An ice house is a drained, shaded and heavily insulated pit or outbuilding that holds winter ice through the summer. Dig a pit 2-3 m deep and 2-3 m across on a well-drained north-facing slope, slope a gravel floor to a drain, leave a 15-20 cm insulation gap behind the wall lining, roof it with a ventilated air gap, and enter through a double door. Water that pools around the ice melts it far faster than air does, so drainage matters more than any other detail.
Part of Ice Houses and Cold Storage
A building whose only job is to keep ice from melting between the winter harvest and the summer demand. The same structure appears as an outbuilding in Storage Buildings Design, alongside the granary and smokehouse.
An Ice House Must Lose Heat Slowly And Meltwater Quickly
Ice stored in a building melts because heat reaches it from the ground, the walls, the roof and every open door, and because the water that forms conducts heat and carries it around the stack. A good design attacks all of those at once: shade and a north-facing site reduce solar heat, the ground and a buried pit supply a cold surround, insulation slows conduction through every face, a vented roof sheds the heat that gets through, and drainage removes meltwater before it can sit against the blocks.
This page is the build sequence. If you came from an outbuildings or storage-planning page, the same structure works above ground (see the section on the above-ground variant), but below-grade is the best performer, and the rest of the child pages explain each part: Below-Grade Design, Meltwater Drainage, Roof Design and Insulation Methods.
What You Need
- Site — a north-facing slope in the Northern Hemisphere, well drained, close enough to the settlement for easy access, and away from fires, compost and south-facing walls.
- Digging tools and labour — a pit of this size is several days of work for a small crew.
- Gravel — 20-30 cm for the floor.
- Wall lining — dry-stacked stone, brick or timber.
- Insulation — sawdust, straw or dried leaves for the wall gap, and sawdust or straw for packing the ice. Sawdust is the classic choice.
- Roofing — thatch, shingles or any roofing material, and timber to frame two layers with an air gap between them.
- Drain — a pipe or channel leading to a soakaway downhill of the ice house.
Method: Build The Pit Ice House In Order
Step 1: Choose the site. Pick a shaded north-facing slope with water that can run away downhill from the pit. Test the soil as in Soil Drainage Capacity; a pit in clay with no outlet becomes a bucket.
Step 2: Dig the pit. Dig 2-3 m deep and 2-3 m in diameter. Cut the walls straight or slightly sloped inward; a crumbling wall will fill the pit.
Step 3: Make the floor. Slope the floor toward a drain channel at the centre. Lay 20-30 cm of gravel. Lead the drain through a pipe or channel to a soakaway downhill. Meltwater must leave the pit without a path for warm air to enter.
Step 4: Line the walls. Build a dry-stacked stone, brick or timber lining, leaving a 15-20 cm gap between the lining and the earth. Fill that gap with sawdust, straw or dried leaves. Keep the fill dry; wet fill conducts heat and rots.
Step 5: Frame the roof. Build a peaked or domed roof over the pit, extending at least 60 cm beyond the walls on all sides. Use two layers, an inner ceiling and an outer roof, with an air gap between them so heat can ventilate away.
Step 6: Hang the doors. Make a small door, 60 cm x 120 cm, facing north and insulated. Add a second door with a 60 cm vestibule between them so that opening one never exposes the ice to outside air. Seal the edges with cloth or rope caulking.
Step 7: Load and seal. Pack the ice as described in Ice Stacking, and close the doors until ice is needed.
Worked Example: How Much Ice A Pit Actually Holds
The parent article states that a 2-3 m pit holds roughly 8-15 cubic metres of ice, and that a community of 20-30 people needs roughly 5-10 cubic metres for a full summer. This check shows why the pit’s gross volume is not the ice volume.
Inputs: diameter 2.5 m, depth 2.5 m, and an assumed 17.5 cm of insulation on the sides, floor and top (the mid-point of the parent article’s 15-20 cm).
- Gross volume of a cylinder: pi x (2.5 / 2)^2 x 2.5 = 3.1416 x 1.5625 x 2.5 = 12.3 m3.
- Ice diameter after insulation on both sides: 2.5 - 2 x 0.175 = 2.15 m.
- Ice height after insulation top and bottom: 2.5 - 2 x 0.175 = 2.15 m.
- Ice volume: 3.1416 x (2.15 / 2)^2 x 2.15 = 3.1416 x 1.1556 x 2.15 = 7.8 m3.
So a 2.5 m pit gives about 7.8 m3 of ice. At the parent article’s 900 kg/m3 that is 7,020 kg, which sits inside the 5-10 m3 range a 20-30 person community needs, but leaves little margin for melting. Larger pits lose a smaller share of their ice because there is less wall area for each cubic metre of ice.
The Above-Ground Variant For Sites That Cannot Be Dug
Where bedrock or groundwater prevents a pit, build the ice house as a double-walled timber or masonry outbuilding with the same insulation gap, the same drained gravel floor and the same ventilated roof, and pile earth against the walls at least 60 cm thick. It performs worse than a pit because the ground no longer helps, so lean on thicker insulation, shade from trees or a hillside, and the double door.
Common Mistakes
- No drainage — meltwater that pools around the ice melts it much faster than air does. Use the gravel floor, the sloped channel and the outfall pipe.
- Wet insulation — damp sawdust or straw conducts heat and can rot, so keep the wall gap dry and the roof sound.
- Skipping the airlock — each time a single door opens, warm air displaces cold. Build the vestibule.
- Building on a sunny south slope — direct sun on the structure is the largest external heat source.
- Treating the gross pit volume as the ice volume — see the worked example above.
Safety
A closed pit with rotting plant material can have too little oxygen
Wet sawdust, straw, hay and leaves keep decomposing in a sealed pit, using up oxygen and releasing carbon dioxide. Carbon dioxide is heavier than air and settles at the bottom, so the air at the top of the ladder can feel normal while the air at the floor cannot support life. A person who climbs down can collapse within a few breaths and the person who goes down to rescue them can collapse too. Never lower a flame, candle or lantern to test the air: it cannot be relied on, and a flame in a pit full of dry sawdust and straw is a fire. Instead, open the hatch and doors and force fresh air to the bottom of the pit with a long duct and a bellows or fan before anyone goes below, keep ventilating while anyone is below, tie a line to the person descending, and keep an attendant at the top whose only job is to haul the line and never to climb in. If the person below slows, sways, sits down or goes quiet, pull them out by the line.
An open pit and a heavy hatch cause injuries
A pit 2-3 m deep is a fall of two to three times a person’s height. Keep the door or hatch latched, use a fixed ladder, and fence the pit during construction.
What’s Next
- Learn next: Below-Grade Design — how deep to dig and what the ground contributes
- Learn next: Meltwater Drainage — keep water out without letting heat in
- Combine with: Ice Stacking — pack the pit once it is built
- Combine with: Ice Cellar — a second treatment of the same structure