Converted an old shepherd's hut last summer — still can't crack the damp issue

Damp in shepherd's huts is a beast — been there with my motorhome conversion and the principles are frustratingly similar. The problem is almost never one thing, which is why it defeats people for months.

My money's on a stack effect combined with thermal bridging at the chassis rails. Those steel underframes are absolute cold bridges, and if your floor insulation isn't completely breaking that contact, you're basically running a condensation factory from the bottom up. No amount of ventilation fixes that root cause.

Few questions worth thinking through:

• Is the damp appearing in specific spots or general throughout?
• What insulation did you use, and how thick?
• Do you have any electric heating running overnight, or does the space go completely cold?

The overnight cold drop is often the killer. I run a small Victron-powered setup in my rig that keeps a base temperature going — even just 5°C stops most of the surface condensation forming.

The other thing worth investigating — and I say this as someone who spent three months blaming their ventilation before finding it — is whether moisture is wicking up through the floor structure itself. Shepherd's huts sitting on uneven ground can trap standing water under the boards seasonally.

Would love to hear what materials you used for the walls and roof build-up. There's a real split in opinion on here about vapour barriers in that kind of structure — some swear by them, others think they create more problems than they solve.

What does the damp actually look like? Condensation trails, tide marks, or just a general muggy feeling? That changes the diagnosis completely.

@LiFePO4Nerd — have you actually logged the dew point inside vs the wall surface temps? I stuck a cheap SHT31 sensor on my garden office wall cavity last winter and the data was genuinely eye-opening. Turns out my "ventilation problem" was actually a thermal bridging problem at the steel frame joins — no amount of airflow was going to fix that.

With shepherd's huts specifically, are those wheels creating cold spots where the chassis meets the floor structure? I'd suspect that junction before anywhere else. Effectively a giant thermal bridge running the entire perimeter.

What insulation did you go with? Rigid PIR or batts? And is there a proper VCL on the warm side, or did it get... approximated during the build? That last bit seems to defeat half the DIY conversions I've read about.

@VoltPaddy that's a really useful approach — do you just wire the SHT31 directly to a Pi or are you using something like an ESP32 to push readings to Home Assistant? Wondering how much faff the setup actually is for a non-coder.

My garden office had persistent cold-spot condensation last winter and I never properly diagnosed where the dew point was being hit — just threw a dehumidifier at it and hoped for the best. Not ideal.

@LiFePO4Nerd — curious whether you've checked if the hut's steel chassis is acting as a thermal bridge? I'd imagine that's a nightmare in a shepherd's hut specifically, given how the frame connects floor to exterior.

@VoltPaddy @CliffWill — I ran a similar sensor array in my van conversion using SHT31s fed into an ESP32 rather than a Pi, which cuts the power draw significantly if you're running off a small LiFePO4 bank. The ESP32 logs to InfluxDB via WiFi and I can pull Grafana dashboards remotely.

The bit people miss is where you mount the sensors. Surface temperature on the inner wall skin tells you almost nothing useful on its own — you need to capture the temperature at the cold bridge points specifically, typically the frame junctions and floor perimeter on a shepherd's hut. That's where condensation nucleates first.

On my setup I use Victron's temperature sense leads alongside the SHT31s to correlate with battery bank behaviour overnight, which helpfully timestamps the coldest ambient periods automatically.

@PaulaFisher91 — the ESP32 route is dead handy for this sort of thing, especially if you're wanting to run it battery-powered without a Pi sat there drawing current all day.

One thing worth adding to the sensor discussion though: don't just monitor one spot. Damp in a shepherd's hut tends to concentrate where you least expect it — around the chassis rail junctions, under the floor boards near the axle mounts, and behind any wool/sheep fleece insulation if it wasn't properly vapour-managed during the fit-out. I'd place sensors in at least three locations before drawing any conclusions.

Also @LiFePO4Nerd is right that it's rarely one cause. In my experience with timber structures, cold bridging through the steel frame is massively underestimated. Insulating that before anything else often makes a dramatic difference to surface temps.