Very damp/wet garage

My problem is with my brick-built garage that lets in water and/or is damp. I can't really see where the water is coming from but it collects on the floor working in from the side walls when the rain is heavy. Here's what I know...

- the construction is single-skin brick on a 150mm reinforced concrete slab. I have the plans and they claim that there is a DPC. The middle part of the slap remains dry so I don't think it's coming up through the floor.
- it was built about 20 years ago
- The brickwork and pointing is all in good condition as is the pitched, tiled roof. The gutters have been cleaned and the drains... well... drain.
- It has what I think is called a 'french drain' right round the outside (perforated pipe buried in gravel)
- it is in an exposed location at the top of a hill in Scotland with nothing but fields to the rear. It's the exposed end that gets wettest.

My thoughts are that the water is percolating through the bricks although there's no visible evidence (no water running down the walls or anything).

Is it worth trying something like Thomson's Water Seal... or something else... or is more investigation needed?

Any thoughts much appreciated

 

Outside the wall there is concrete but it gently slopes for a few inches towards the french drain...



Here are a couple of excerpts from the plans...

 

So... the cure is?

...or, even better, is there any way to prove it with (I'm guessing) drastic remedial action?

 

The scrapy line at the bottom (hard to photograph in the dark and wet) is the edge of the concrete - I scraped back some of the mud. You're right, it's up the side of the bottom brick.

 

I'm not sure if it's the done thing to 'bump' but has anybody any more ideas/help at all. Getting a bit desperate as stuff is getting knackered due to the wet/damp

Thanks!

 

Great... that's what I'll do then.

If that works - is there likely to be a benefit in painting the rest of the brickwork with a sealant (Thompson's WaterSeal say)? In an idea world, I'd like to get it as dry as I can.

Thanks for the help

 

Ok... I'll see how I get on with the black stuff. Appreciate your help!