Shelter and body heat
Get off the ground, out of the wind, and dry.
Everything for this step
- Field guide
- Rope, knots and lashings → 5 sections Stone and earth building → 18 sections
- Builds
- None yet.
- Reference sheets
- 1 sheet in Rope, knots and lashings · 10 sheets in Stone and earth building
- Sciences it rests on
- Physics · Engineering
- Track
- Emergency and temporary shelter, level 1 of 1
Why this matters
Hypothermia kills in hours, not days, and it kills at surprisingly mild temperatures once you are wet and moving air is stripping heat off you. The ground steals more heat than the air does.
The shape of it
- Insulate underneath before anything else. A foot of compressed dry leaf litter, grass or boughs between body and ground is worth more than any roof. Conduction into cold ground is the fastest heat loss route available to you.
- Build small. A shelter is heated by the body in it; volume is the enemy. A debris hut should be barely larger than the person.
- Debris hut: one ridgepole from a stump or fork to the ground, ribs leaned along both sides, then a lattice of brush, then 60–90 cm of leaf litter piled over everything. Thickness is waterproofing; there is no other.
- Lean-to with fire reflector where you have fire and a group: an angled roof facing a long fire, with a stone or log wall behind the fire throwing heat back in. This is the warmest cheap option but burns fuel all night.
- Site on high ground away from the valley floor — cold air pools at the bottom, and that is also where the flood goes. Avoid dead standing trees overhead.
- Stay dry, and manage sweat. Wet insulation is not insulation. Strip layers before hard work, not after, so you do not soak your own clothes.
- Move to something permanent — see Permanent shelter — before the first hard season, not during it.
Doing it, step by step
The summary above says what has to happen. This says how, with the numbers that decide whether it works.
1 · Pick the site before cutting anything
Off the valley floor, out of dry washes, and not under dead wood. Cold air drains downhill at night and pools in the bottom, where it can sit several degrees colder than a bench partway up the slope — and the valley bottom and the wash are where flood water goes.
Look straight up before committing: a dead standing tree or a hung-up branch is the commonest way a good shelter kills its builder. Then look down: no ant nests, no animal trail, no hollow that will collect rain. Choose a spot with building material within 50 m, because hauling is the job that exhausts people.
2 · Insulate the ground first — at least 30 cm, compressed
Conduction into cold ground is the fastest heat loss route you have; lying on bare earth strips heat far faster than still air around you. Build the bed before the roof.
Pile dry leaf litter, grass, bracken or conifer boughs until, compressed by your full weight, it is still at least 30 cm thick — which usually means a loose pile of 60 cm or more. Boughs go in with the stems down and the tips up, overlapping like shingles. Keep material dry by gathering it before rain and stacking it under cover.
3 · Build the debris hut barely larger than your body
A shelter is heated by the body in it, so volume is the enemy.
- Ridgepole about your height plus 60 cm, one end on a stump or forked stake at hip height, the other on the ground.
- Ribs leaned against both sides at 20–30 cm spacing, steep enough to shed water — close to 45° or steeper. Inside width: your shoulders plus a hand's width either side.
- Lattice of brushy sticks over the ribs, so debris does not fall through.
- Debris — leaves, grass, bracken — piled 60–90 cm deep over everything. Thickness is the waterproofing; there is no other.
- A plug of debris or a stuffed bag to close the door from inside.
4 · Or build a lean-to facing a long fire with a reflector
Where you have fire and a group, this is the warmest cheap option — and it burns fuel all night.
- Roof: a crossbar at 1–1.2 m between two trees, poles laid back to the ground at about 45–60°, thatched with boughs or bark from the bottom up so each layer overlaps the one below.
- Fire: a long fire the length of the sleepers, about 1–1.5 m in front of the opening.
- Reflector: a wall of green logs or stacked stone 60–90 cm high, 30–60 cm behind the fire, throwing heat back in.
Gather the whole night's wood before dark, and then as much again — nobody finds firewood well at 3 a.m. See the fire guide.
5 · Manage sweat and wet — wet insulation is no insulation
Strip a layer before hard work, not after, so you do not soak the only insulating layer you have while building. Work at a pace that keeps you just below sweating. Change into dry clothes before sleep and keep one dry set for that purpose only.
Before sleeping: eat fat and carbohydrate, drink, urinate (the body spends heat keeping a full bladder warm), put on a hat, and sleep close to someone else. Wet clothing at 10 °C in wind is a hypothermia risk in a way that dry clothing at 0 °C in still air is not.
6 · Recognise hypothermia and rewarm correctly
The early signs are behavioural before they are physical: stumbles, mumbles, fumbles and grumbles — clumsiness, slurred speech, poor judgement, apathy. Violent shivering is mild to moderate hypothermia. Shivering that stops while the person is still cold is severe, and is not recovery.
Rewarm: get them out of the wind and off the ground, remove wet clothing, wrap in dry insulation with a waterproof layer outside, and put warmth — hot water bottles, warm bodies — against the chest, armpits and groin, not the arms and legs. Warm sweet drinks only if they are fully alert and can swallow. No alcohol, no rubbing, no hot bath. Handle a severely hypothermic person gently and keep them horizontal.
7 · Test it on a bad night, and fix what failed first
A shelter is proven by a full night in the worst weather the season has offered, not by how it looks at dusk.
If you woke cold, the problem is almost always underneath: add thickness to the bed before you add roof. If you woke cold on one side, the wall on that side is thin or the wind is getting in at the door. If you woke wet, the roof angle is too shallow or the debris too thin. Write down what failed and fix that first, one change at a time, and test again.
8 · Move to permanent shelter before the first hard season
Debris huts rot, compress and need rebuilding every few weeks; lean-tos consume fuel that has to be cut every day. Both are bridges.
Start permanent shelter while the weather is still good: a cob, log or stone building takes weeks to months, and earth walls need the dry season to cure before they meet a winter. A group that starts building in the first frosts spends the winter in a debris hut. See the building guide.