Damp issues in garage

[whitty28]

Hi all,

I am after some advice with regards to damp in my single skin detached garage. I have had a damp survey done and it confirmed that I have damp bridging into the existing concrete slab floor from the engineering bricks below the DPC. Apparently fairly common in garages. No visible signs of any DPM under the existing concrete slab. The single skin does have a DPC, which is 150mm above ground level all the way round the garage.

My goal here is to convert the rear two thirds of the garage into an office, and have the front third as my workshop. So I want any damp problems fixed before I plough money into the conversion.

I have attached a few photos of the garage and current damp issues. I have also detailed the problem in a drawing, and provided 2 possible solutions.

Solution A: rip the existing concrete floor up, install a physical dpm, lapped into the same mortar joint as the DPC. I don’t even know if this is possible, given I’d need to rake mortar out of an existing wall to lap the new dpm with the existing DPC, and I think it’ll also look pretty poor as a finish.

Solution B: use an epoxy dpm painted on the wall up to the existing DPC, and around 150mm into the floor. Cheaper, better finish but potentially traps the moisture into the slab and not sure if it will solve the issue long term.

I am after a review of the solutions and any advice from people who have attempted this or something close to this before.

Thanks in advance.

 

[23vc]

If the new bits habitable, you’d likely want the floor level higher, and more like level with the wall dpc, so treat existing garage floor as a sub base layer and go on top with floating celotex or another slab/screed. Dpm could just lap up the walls a bit rather than necessarily being chased into the wall.

 

[whitty28]

@23vc thanks for the quick reply.

Understand where you’re coming from, and that would be the plan for the rear 2/3 which will be habitable (office spaces used 8hrs a day).

But the problem will still remain in the front 1/3 portion (workshop), if you catch my drift.

 

[23vc]

You’ve got limited options with a single skin wall and an inside floor level the same as outside, due to surface water just going sideways from outside to inside. Depends if you need the level threshold at the garage door