Water ingress into airbrick.

Phil4432

Afternoon all,

Was looking at my parents driveway last night, looks like there might be some ingress in heavy rain, due to the height of the paving stones.

Please forgive all novice observations and ideas.


The driveway is  shared, 3 bed semi.  When it was installed, a builder friend pointed out that as the house was lower than the street, water was coming down the drive and hitting the side of the house.  He showed me with a hose, and said it could be a problem. 

I then paid him to build the lateral channel 4 years ago.

That's completely remedied the flow of water coming down the driveway, but in heavy rain I recently observed that the air brick is getting some ingress.  The room above it is the downstairs bathroom, and I have been noticing a slight intermittent smell in there.  I'd describe the smell as a dry, dusty smell, but not musty.

The driveway has raised the ground level, and I'm not sure what the installers were thinking.  Indeed, the neighbors house has had rising damp a couple of years after the installation of the driveway which I'm keen to avoid. The houses are on clay.

What would be the best way to increase the gap between air brick and ground?  The lateral drain channel being right next to the house would solve the ingress, but I don't believe that would deal with splash back from rain as the grating only reduces the amount of surface area by about 40%. 

My ideas are;

-Having a drain channel right next to the house and sunk so that its lower than the driveway might work, but would look very odd.  Also, water falling over the 'lip,' of a higher paving stone would actually create additional splash back?

-Have a French drain or 'splash strip,'(same thing?)  next to the wall.  Don't feel a French drain by itself would have been a solution, as there is so much water coming down that drive.  So maybe gravel/French drain next to the wall to the inside of the existing channel?  So then it would be drain channel, red stones and then gravel.

-Just dam or box off the air bricks, as seen in the picture at the bottom of this page.  https://www.pavingexpert.com/splash_strips
  That's the cheapest option and would solve the ingress to the air bricks.  Most of the airbricks to the house are too low, so that could be done to all of them.  The neighbors had that to their airbrick.
   But this wouldn't deal with the splash-back.  Not actually sure if the splash-back is actually a problem but the rise of the level of the drive means that the dpc is not at the recommended 220mm.

I've referred to this page also  https://1stassociated.co.uk/articles/french-drains2.asp

As I write this, I get the feeling that the most thorough solution would be a French drain all around the house, with the airbricks boxed in.  Very much open to suggestions.

FreeBear

A French drain would certainly help - A fairly low cost modification that you could do yourself with one proviso....

The linear drain and first course of blocks need to be set in concrete or you will find the drive will start to "move" and the gaps between the blocks start to open up.

Did the builder install any soakaway when the linear drain was fitted ?

If he didn't, then that needs to be rectified.

Phil4432

FreeBear said:

A French drain would certainly help - A fairly low cost modification that you could do yourself with one proviso....

The linear drain and first course of blocks need to be set in concrete or you will find the drive will start to "move" and the gaps between the blocks start to open up.

Did the builder install any soakaway when the linear drain was fitted ?

If he didn't, then that needs to be rectified.

Thanks mate.

Current linear drain goes directly into gutter and works a treat.  Can handle large amounts of water and seems solidly built.  Its just the area between the drain and wall.

Phil4432

Is this a good way to protect an air brick from water ingress?



A neighbour has had this done, wouldn't the ground just below the air brick fill up with water?

Cheers...

FreeBear

Put some gravel in the bottom of the dam and any water that collects should drain away. Just don't fill it with concrete unless you install a pipe to drain the water away.

Phil4432

FreeBear said:

Put some gravel in the bottom of the dam and any water that collects should drain away. Just don't fill it with concrete unless you install a pipe to drain the water away.

Forgive my ignorance, but where would it drain to?  If its on clay, wouldn't it just overflow until the clay absorbed it?

FreeBear

Phil4432 said:

FreeBear said:

Put some gravel in the bottom of the dam and any water that collects should drain away. Just don't fill it with concrete unless you install a pipe to drain the water away.

Forgive my ignorance, but where would it drain to?  If its on clay, wouldn't it just overflow until the clay absorbed it?

Even clay will absorb some water. But if worried, pipe the water off to a soakaway (and do the same with the french drain).

Phil4432

Looking at the new drives in the area; most have risen the original surface and are much closer to the air bricks.  Some of the new ground levels are actually on the air bricks.

One I looked at has the drive sloping, so water gets channeled right into the air brick.  Crazy.