Groundwater ingress into garage

[reluctantpaddler]

Hi
I have a detached garage, standing on a concrete slab, immediately next to my neighbours garden retaining wall, which is slightly higher.

The garage wall and the retaining wall are less than 6" apart.

After rainfall, groundwater seeps through the single brick wall at floor level, despite attempts by previous occupants to block ingress with additional mortaring. It seems to be groundwater seepage from the next property, which will gather in the gap between the walls (slab base) and then find the weak spots in the garage wall.

There is no means of access to repair the garage wall from the outside, and it's difficult to locate the weakness in the mortar joints on the inside.

I thought about clearing the gap between the walls and then either using tanking slurry to form a seal from the outside, or pouring a wet mortar mix into the gap for the same purpose.

Does this sound like a sensible solution or would I be throwing money away?

Many thanks for any suggestions.

 

[freddiemercurystwin]

Photos?

 

[reluctantpaddler]

Pics uploaded.

Nos 1 and 2 show the distance between the two walls (dark void next to the brickwork on left hand side. The stonework is the top of the neighbour's retaining wall.

Nos 3 and 4 are of the inside of the garage to show a couple of examples of what is left of the last ingress, taken today (hot dry June day). You can see it's going green with moss/algae as well.

Number 5 shows the outside taken from the opposite end. The rain channel is positioned across the top of the retaining wall and is about 4 feet above the ground level. It is possibly serving little purpose to be fair. Beneath it is a void, down to the ground where the concrete base is preventing natural seepage.
The working area is very narrow and inaccessible.

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• reluctantpaddler
• 11 Jun 2014
• 1

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• reluctantpaddler
• 11 Jun 2014
• 1

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• reluctantpaddler
• 11 Jun 2014
• 1

Untitled

• reluctantpaddler
• 11 Jun 2014
• 1

Untitled

• reluctantpaddler
• 11 Jun 2014
• 1

 

[theprinceofdarkness]

I think the first thing to do is to thoroughly clean the area finishing off with a hose, so you can see what the problem is. Water will get into that area, so can only be cleared by draining. So your hosing will find out where the water runs to. Ideally it should go straight into the ground, but it looks like your garage base was cast in, right up against the wall, so no drainage holes/gap. you could put them in your self but its a lot of work and they need to be kept clear of debris.
I would go for a fillet up against your garage wall, so the water will run outwards and away from it. If the two sides of the garage are free draining, it would be very sexy to have the fillet thick at the centre of the garage, getting thinner towards the edges, so any water that falls in this area will flow towards the sides and away from the end wall.
Because of the depth/narrowness, I would make some tools out of wood so the fillet can be formed "remotely" , Set a 6" of 3" X 1" wood on the end of a bit of 2" X 2" which is cut off at 45 degrees, giving the 6" dimension an angle so pushing it down forms the 2" X 2" fillet.
Once the area has dried out, prime the area next to the garage wall and up it with a 1:1 srbf/cement solution (old paint brush on a stick?). Follow with a 2:1 sand cement mortar mix with at least 10% srbf in the mix. Splodge it in and form with your tool (its a good job no one can see this). Should fix it, if it does not, paint on more SRBF/cement mix.
Frank

 

[theprinceofdarkness]

Another thought, after the above repair, it would be a good idea to stop debris getting into you gulley, blocking it and you having water back through your wall. Basically I am proposing that the void is filled with some loose fill or foam, such that water will drain through it but leaves etc. wont get caught in it. This is an idea that I have used, that is fill the top of the gap with a piece of wood standing on legs. I actually used a bit tanalised decking strip. If you fit it as tight as possible and stand it on legs, if you get water through again it can be lifted and the problem corrected. I would make it so its a little bit proud of the wall, say 1/2".
Frank

 

[reluctantpaddler]

Frank
Many thanks for your time and suggestions on this.
I'll be tackling this tomorrow.
Very grateful.