rock. In order to do what i've suggested, i'd have to cut the blue bricks above the air bricks due to the bond. Where you can see a half brick, is that likely to be an end on brick forming the bond in the solid wall?

Click to expand...

To make a French drain, you do not take any bricks out of the wall. You remove the paving next to the wall, and dig out the sand and other material, to get back to about where ground level used to be when the house was built, plus a bit.

It's this badly installed extra paving to a higher level that has caused the problems.

Personally I wouldn't take any chances with a solid wall, questionable (by virtue of age) dpc and old timber floor. Reduce the entire perimeter ground level to 150mm below the DPC level - they were built like that for a reason.

JohnD said:

To make a French drain, you do not take any bricks out of the wall. You remove the paving next to the wall, and dig out the sand and other material, to get back to about where ground level used to be when the house was built, plus a bit.

It's this badly installed extra paving to a higher level that has caused the problems.

Click to expand...

I agree its the extra paving that's been installed at the wrong level that caused the problem and something i intend to address in the medium term. However, it'll be part of a much bigger job to move the whole drive to create a much bigger off road parking and garage area, and that'll allow me to reinstate garden in the current position and lower the ground levels.

I need a solution that will resolve the problem for the next 5 or so years, but that can be left permanently.

I understand the difference between the french drain and my home made periscope option, i just don't think i need the french drain for two reasons:

1. There is no damp problem within the walls, thankfully. The blue brick course is above the block paving and there is minimal splashing on the walls due to the large roof overhangs.
2. I plan to install a strip drain in the block paving to catch the water that runs towards the house that only really happens in very heavy rain or when i wash a car.

The ground around the house i also heavy clay, so i'm not sure how well a french drain would work.

In the short term, there isn't the space to lower the ground level all around the bay as it would encroach into the entrance pathway. Creating pockets for the airbricks would cause a similar problem, hence wanting to find a way to lift the airbricks, but ideally flush to the wall.

cdbe said:

Personally I wouldn't take any chances with a solid wall, questionable (by virtue of age) dpc and old timber floor. Reduce the entire perimeter ground level to 150mm below the DPC level - they were built like that for a reason.

Click to expand...

The floor itself is actually independent of the wall. Whoever built our house built separate dwarf wall to act as bearers for the joists.

I'm not nervous about taking red bricks out, but cutting an blue engineering brick in half would be hard work, particularly taking the end off a blue brick if its end on into the solid wall. The only way i could see to do it would be to chain drill it as much as possible to the right depth, and then smash it out.