How to ensure shed ground clearance from concrete?

[ScottR]

Not much prior DIY experience here but wanted to build my own shed on top of concrete. However, because of heavy rains, concrete could get wet inside shed and I keep some boxes there that may get wet. (Melbourne weather)

I'm looking for a structure that I could put underneath the shed over the concrete and checked Decko tiles (or any deck tiles). The tiles has a height of 20mm, is 20mm height clearance enough for the boxes I have inside the shed not to get wet? Is it too low? Any alternatives for this?

Image below is what I was thinking of doing where the grey colour around is concrete. Any advice? thanks!

[EricL]

Hello @ScottR 

Thanks for sharing your question about your sheds ground clearance. There have been quite a few discussions about sealing the inside of the shed to prevent water from coming in. This often involves using a silicone sealant to prevent water from coming under the shed wall. 

You could then use your tiles inside the shed to add additional protection for your boxes. For secure protection of precious items and paperwork, I suggest storing them in Ezy Storage Waterproof Box rather than cardboard box. So even if you get trapped moisture inside the shed it will not affect your stored items. 

However, if you place the shed over the Deko tiles, water will pass through gaps and make the inside of the shed damp. 

Here are the links to the previous discussions about sealing a shed:

• How to seal the bottom of shed walls? by @jjebw

• How to seal the bottom of the shed? by @MattR85

• How to waterproof existing garden shed? by @basilmabraham

• How to water-seal edges of an Absco garden shed? by @bennyboy

If you have any other questions we can help with, please let us know.

Eric

[ScottR]

Thanks for the response @EricL ! 

It sounds like having decko tiles underneathe the shed is not recommended. I haven't started on the project yet but will look into just putting the shed over flat concrete at the back of the fence. 

As suggested, I can just seal the surrounding areas of the shed using Sikaflex  I can use this inside the shed around the perimeter as I won't have access to the back of the shed and to the left side of it. I plan to place it at the edge of the property with fences surrounding it. No vegetations on both ends of my property.

Hopefully that should take care of the water seeping inside. Would 1 roll of 300mL be enough sealant to cover for a 3x3m (10m2) shed?

[EricL]

Hi @ScottR 

It's best to get two rolls just in case you run short. It's a better alternative to stopping in the middle of the job and having to run to the store. But if you manage to cover the area with just one roll, you can return the unopened roll back to the store on your next visit.

If you need further assistance, please let me know.

Eric

[MitchellMc]

Hi @ScottR,

I thought I'd point you to a couple of articles that you might find handy: How to waterproof a shed floor and How to install a shed floor.

Since making these adjustments, my shed floor has been completely moisture-free for the first time in decades.

Please let me know if you need any questions.

Mitchell

[ScottR]

Hi @EricL  & @MitchellMc

Thanks for the tips! Also appreciate the videos and articles you have sent me. I specially liked the "How to install a shed floor" better than just applying sealants. I haven't started this yet and will start from a very clean slate.  Waterproofing a shed floor may not be feasible for me because I potentially may not have access to two sides of the shed since I'll put the shed way at the corner near the fences. Thanks! 

[Jason]

Great. Let us know if you need any further assistance @ScottR, and please also provide updates as the project progresses. It's a common problem so I'm sure there will be many other community members keen to see your success.

Jason