Moisture coming through garage wall that borders neighbours flower beds

[EdZ3]

Hi, I have a fully detached double garage where one wall borders our neighbours garden. On the neighbours side of that wall they have a flower bed with creepers and plants growing up the wall. I have a serious damp issue on that wall with moisture coming through from not just the bottom but also much higher up in the wall. I get on well with the neighbour and don not wish to ruin their garden so I need to find a solution that preserves the neighbours plants. We had great success using Larsen Universal DPM in our hallway to remedy a minor damp issue in the floor. It seems like the kind of product that might do the job for my garage wall but Larsen felt it was really only for floors.
Was wondering if anyone had any advice or could suggest an alternate that might help solve the problem?

Kind regards,

Steve

 

[freddiemercurystwin]

If it's damp above the height of the planter then it suggests another issue or perhaps in addition to the problem with the planter.

 

[EdZ3]

Well the plants are a mix of creepers and very tall ones so some are attached to the wall. I'm guessing the moisture above the planter is from when they water the plants. There are other issues in the garage, one being that there is no proper dpm on the floor and moisture from the floor is particularly bad in wetter months but the bordering wall seems to me like a separate issue. Just really wondering what the best way to approach this would be?

 

[Harry Bloomfield]

If the wall is your property, as it would seem to be, explain to your neighbour the issues he is causing and ask him/her nicely to clear all the soil and growth to at least 3" below your DPC level.

 

[EdZ3]

as previously mentioned, I'd rather not go that route as it would likely mean the neighbour tearing up their flower beds. It also isn't just damp at the base of the wall, theres moisture high up sometimes too which makes me think is from them watering the plants.

 

[Harry Bloomfield]

It also isn't just damp at the base of the wall, theres moisture high up sometimes too which makes me think is from them watering the plants.

There really is no other way forward, than reducing the level of the soil and stopping the watering soaking the wall.

 

[George_engineer]

Is it a cavity wall or a single skin brick(maybe only half brick thick)?

 

[robinbanks]

There really is no other way forward

Make that wall of the garage a cavity wall with a drainage channel at the base

 

[EdZ3]

Its not a cavity wall, the wall is brick about 20-25cm thick. I had looked into the drainage mats route - I figured it would mean me having to add a drain to the front of the garage and tap into our main drainage system as the closest manhole is 5m from the garage front.
I was really hoping there might be a simpler option of a paintable waterproof membrane I could apply to the wall and then stud on top of that and cover with insulated plaster board. See any issues with this route?

 

[^woody^]

If you can, have the plants pulled forward or wait until autumn to allow the external face to be coated with a quality silaned based water repellent.

Polythene DPM draped down the wall and channelled in to the DPC. Then fix your dry lining.

However, if the inner face is streaming with water, and you can't coat the external face, or if that does not reduce the ingress due to the covered lower part of the external face, then you'll need a drained cavity and either a way of moving collected water or extra ventilation to evaporate it.

You only need a small soakaway for drainage, not a drain.

 

[EdZ3]

I feel like moving the plants is a total last resort for us as it would involve significant damage to the area to get the job done. The wall on the neighbours side is pebbledash and covered in a few layers of white exterior emulsion. We've already removed the paint from our own side with a needle scaler but it was about 2-3 days work just to do the equivalent sized wall - noisy, messy and fairly invasive. I understand its the neighbours responsibility not to cause damage to our side but If we could achieve a good result by working on our side only it would be preferable. To be clear the wall on our side is certainly not streaming with water, it just displays damp patches from top to bottom, primarily at the bottom, but nothing where water is lying thick...just that if I leave wood lying against that wall it will look damp in a while. From what I can tell theres no DPC or DPM. Its an issue I like to solve permenantly before we undertake any additional renovation work.

Larsens had suggested Larpruf CG which is a cementous tanking slurry but I'm worried expansion might cause problems with cracking down the line: https://larsenbuildingproducts.com/product/larpruf-cg/

Regarding the drained cavity method - you think this would work with a stud wall in front of current wall or are you suggesting I build an additional brick wall to create the cavity?

 

[^woody^]

Rendered?

Your problem is that if you coat the inner face with anything, the wall is not going to dry out. This will tend to then either blow the inner or outer coating.

As this is not significant penetrating damp, you may be better just lining it on battens fixed to the wall, and allow a vented cavity for evaporation.

 

[Harry Bloomfield]

As this is not significant penetrating damp, you may be better just lining it on battens fixed to the wall, and allow a vented cavity for evaporation.

If its wet, the battens will quickly rot.

 

[^woody^]

If its wet, the battens will quickly rot.

Treated. Polythene backed.

 

[EdZ3]

That tanking slurry I mentioned is specifically designed to apply to waterproof from the inside no? Its intended for use in basements etc and is applied before render so it seems like it shouldn't blow.

Regarding the battens, that was also my concern that they would eventually rot if fixing screws were to penetrate any membrane on the offending wall. I had thought if I could coat the wall in a liquid waterproofing membrane I could thistlebond the wall and dot & dab insulated plasterboard on top thus removing issue of puncturing any membrane. I guess it would just mean I could never fix anything to the wall