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Suggestions for small shed foundation?

mikebarker
Having an Impact

Suggestions for small shed foundation?

Hello all! I am planning to build a small wooden storage shed as a project to gain some carpentry skills. It will be approx 3.5m wide x 2.5m long (Staying under the limits of permit requirements where I am in Victoria). I am on a sloping block and have had a small area cut into the slope, and one side built up to level it by an excavator (See attached images).

 

Essentially, the built-up side is quite soft so I don't think I should use the concrete foundation blocks that are often recommended.

 

I've been looking into multiple options, I was initially sold on a gravel pad (This article was very persuasive and helpful and this video too) but I'm now also exploring options for some footing, similar to what you would use for a deck but there are so many options I'd love the community to offer some ideas based on the area I have.

 

I was planning to dig some holes and use those cardboard footing tubes and pour concrete in and then use some kind of bracket to attach some lengths of 90x90 treated pine as the basis on which to build the shed floor joists.

 

I am open to pouring a concrete pad but I'm not a huge fan of the permanence of it (or the cost!) but I'm not against it if it's the best solution.

 

I also think I should retain the left side where it has been cut into. It's not very high approx 300mm, a single sleeper would probably do it. Suggestions on a simple approach to this would be welcomed. I expect if I go the gravel pad route then this would just be one of the sides of the container for the gravel.

 

So, to summarise:

 

1. Which solution would be favourable for this size, area and ground, factoring in cost/simplicity? Gravel pad, footings (and what kind) or a concrete pad?

2. What approach should I use to retain the side that has been cut into?

 

Thank you all so much!

 

 

Front view, area to be potentially retained on the leftFront view, area to be potentially retained on the left

Side viewSide view

 

Re: Suggestions for small shed foundation?

I think 200 x 50mm sleepers should be adequate, @mikebarker. You're not retaining a whole heap of weight, just using them to stabilise the slope.

Post-wise, you can cut up some H4-treated posts and concrete them into the ground or use H4-treated premium posts. For the back and right-hand side, I'd recommend 800mm posts with 600mm of them in the ground in a decent-sized concrete footer. That's not really going to be less effort than the steel posts but it could be more budget-friendly.

 

Mitchell

 

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Re: Suggestions for small shed foundation?

Thanks for the sleeper info.

 

Instead of concreting, can I use a post of some kind just driven into the ground? Like a sleeper peg? Or is this not an appropriate use of those?

 

If I do need to dig holes down, do I need a post-hole digger ideally?

MitchellMc
Bunnings Team Member
Bunnings Team Member

Re: Suggestions for small shed foundation?

Those pegs are designed to pin a sleeper in place; they will not stop one from being pushed over if you're compacting behind it on a slope @mikebarker.

 

A manual post-hole digger will do the job if the soil isn't too rocky. We also hire them, which will make the job a whole lot easier.

 

Mitchell

 

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Re: Suggestions for small shed foundation?

Noted, thanks so much @MitchellMc

Re: Suggestions for small shed foundation?

Finally getting this project underway! @MitchellMc do I need a 200mm post hole digger like you recommended? If the posts are to be ~90mm wouldn't a 150mm post-hole digger or smaller be adequate? I'm quite limited for space on the back side so just curious. Also, can you advise on how to ensure the posts are level on both axes to where I need them for the sleepers? Do I need to put temporary supports in place while the concrete sets?

EricL
Bunnings Team Member
Bunnings Team Member

Re: Suggestions for small shed foundation?

Hi @mikebarker 

 

It's good to hear your about to start your project. I recommend giving your local store a call first to make sure you reserve your post hole digger before the weekend. You'll also be able to ask what size is available at the store. My number one tip is to make sure that the locking pin for the auger is attached to the machine and that the auger tip is still sharp.

 

Technically it would be better to have a larger hole to hold the post in place. This will prevent the concrete footing from leaning or twisting should any weight be applied to it.

 

To ensure the level of the footing it will be necessary to put temporary supports while the concrete cures. I also suggest using a builder's line to makes sure that the posts are lined up and a spirit level so that the posts are straight.

 

If you need more advice or information, please let us know.

 

Eric

 

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Re: Suggestions for small shed foundation?

@MitchellMc If I were to use steel posts I assume the post setup would be the same i.e. use jointer posts on the middle parts? (Top left and right sides). If I did that what would you suggest for the back left post/s? Do you think I could get away with a single corner piece given the differences in depth? 

Re: Suggestions for small shed foundation?

A single corner piece would be fine with the steel posts system @mikebarker. For the left side, use a longer post to accommodate the sleepers' height difference.

 

Mitchell

 

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Re: Suggestions for small shed foundation?

I started digging my post holes (They only had a 150mm diameter manual post hole digger at Bunnings so I've been using that, is that adequate or should I seek an alternative? I don'r really have anyone on hand to use a 2 person petrol unit). I managed to get nearly 600mm on the left side, it was a real struggle, as the clay is like rock. I had a massive crow bar on hand which helped but, on the top right side, the side that is mostly built up/filled in I have hit rock/a density of clay I cannot get past. I reckon I'm about 500mm deep, including the topsoil.

 

I will use these Jack Retain-It 750mm x 50mm retaining wall posts. They suggest you only need 350mm in the ground for 2 sleepers, with 400mm out of the ground (Which I will use on the right side at least, the left side is about 300mm high so not sure if I should use 1 or 2 sleepers). This would solve my issue of not being able to dig any deeper but @MitchellMc you mentioned being 600mm into the ground for posts so do you think I'll be ok?

 

Recommendation for Retain-it post depth attachedretain it post depth recommdendation.png

 

 

Re: Suggestions for small shed foundation?

If it's solid ground, I'd go with the recommendation from Jack, @mikebarker. The 600mm was just a depth that would ensure a solid post, not the bare minimum you could do. I tend to over-engineer my suggestions to err on the side of caution.

 

Mitchell

 

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