Shed base (for wooden posts) (Ed.)

[pemba]

Hi guys sorry for starting yet another thread on shed bases but I guess we all have our own problems to overcome.
I’m erecting a 10’x8’ shed in between 2 large trees at the bottom of the garden. This has always been a “dead” area due to the tree shading and roots. To overcome the root problem I’m planning on having a raised frame made of 4”x4” fence posts sitting on top of a couple of inches of MOT. Corner joints will be standard builders 90 degree galvanised jobs with coach screws. Where the roots are near the surface I will ensure there is some free space for them to grow and fill (they have never come above the soil before so I don’t anticipate this happening). I intend backfilling the frame with MOT and compacting it with a plate wacka. So here come the questions:
1) does it sound reasonable?
2) do I need to strengthen the frame if compacting? Thinking of another fence post midway on 10’ leg?
3) should I cover the fence posts (frame) with vizqueen to stop moisture?
Far too many things to consider

Many thanks for reading and apologies it’s so long.

 

[JohnD]

If you bury the ends of the posts, or any part of the frame, in the ground or the MOT, they will rot. You can avoid this by casting a concrete block into the ground, projecting by six inches or so with a galvanised socket bolted or cast in to it.

Place them inside the cladding and below the roof to keep rain off. Paint the steel before fitting to prevent rust.

I don't know why you want corner brackets because you can bolt the horizontals of the frame to the posts. Studding is cheaper.

You can staple membrane to the frame before fixing the cladding, it will keep rain, draughts and some insects out.

 

[bernardgreen]

45 years ago we built this timber framed house. The 22 posts stood on paving slabs, Between the post and the slab is a piece of lead sheet which seals the end grain of the timber to prevent moisture affecting the timber. Still in good condition,

 

[Deluks]

Compacting the ground could cause problems for the tree roots.

You might be better off raising the shed off the ground by a few inches, your posts can just sit on a concrete block, or 50mm paving slab.
Use as many as you need, 9 will probably be enough, and then build a framework as if you were building a deck. Put the shed on this frame.

You could use 'bolt down' fence post sockets (ie: metpost) on the bottom of each post, to protect from water and spread the load on the concrete.
Weed membrane underneath, chicken wire around the edges to deter rats and digging from foxes.

 

[mrrusty]

Use easypads https://easypads.co.uk/ They can either sit on very shallow dig-outs or be buried right up to the top. Once installed, dead easy to level up, fit a timber frame and build on top.

 

[JohnD]

What are they made of?

 

[Notch7]

Or foundation screws

https://www.amazon.co.uk/Galvanised-Holder-Support-Square-Bracket/dp/B085HMVRDG/ref=asc_df_B085HMVRDG/?tag=googshopuk-21&linkCode=df0&hvadid=588076632935&hvpos=&hvnetw=g&hvrand=2757764360771359753&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9045149&hvtargid=pla-1658778561507&psc=1&mcid=f8c1b290b80d3d3d90ea44f019536bc1

 

[pemba]

Many thanks for the considered responses guys.

TBH I had thought that wrapping the posts in Vizqueen would stop/delay the rotting process but it appears that the community does not share that view. Perhaps doing this would actually lock more moisture in thereby doing more harm than good.

I like the ideas proposed and will probably go with the slabs supporting a decking type framework.

Many thanks again guys.

 

[mrrusty]

What are they made of?

Concrete with a tube down the middle supporting a screw jack with top plate. For an 8 x10 you'd only need 1.5T ones. I used them recently for a 6.5m x 3.5m SIP garden room. https://community.screwfix.com/threads/garden-room.256842/