So…we inherited a greenhouse that is sitting on a concrete slab; it does not seem to be fixed to the concrete. When it rains, the water seeps under the wall and into the greenhouse. I should mention that we live in Scotland so rain is not rare! The people we bought the house from had tried sealing the outside between the wood and the concrete with caulk but to no avail. I am concerned both that the wood will rot and the floor gets wet.
I am considering either putting a rubber seal (like they use under garage doors) under the wall or just lifting the greenhouse up an inch or two using pieces of stone to create a gap. The former feels like it *might* stop water getting in and protect the wood from standing in the water. The latter seems like it will let the water in and back out so the wood will be protected and I can just power wash the concrete at the end of each season.
Would love the hive mind’s thoughts on either of these or another better option.
Thoughts? TIA!
by chapmaa
4 Comments
Do you have, or could you install, gutters or downspouts on the building to help direct water away? If that’s not possible a stone base with mortar sounds like a good option.
Ideally, id remove the concrete and put in blue rock so you would have good drainage.
The problem I see with a seal and caulking, is leaks, and the wood on the outside would still be exposed to lots of water and rot.
Therefore I would just raise it up higher. I’d raise it up and float it. They have this material here in the US that is made from recycled rubber that you can get up to a 1” thick solid mats that you can cut to width and insert it under the perimeter of the wall to keep the wood above the water drainage level. I did this for a cedar gazebo I installed on a concrete slab. The wood sits above the water line so it does not rot.
Had a slab built for the base of my greenhouse and it’s much the same I’m also in Scotland. The issue is concrete is porous and most slabs laid for outdoor buildings don’t have a sheet of damp proof membrane under them at construction. By all means lift the wood off the concrete and put plastic between the two as it might help but tbh that timber looks treated or it would be rotting. For the concrete slab though you get water proofing treatments. I put one down and the issue in summer is water pooling or not draining because of treating it. For me water ingress in winter when I’m not growing much is not a big issue. In summer pooling can help green algae from. It also isn’t great when I’m having to water the plants and there is nowhere for it to run off.
I don’t know about availability in your area, but I would lift it and place concrete pavers under the greenhouse. You will still get water ingress, but the frame wouldn’t be sitting in water. And a little water inside a greenhouse only helps the humidity.