Earth banked up against garage wall - how to 'tank' the wall?

[honestworker]

My in-laws have a brick garage (single brick with piers on a concrete slab - facing brick, not engineering brick). Several decades ago, the neighbours (now there's only a widow in her 80s) raised their garden level up to the height of two courses of brick on the side that catches the prevailing wind and rain. On looking in the garage, the bottom two courses of brick are damp and wet, and the mortar is wet. There is deterioration of the bricks and mortar, and anything metal on that side of the garage is covered in rust. Coincidentally, there is a DPC between the second and third courses of brick.

I have permission to scrape the soil away and expose the bricks. Eventually the bricks will have to be covered up again - it's not possible to persuade the lady to allow a separate retaining wall to be built away from the garage wall.

1) 'Tanking' - there are many products on the market - what type should I use? Brand names?
2) Should I 'tank' the bricks, then apply a membrane and tank it again?
3) If so, what type of membrane? Brand names?

It's a difficult situation as I want to rectify the problem with the minimum of intrusion into the neighbour's garden and a minimum of discussion with the elderly widow.

Help, please, as this is a new problem for me. I need to act on this before the deterioration of the bricks and mortar is any worse.

 

[Ivor Windybottom]

Honestly you're fighting basic physics and gravity, and magic tanking paint simply won't do anything. Possibly make it worse if applied to your side, as you'd be trapping the water within the bricks. You need to stop it getting in there in the first place.

Have you offered to pay for the wall that's needed, make everything tidy etc? It may be in your interests if there's no alternative.

Or, as she's in her 80's, the reality is she won't be living there for many more years. You could just wait to discuss with the next owner.

The botch answer would be to paint their side of the wall with bitumen paint before burying it again. This would probably reduce the amount of water but it won't fix it. But then the next neighbours wouldn't want to restore the soil level back down again because it would look terrible, covered in soil-impregnated black goo.

Probably your best bet for now would be to put DPM polythene against the wall and re-bury it for now. Put some 20mm gravel against it too, ideally with a way out for the water if the land allows it.

But... a garage that's below the DPC will always be damp to a degree. It will just rise up from below. You can't expect your neighbour to dig out below your floor level, garages are usually at soil level, not below. It's usually 150mm below room height - if you ever convert it then the DPM goes inside the garage, with insulation and flooring on top.

 

[honestworker]

Thank you for the reply.

The tanking would be applied to the outside wall of the garage. The garage is a detached garage, set back and the nearest corner of the garage is 10 feet away from the nearest corner of the house. There is a DPC below the slab and another DPC between the second and third courses of brick.

The concrete slab was laid correctly at ground height by the developers just after the house was built. In the decades after the garage was built, the neighbours created a raised shrub-bed by paying someone to build a 2 brick high wall on three sides and then use my in-laws' garage wall as the fourth side. This was typical of them - they had pulled other annoying strokes. I am surprised that my B-I-L did not notice this at the time (I was working away).

I am planning on the basis that it is not possible to build a retaining wall for the soil. The neighbour was extremely 'difficult' when younger and hasn't improved with age. She's in good health and might well outlast us all.

I have a roll of DPM polythene and can cut a suitable strip from it. I assume that I lay it against the wall, curl it away from the bricks at slab level with a slope for water to drain away, and then put 20mm gravel on top of it. Is this correct?

Can anyone please suggest the type or brand of tanking material to use?

All replies gratefully appreciated as I want to do this remedial work before there is any further deterioration of the bricks and the mortar. Thank you in advance.

 

[noseall]

Can anyone please suggest the type or brand of tanking material to use?

Either builders DPM or a geo-tex waterproof fabric. Neither of these will be chased into a bed joint I guess. Or if you want something robust and sturdy, chase in some lead or get a flat roofer to flash it for you.