Best shed floor material?

[dontpanic]

Hi, someone wants to build me a 12'X8' durable & secure shed but he is insisting on a chipboard floor and roof.

The shed will be constructed as follows:

8X2 tanalised joists on concrete blocks,
floor on top of joists,
4X2 studwork frame on top of floor,
4X2 rafters, etc,
sides made of 18mm WBP plywood nailed onto frame from outside.
shiplap cladding nailed to that.
big strong 44mm wooden door.

So, I'm prejudiced against chipboard. I don't care if it's P5 or 'moisture resistant' - it's still weetabix. Am I wrong?

Is there a good alternative material for the floor?

The builder says plywood or t&g floorboards are unsuitable and will distort or decay and split.

Any advice from those with experience of bespoke sheds would be appreciated.

[Bob225]

wpb or Stirling board, chip or osb will rot or fall apart tbh

[big-all]

has the price been set yet ??
sound like he is talking up the cheaper quicker to fit materials

[arco_iris]

Hi, someone wants to build me a 12'X8' durable & secure shed
...

Is there a good alternative material for the floor?
...

Any advice from those with experience of bespoke sheds would be appreciated.

PHENOLIC PLYWOOD.

(As used in back of trucks, and horseboxes).

[dontpanic]

has the price been set yet ??
sound like he is talking up the cheaper quicker to fit materials

No, I am paying for the materials direct from the merchant as he specifies and paying separately for labour.
He's a friend and wants to do a good job. Fitting T&G chipboard flooring is likely easier as it slots together.
He says it will perform better as it does not suffer expansion/contraction/warping with variation in weather and that moisture resistant versions are perfect for exterior use in a shed.

I don't trust chipboard for a potentially damp environment but how does moisture resistant chipboard fare up? I mean, if it is moisture resistant why have I never heard of it being tiled onto in a bathroom for example?

By phenolic plywood, is that the same as WBP / phenol formaldehyde resin ply?

[jaeger]

wpb or Stirling board, chip or osb will rot or fall apart tbh

I thought sterling board was OSB?

[dontpanic]

Hi, someone wants to build me a 12'X8' durable & secure shed
...

Is there a good alternative material for the floor?
...

Any advice from those with experience of bespoke sheds would be appreciated.

PHENOLIC PLYWOOD.

(As used in back of trucks, and horseboxes).

I looked it up, it has a plastic surface on both sides. That looks like it would absorb less moisture from underneath or from walking on with wet boots, etc but if it does get damp, wouldn't it take longer to dry out? I was thinking that WBP plywood would breathe so that any mosture from outside would evaporate through the top of the floor being un-sealed?

This phenolic ply is not much more money than WBP so it looks like a good choice. I don't mind spending more on materials if they will last. At the moment the cost is about £600 so I don't mind another £100-£200 if needed.

[Job and Knock]

Another vote for phenolic plywood. Often sold as re-useable shuttering material, but not cheap. Make sure that you seal the edges after it's cut to size, but before it's installed

[arco_iris]

Why would it get damp? It is used in the back of articulated trailers, lorries & horseboxes, and lasts for years. You asked for recommendations.....

[Job and Knock]

I looked it up, it has a plastic surface on both sides. That looks like it would absorb less moisture from underneath or from walking on with wet boots, etc but if it does get damp, wouldn't it take longer to dry out? I was thinking that WBP plywood would breathe so that any mosture from outside would evaporate through the top of the floor being un-sealed?

It has phenolic resin coatings on both faces so it cannot absorb moisture at all if you seal the edges before fixing it in place. Drying it off is either a case of mopping it out, or just letting the water evaporate as the plywood won't absorb it. That's how it's designed to work in a concrete form. Continual absorption of water followed by drying out on unsealed plywood can eventually cause delamination, which is why construction plywiid is very rarely seen on the outside faces of buildings - it's almost always underneath either a membrane or some other impervious cladding such as zinc sheet, Corian panels or lead.

The only thing I know which will outlast it is MDPE or HDPE - and the price of those is astronomical (£200 to £350 plus VAT for a 2500 x 1500 x 18 sheet)

[big-all]

14 years ago i built my 12x10ft shed 3x2 for joists and studs at 2ft centers
18mm ply floor and roof
12mm ply on inside walls and 15mm txg shiplap on the outside
2 coats ducks back every 3 or so years good as new no decay no rot
i personally would avoid chipboard but thats just me osb/sterling board for the roof may be fine but the floor gets loads off wear
my mate chose osb for his fancy shed floor comming up 2 years ago not sure how well its doing

[jaeger]

How about recycled plastic board, just a thought. I've never used it or know anyone who has
But it comes in 8x4 19mm sheets.

https://tinyurl.com/y9qjmegn

[Job and Knock]

I've used similar stuff for site hoarding a couple of times. It is a recycled relative of the MDPE sheet I mentioned above, but made by compressing chipped poly bottles (in the main). It also has voids in it so a bit lighter than solid plastic sheet. I think you'll need to ensure that it is adequately supported (say 300mm centres or a sheet of something beneath it) because in warm weather it can droop between the supports if they are too far apart. Other than that the only thing I'd say is that it can be really slippery to walk on if/when it's soaking wet

[Bob225]

Green chip is moisture resistant (just the adhesive), exposure to moisture outdoors will see it break down

If your buying wbp anyway another 10 sheets or so should drop the price from a proper timber yard

Stirling board iirc is OSB 3 what is moisture resistant and made from smaller strands than OSB

[ahfix]

sides made of 18mm WBP plywood nailed onto frame from outside.
shiplap cladding nailed to that.

I'm no expert but I can't see the justification in having 18mm ply sheath for a shed. My current shed is 15mm weatherboard (tongue and groove) which is strong enough.

If you are keen on the ply sheathing I'd go down to 12mm but make sure you also have a breather membrane between it and the shiplap.

My shed has 18mm pine tongue and groove floor boards approx 100mm wide. Which will be miles better than chipboard. I would treat the pine boards with a suitable finish.

ah