3x3 shed floor layout

[Alexnh]

I'm replacing a rotten shed floor. The 3x3m shed was built on the floor, so I jacked up the walls removed the rotten edge 38x38mm bearers and OSB, laid 38x70mm treated timber on blocks with DPC in between, and lowered the walls down again. The whole shed is built on a concrete slab.

My intention is lay a new floor of 15 or 18mm plywood inside the walls this time, with the edges resting on the edges of the new bearers, and to lay more 38mm bearers on more blocks to support it.

How would you sheet the floor and how many bearers do I need? Two full sheets then lay remainder with cut down pieces? Or, run a main bearer down the centre of the shed with sheets finishing in the middle? Bearers every 500mm?

Any smarter way to do it that'll let me cover it without needing a 4th sheet of ply?

 

[sircerebus666]

Did you not make a note of how the existing floor was laid and replaced like for like?

 

[Alexnh]

No sir, I am not replacing like for like for a number of reasons, some of which I've outlined already - it didn't look like a particularly good job so why would I replicate it?
Since I have a blank canvas what I would like to know is how to fit the floor well, with the appropriate materials and do so efficiently. Can you help with that?

I think the original builder used the same 11mm OSB 2 boards for floor and roof. These boards and the bearers certainly weren't sufficient to be laid directly on the slab, although one might argue nothing would have been since it would get so wet. I only had time to complete stage 1 this weekend, raising the exterior and replacing the rotten edge floor bearers which the walls sat on. Next weekend I'll replace the floor boards. From what I've seen so far the OSB boards only had support at 1m centres and the boards only seem to have been 1m wide.

I think I'll use 38mm treated timber for the joists and bearers. I'll lay one sheet of board across the width, then an off cut, then the same again, staggered for the second board in, and then fill the final bit at the back with the bits I have left. I've got a couple of small bits of ply from other projects.

So my main question now is what ply to use, thinking EN636 & 314 class 2 (humid) or possibly class 3 (external) if I can find it at a reasonable price?

 

[scbk]

It's not the answer you're looking for, but when I rebuilt a shed floor I used 150mm wide boards/planks, then once the walls were fixed to that laid 9mm osb over the top to cover the gaps

 

[Alexnh]

That's an interesting way of doing it. What was the span and did you have any supports or did the boards span the full width? Must work out fairly expensive compared to a sheet and joist?

 

[scbk]

The framework underneath is 3x2's, all round the side then spaced approx. 500mm as joists. The shed is about a 12x8, the floor boards run lengthways. Probably cost about £50 for all the timber then £30 for 3 sheets of osb.

Defiantly over engineered but the floor is rock solid and will hopefully last a lifetime (it was treated with creosote)

 

[Alexnh]

Yeah, my joists are much smaller so I'm making up for it with thicker plywood which is the most expensive bit. I might yet use larger timbers as joists or at least put the 38x63 or 75mm pieces upright.

 

[foxhole]

I used pallets , free and long lasting, with shed overhanging get very little wet.