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How to prepare base for new garden shed?

I’m encouraged by the helpful posts. I have just laid a a 3m x 2.5m concrete base 90mm thick. A garden shed will be erected soon. There was no gravel base installed. It’s beside the neighbours fence where it appears minimal water emerges. Unfortunately there is no space for an agi pipe between fence and the shed. What would be best to prepare the base to prevent cracking?

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JacobZ

Hi @philbyone,

Welcome to the Bunnings Workshop community, it is wonderful to have you with us.

Do you have some photos of the concrete slab that you could show us?

If you need a hand uploading images, let me know. I am happy to help if required.

As the slab has already been poured, there's not a huge amount we can do at this point. Keeping water away so that the ground beneath doesn't erode and the slab doesn't move is about all you can do.

You've mentioned there is no space for drainage between the fence and the shed, but is there space on the sides and front of the slab?

Any drainage you can add will likely be helpful. Check out How to install garden drainage for some guidance on the installation process.

Let me know what you think.

Jacob

philbyone

Jacob. Hope photos come to you! I’m happy to do some drainage but hoping by sealing the slab on top and the edges will prevent water damaged. What do you think?

JacobZ

Hi @philbyone,

Sealing the slab will prevent water from soaking in and seeping through it. If you wanted to seal it, you can use a product like this Bastion 15L Matte Concrete Sealer, but it won't protect you from water getting under the slab from the sides.

Looking at the photos, I'd say you've got enough room to install a basic drain around the perimeter of the slab, including at the back along the fence line. It doesn't need to be much, just enough to catch the water and divert it around the slab.

Check out How to install garden drainage for some guidance.

Jacob

philbyone

Thanks Jacob

On the other side of the fence the neighbours have a concrete slab already down. Also the fence posts are concreted in, the cement protrudes out onto my land and make it near impossible to put down agi between the fence and my proposed shed. I don't want to break up the concrete which embeds the fence post obviously. Their slab is 600mm higher than my slab. I notice there already exists some rotting on the bottom board of the fence, it looks like water is running off their slab. I'll investigate laying some 65mm agi pipe. I wonder if I could put a bit of spouting on the back of my shed to catch some run off!.

Ill certainly secure and paint on that Bastion concrete sealer. Thanks.

Phil

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