Damp proof course and raised external floor

[rborob]

Hi all,
I recently moved into a house which had had a new driveway put in. This caused the external floor to be higher than originally thought. The builder had built the wall flush to the wall half covering the vents with a plastic gutter. This became an issue on the survey as they raised the fact that heavy rain would cause water to flow over the gutter and straight into the vent. He then moved the gutter back and lowered the ground level leaving a valley between gutter and vent.

Fast forward to last night's heavy rain and water pooling in the valley. The owner had put stones in which I think could have been stopping the water from draining, but I guess I'm after advice on whether this setup is working as it should or whether I need to take action to waterproof my property.

Any advice would be greatly appreciated

 

[Mr Chibs]

It's going to pool, as it's looks like concrete under 'token' slate.
Really this needed to be removed. I'm sure a rough rule of thumb is there should be a minimum of two bricks below the DPC, before ground level.

How bad was the water?

 

[rborob]

It's going to pool, as it's looks like concrete under 'token' slate.
Really this needed to be removed. I'm sure a rough rule of thumb is there should be a minimum of two bricks below the DPC, before ground level.

How bad was the water?

It came to the first hole in the vent...i only noticed it by accident and so moved the slate out the way, after that the level seemed to drop causing me to think the slate was the issue

 

[Mr Chibs]

Proper job would be to remove the concrete, but this will probably dislodge the drain, so you'll have a larger job on your hands. If you managed to remove the 'crete' and could see soil, you could fill back up with large stones/gravel. Not sorting the problem, just living with it.

At the risk of a bodger alert...
If, in heavy rain, the channel drain is not full to the top, perhaps you could drill some holes (or cut some slots) at the bottom of the 'valley', into the side of the channel drain, this may stop the pooling.
Not an elegant solution.

If the drain is overwhelmed, it's back to the drawing board, me thinks.

 

[rborob]

Proper job would be to remove the concrete, but this will probably dislodge the drain, so you'll have a larger job on your hands. If you managed to remove the 'crete' and could see soil, you could fill back up with large stones/gravel. Not sorting the problem, just living with it.

At the risk of a bodger alert...
If, in heavy rain, the channel drain is not full to the top, perhaps you could drill some holes (or cut some slots) at the bottom of the 'valley', into the side of the channel drain, this may stop the pooling.
Not an elegant solution.

If the drain is overwhelmed, it's back to the drawing board, me thinks.

Thanks. Believe it was "torrential" rain last night that caused the increased level. (couple of walls in the street up the road collapsed due to this). I'll scrape out all the slate and sludge and see where that leaves me. Might try and chisel out the bottom of the valley in the hope i can see the soil like you said. Part of me thinks the original solution of the drain flush against the vent would have been fine

 

[Mr Chibs]

Quick thought, perhaps the channel drain could be moved away from the house? I See you could move it a course or two up the drive (design depending)

Then you could gravel in between the house and drain.
Possibly a land drain could be installed here, if you wanted to go the whole nine yards.

 

[^woody^]

No water should be getting to that slate if the surface drain was doing its job. Is it connected to a drain or the end just going into the ground?

But if that is concrete below the slate, then it would only need breaking with a chisel (some alternate holes up against the house wall), to allow water to drain through, not fully removing. It would then still function to retain the drainage channel from moving towards the house. Dont fully remove it.

 

[wessex101]

What do the airbricks actually do? Is it sub-floor ventilation, cavity ventilation etc?

 

[^woody^]

What do the airbricks actually do? Is it sub-floor ventilation, cavity ventilation etc?

Don't you know?

 

[wessex101]

My psychic powers are on the blink today.

 

[^woody^]

Oh, I thought you were asking what air bricks do.

Anyway, they tend to let air through so it dont matter what is on the other side. HTH

 

[rborob]

No water should be getting to that slate if the surface drain was doing its job. Is it connected to a drain or the end just going into the ground?

The heavy rain paired with the wind meant the rain was just "raining" into the valley which is why I believe its only come to light after the bad weather. I think theres a fair amount of smaller slate pieces causing the water to not drain out the end, so maybe removing the slate will allow it to the freedom to drain off?

 

[wessex101]

But if the airbricks only ventilate the cavity it doesn't really matter if there is standing water, it wont do any harm. If the airbricks go right through the wall to ventilate a sub-floor void then technically the void could flood. The spacing and size and position in relation to the DPC does not look like sub-floor vents hence why I asked the question.

 

[^woody^]

I can't imagine that direct rain alone would fill that volume of trench in that location. Are you sure that the surface drain was not overloaded?

 

[^woody^]

But if the airbricks only ventilate the cavity it doesn't really matter if there is standing water, it wont do any harm. If the airbricks go right through the wall to ventilate a sub-floor void then technically the void could flood. The spacing and size and position in relation to the DPC does not look like sub-floor vents hence why I asked the question.

You would not want water in a cavity to raise humidity levels in any case.

Air bricks in that location would typically be for the under floor venting or radon