Very damp retaining wall

[IrritableBitchSyndrome]

Hi, does anyone have any experience of dealing with a very wet retaining wall? The wall which forms the bottom half of our carport, which is below the level of our neighbours garden, is very wet, covered in moss, and some of the bricks are crumbling. Does anyone know what can be done about this, and what kind of firm would be able to help?

Not sure if this will help but have you checked if the guttering/down pipe outside the wall is working and not blocked as ime water pouring down an exterior wall can cause terrible penetrating damp, if that's the issue fix the gutter then the wall should dry and can be repaired by a builder.
If it's not the gutter then google damp companies in your area who can help.

you mean a retaining wall which has earth piled against it?

Of course it will be wet, from the damp soil. it's an underground wall, on one side at least.

You could build another wall just inside it, with DPM and ventilated drained cavity, which would look nicer.

Or you could demolish it, digging out the neighbours' garden and backfilling with pebbles going down to a French drain, and build a new wall, though your neighbours may not agree.

Tanking won't work.

Pigletjohn how wet should it be though? Neighbours further down the hill have similar walls that are not wet, which is leading me to believe ours is a problem.

The neighbours have block paving the other side of the wall, and the lady next door is very elderly and inform and relies on using her back door to get out of the house as the front door has a step. I suspect her back door would not be usable if we were to do this so it would be an absolute last resort.

I'm not fussed about it looking nice. I quite like the moss. I'm worried about it giving way and ending up with a carport full of next doors garden.

Infirm. Not inform. Flipping autocorrect!

It sounds like the bricks are spalling. This will be due to being saturated with water and freezing. Maybe the paving slopes towards tour wall and channels rainwater.

you could demolish it and have it rebuilt in special dense bricks. Depending where you live, these will either be dark red Accrington type, or dark blue Staffordshire. If you look at some railway bridges you will see them. You need a fairly experienced professional bricklayer, who will be familiar with the method. Include weep holes for water to escape.

The bricks are more expensive than commons, but I doubt you will be using very many.

For a proper job you will need to dig out the base of the old wall and pour a concrete strip foundation. Retaining walls are prone to being pushed over by the weight of wet soil.

Experimentally, you could drill some 1" holes near the base of the wall and see how much water drains out.

p.s.

Where does the gutter from your carport roof drain to? Perhaps it is contributing to the problem.

I suspect leaky guttering is contributing. Is it possible to demolish and rebuild a retaining wall without damaging the neighbours garden, or is that wishful thinking?

Also, thanks for your advice PigletJohn and GoldAngel. Much appreciated.

yes, but it depends how tall it is. Consider digging a trench in the garden, it will stay in shape for a while before collapsing.

It's possible to do it in alternate bays, say a metre at a time, which prevents the whole garden slipping out. It also depends what the soil is, and how wet. Wed mud has little stability. If the height is only a foot or so you can support it with thick ply, held up with wooden or metal stakes banged into the ground, and build the new wall up against the ply, leaving it to rot.

Any cavity between the old ground and the new wall should be filled with granular material which will aid drainage and prevent the ground sinking into the cavity. You can also tack dpm against the support to reduce water penetration, provided you also provide a route for it to escape. This will not prevent all damp though, since water will also push up into the wall from below.

It's heavy clay, with a nice brick driveway on the neighbours side, and the wall is around a metre high. I've left messages with a few local structural engineers in the hope of getting someone to have a look. Will also get the gutter checked out.

Argh! Have remembered there is a flipping prefab concrete garage the other side too for part of the length. Sigh!

Hi, just wondering how it went? Did you manage to get it fixed in the end? Cheers

Also wondering here! @irritablebitchsyndrome

Hi, Sorry, I'm a bit confused by your reply. Are you still trying to get a tradie to take a look?

Sorry, @Noconsent, ignore my last comment. I thought your comment was written by @irritablebitchsyndrome.

Hi, sorry I didn't come back earlier! I just found this post while searching the internet for the same scenario as my original question! As you may have guessed, it's not resolved yet, although advice from a structural engineer was that the wall would be fine for at least 15 years.

Also the gutter isn't fixable due to the angle. Might just get the carport demolished and rebuilt properly...