Shed floor joist spacing?

Is it going on a concrete base? Joists are generally spaced 12" 16" or 24" depending on timber size, span and what the floor is being supported by

 

Definitely be looking a 18mm for the flooring, instead of 11mm OSB, your need joist would need pretty close spacing with 11mm.

 

As above re:11mm, would use that on a roof let alone a floor, 18mm minimum @ 400mm centers.

 

16" for walls u cud prob go 24" if you are putting up plywood, why dont you just do a concrete base itll be cheaper than a timber floor

 

I would say so, certainly if you can do it yourself.

I believe getting the concrete delivered should be about £250-£300 depending on were u are

Either way defo go for 18mm ply, its not much more expensive and its alot stronger

 

There are many factors here to consider.

Regardless of joist spacing, there is significant opportunity for movement where the ground hogs or heaves at the joist where boards meet. This is a weak point. The way to overcome this is to double board the floor over lapping the boards by 50% wherever possible.

The ground conditions will help determine whether a concrete base will be better in the long term. Is the ground wet? Ex flower bed? low point in the garden? near trees or roots?

Pointless exercise if the floor joists will rot in a couple of years.

My preferred option for sheds - may be out of OP budget:

Concrete sub-base. 75-100mm treated timber battens, DPC over the battens, 2no 18mm marine-grade ply cross lapped (much stronger than 1no 25mm)

I then use a roll of EML mesh screwed with washers along the ends of the timbers to ensure good ventilation to underneath without allowing vermin or leaves.

The plywood or Shiplap cladding should come down vertically a touch over where the concrete finishes. This will ensure that minimal rain gets onto the concrete, and certainly any water running down the cladding. (The concrete sub base slightly smaller than footprint of shed if that makes more sense).

 

i am around 18 stone i helped my neigbour erect his 5x8ft shed a few weeks ago and his shed floor nearly collapsed under my weight
luckily i was ordering timber the next day and had ordered another sheet off 11mm to place on top

 

Utter bull excrement, totally over the top.

 

No wooden sheets under 18mm are structural.

 

No denying over the top, but they last 30 years or more and there is no issue with damp or vermin. Or falling through.

 

Marine ply is for constant immersion in sea water not a shed base.

 

If you have had this information on good authority,why are you here asking people there advice, obviously you can't trust it that much. Everyone is telling you 18 mm is the minimum thickness ply for a floor for a reason, and a minimum of 400 mm centres for joists. Either do it right and pay a bit extra, or do it cheaply as your mate dave or bob has told you and watch it fail then cost you again to put it right.

 

So that's why they sell it in every builders merchants in every urban in-land area. Because it's only for 'constant immersion in sea water'

 

Are you confusing marine with wpb? very different.

 

Not every builders merchant stocks marine grade ply as standard, it's normally special order as it's twice the price of WBP ply.

 

Marine ply performs longer in both humid and wet conditions and resists delaminating and fungal attack. Its construction is such that it can be used in environments where it is exposed to moisture for long periods such as under a shed.

The walls of a shed however, if they are WBP battened and clad with shiplap will not be exposed to moisture for long periods.

I agree it may be over the top as I introduce the ventilation as well, which should keep WBP going for a while as-well.

 

My post reads sell not stock.