Converted an old shepherd's hut last summer — worth insulating the floor first?

Done a few conversions over the years — narrowboat, two vans, and a static — and floor insulation is honestly the one thing I'd tell every first-timer to prioritise before anything else goes in.

On the static especially, I deeply regret not lifting the floor panels before I fitted the electrical runs. Had to redo a proper chunk of it when the cold bridging underneath was causing condensation issues that were getting near the battery bank. Nightmare.

For a shepherd's hut specifically, you've got a few things working against you:

• Metal or wooden chassis = cold bridge city in winter
• Small footprint = ground chill affects the whole space proportionally more than a bigger structure
• Typically raised on wheels = airflow underneath is constant, which is great for damp but brutal for heat loss

I'd go with at least 75mm rigid PIR board (Celotex or Kingspan) between the joists, foil-faced, taped at every joint with proper foil tape. Don't bodge it with loft roll — it'll absorb moisture and collapse over time if there's any ground damp rising.

If you're planning any underfloor heating or even just a wood burner, you'll thank yourself enormously. The payback in comfort and reduced heating demand is significant, especially if you're running off solar and trying to keep the Victron system from working overtime through autumn.

What's the floor construction like on yours — timber frame joists or a steel deck? That'll change the approach a bit. Also curious whether you're planning to use it year-round or just seasonal, as that shifts the priority level considerably.

@GafferTapeKing19 couldn't agree more — learned this the hard way with my own hut conversion. I'd already run all the 12V cabling, mounted the Victron MPPT, even fitted the little wood burner before I properly addressed what was beneath my feet. First winter, the cold just crept up through the chassis no matter how hard that burner worked.

Went back and retrofitted 100mm rigid PIR between the floor joists and it was genuinely transformative — like the whole space finally made sense thermally. The burner went from working overtime to barely ticking over.

The lesson I'd pass on specifically for shepherd's huts: those traditional curved roofs lose less heat than you'd expect, but the metal chassis conducts cold ruthlessly. Floor first, every single time.

Really valuable thread this. @GafferTapeKing19 is spot on, and poor @SteveBurns99 will know better than most how painful retrofitting floor insulation is once everything's already fitted out!

One thing I'd add specifically for shepherd's huts — those traditional chassis rails can create real thermal bridges if you're not careful around the perimeter. Worth thinking about how your floor insulation ties in with whatever you're doing at the wall base. I used 100mm rigid PIR in mine and the difference was immediately noticeable, but I nearly bodged the edge detailing completely.

Also worth checking moisture — huts often sit quite low to the ground and damp can wick up through older timber floors before you've even started. A decent DPM underneath your insulation layer saves a world of grief later on.

Great thread, and sympathies to @SteveBurns99 — sounds like you're mid-grimace even typing that out!

One thing I'd add from my shepherd's hut build: the type of insulation matters as much as the timing. I initially went with rigid PIR boards which are brilliant thermally, but shepherd's huts flex quite a bit on the move (ours gets towed occasionally), and I ended up with a couple of hairline gaps along the edges after the first winter. Second attempt I used a combination — rigid layer topped with a thin acoustic/thermal roll to account for that movement. Sorted it completely.

Also worth checking your wheel arch clearances before committing to thickness — I lost about 20mm headroom unnecessarily because I hadn't planned that properly. Small thing, but in a hut that's genuinely noticeable!

Great thread! @GafferTapeKing19 makes a solid point, and poor @SteveBurns99 clearly has the battle scars to prove it.

One thing worth flagging specifically with shepherd's huts — those traditional iron wheels and chassis act as absolutely brilliant cold bridges if you're not careful. Even with decent floor insulation between the joists, heat can leach out through any metalwork that's in contact with your floor structure. Worth either thermally breaking that connection or at minimum adding a decent layer of rigid PIR board across the whole floor deck before your ply goes down, rather than just batts between joists. Made a noticeable difference in mine. Also don't forget the gap underneath — if it's exposed to wind that air movement will undermine even good insulation. A simple skirting arrangement around the base during winter months helps enormously.

@SteveBurns99 's floor situation is giving me flashbacks to when I skipped it in my first shepherd's hut and spent three winters essentially sleeping on a very rustic fridge.