Thread: Adding a few mm to the concrete pad for my wooden gas meter enclosure

I've just finished a project where I renovated an old gas meter enclosure. BAA0C251-BACF-48D0-AB49-9CB3EDC7DDBE.jpgThis mainly involved replacing the rotted lid and some removal of rotted wood from the weatherboard sides and repair with builders bog. Here's the finished job. FD71C2F9-D2A3-4AA6-A746-251CD61F1442.jpg Here's what the inside looks like with extra ss angle supports 3F58A9A6-6E36-4291-A0C1-F9CD8C8CD35A.jpg, but the main fixing was with dadoes which I aligned using four dowels to the frame and glued to the base: 270EE558-D212-40F5-90C0-83CDE78C7CA5.jpg. I then did two coats of undercoat and two of Weathershield.

Anyway, back to finishing the job. The enclosure rests on the left hand side on loose concrete blocks (there needs to be access to gas pipes beneath them) and on the right on a concrete slab. See picture:0CE36B70-B19E-4DC2-A5A3-96EFB7A70066.jpg

However, if you look at the second picture above, you'll see that the finished enclosure is not resting on the blocks. It's being held up in space by the gas vent pipe (coming out of the enclosure top left). To level it, I could cut a hole in the frame to allow the pipe room, or get a plumber to shift the vent pipe down, but the neatest solution seems to be to raise the concrete base 10-12mm. On the LHS this is easier, and I just add more soil fill below the blocks. On the right hand side I need to add quick set cement or maybe a couple of Villaboard sheets onto the existing slab to add the extra mm. I've had problems in the past with adding thin cement and getting it to stick, so I'm leaning towards the latter. Any recommendations?