Hey,
I just bought a house with a garden shed installed on top of a concrete slab. It’s one one those corrugated steel ones with good space, so I planned to use it as storage for luggage, Xmas decor, etc. I’ve now realised it’s not waterproof, so I followed the advice of another post and bought Sika Sikaflex 11FC purform to try to seal the bottom and maybe 2/3 of the top sides (keeping one for airflow). However, the floor surface is uneven and one corner seems to be on dirt, rather than concrete. I’m not sure how I can seal it or if I should only raise the floor with some pallets hoping that will keep moisture away.
Any recommendations?
Hi @linasuarez13,
Welcome to the Bunnings Workshop community, it is fantastic to have you with us.
Unfortunately, sheds are not generally designed to be completely waterproof in the same way as a home. A rebated slab edge, where the shed walls sit below the level of the internal floor, is typically needed to create a reasonably watertight installation. As your slab does not have this rebate, wind-driven rain can find its way beneath the bottom channels.
Sealing the bottom edge of the shed from the outside can still make a significant improvement. Have a look at @MitchellMc ’s step-by-step guide How to waterproof a shed floor, which explains how to use aluminium angle and sealant around the external perimeter.
This method would do a lot of good, however it is not going to completely stop water all together because you have cracked and degraded concrete, and by the sounds of it, missing sections, that will let water in.
You could pair it with something like Mitchell built in How to install a shed floor. This raised floor method could work well alongside the aluminium angle and sealant shown in the waterproofing guide. The external sealing helps prevent water from entering beneath the shed walls, while the bitumen-coated timber frame and raised Yellowtongue floor provide an additional layer of protection by keeping the finished floor above the concrete slab and away from any minor moisture that still finds its way inside.
Let me know what you think and if you have further questions, please don't hesitate to ask.
Jacob
Hi @linasuarez13
The shed looks in good condition so why not unbolt it and move it out of the way while you cut out the old concrete and pour a new slab. You can then bolt it back down with sealant under it and then seal round the bottom edges.
