I'm planning to make a timber frame and flooring for a 3 x 2.3m (10 x 8ft) prefabricated garden shed. The construction method I had in mind is similar to the following image from Flickr:

Dog Run - Doggie Deck Foundation and Frame

For the floor I was planning to use 190 x 35mm (approx 7 x 1.5") H3 treated pine but something I'm not sure of is whether I should leave a small gap between each piece of timber to allow for expansion because of moisture / temperature? Below freezing temperatures are extremely rare here the normal temperature range is about 5 - 38C (40 - 100F).

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    Keep i mind that the entire shed, along with the contents of shelving, etc., will be carried by the cantilever in your floor framing. I'd move your footing blocks outboard where possible.
    – isherwood
    Commented Nov 11, 2017 at 16:48
  • White wood framing and treated sheathing? Hmmm...
    – isherwood
    Commented Nov 11, 2017 at 16:50
  • Why not use extra blocking (2x8?) to occupy all the slots in the concrete piers? Why planks for the flooring? Isn't plywood what is used nowadays? All the gaps in the planks will allow bugs in. Plywood is impenetrable and really strong.There should be blocking under the seams of the plywood. Commented Nov 12, 2017 at 21:38
  • @Jim thanks for the tip - I was thinking plywood wasn't suitable for potentially damp areas but I see now that many types are. I'll also consider some extra blocking, that was just the closest photo I could find to what I had in mind but it sounds like a good idea to add more.
    – PeterJ
    Commented Nov 13, 2017 at 5:41

1 Answer 1


There is no need to leave a expansion joint cause treated lumber has a tendency to shrink when it gets warm due to the moisture leaving the lumber. In my experience nail everything tight cause when it does shrink you will have perfect joints.

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