Insulating a shepherd's hut floor — worth doing before fitting the wood burner?

Absolutely do the floor before anything else goes in — you'll kick yourself if you don't. Once that burner is sitting there with its hearth pad down, you're not moving it again in a hurry.

On my tiny house build I used 50mm Kingspan TR26 between the joists, then a layer of 6mm ply on top before the tongue-and-groove flooring. The difference it made was immediately obvious — cold coming up through an uninsulated floor is brutal in winter, and a wood burner can't really compensate for that kind of heat loss, it just ends up working harder.

For a shepherd's hut specifically, bear in mind the steel chassis underneath means you've got a real thermal bridge situation. Some people add a layer of foil-faced bubble wrap beneath the joists as a radiant barrier too — not a substitute for proper insulation but it does help with that chassis issue.

A few things worth thinking about:

• Vapour control layer — shepherd's huts can get condensation issues from underneath
• Joist depth — how much room have you actually got to play with?
• Weight — PIR foam is your friend here vs mineral wool if you're worried about the chassis rating

Has anyone used spray foam on a shepherd's hut floor? I've seen it mentioned a few times but always been a bit wary of it making future repairs a nightmare.

Would love to hear what others have done — especially if you're living aboard full-time through winter rather than just weekend use. The cold tolerance calculation changes a lot!

@WattVicky is 100% right — fitting floor insulation after a wood burner is like remembering to put your socks on after your shoes. Technically possible, deeply regrettable.

I learned this the hard way in my own setup. Spent a weekend on my back with a stanley knife and some 50mm Celotex trying to squeeze

Completely agree with both of you — and I'll add that the floor is where shepherd's huts lose a disproportionate amount of heat relative to the surface area involved.

On mine I went with 100mm Celotex between the chassis members, foil-faced side up, taped at every joint with proper vapour-barrier tape. The difference before and after was immediately noticeable — that cold radiant chill off the floor in the morning completely gone.

Worth noting: if your chassis is steel (most are), those members act as thermal bridges regardless of how well you fill the bays. A thin layer of 12–15mm PIR across the top of everything before your deck boards goes down addresses that properly. Adds almost nothing in floor height but makes a meaningful difference.

Do it now. Every other job can be undone. That one can't.

Practical point to add: the floor void in a shepherd's hut is typically quite shallow, so you're usually looking at rigid PIR board rather than mineral wool — Kingspan or Recticel cut tight between the joists, taped at edges.

Worth also considering a vapour control layer on the warm side before your floor deck goes down. Huts on metal-wheeled chassis get significant cold bridge through the frame, and without it you can end up with interstitial condensation that rots the substrate from underneath — damage you won't notice until it's serious.

If you're also planning any 12V/240V cable runs under the floor (heating controller, socket feeds to the garden office end), route conduit now before the deck goes on. I had to drill back through a finished floor to sort a cable run and it's not a job I'd repeat.

Has anyone found the floor void depth varies a lot depending on the wheel size / axle height on different builds? Mine is a garden office conversion and I'm genuinely unsure whether I've got enough clearance for decent rigid foam plus a vapour barrier without losing too much floor height inside.

Also — is there a meaningful difference between going with something like Celotex vs Kingspan for this kind of application? I keep seeing both recommended but struggling to find a clear comparison for a damp-prone underfloor environment specifically.

@CarlBaker when you say the void is typically shallow, did you find a minimum thickness that still made a noticeable difference, or is it a case of just fit as much as you can get in?