Field Shelter Bases
A shelter base that drains, and does not make the building permanent
Field shelters need firm, level ground that sheds urine and wet bedding. IBRAN grids do that without pouring concrete, so the shelter stays clean, dry and, where it matters, still movable.
Why the base matters here
A field shelter is a small building doing a hard job. Horses or stock stand in it for hours in the worst weather, on the wettest ground of the year, in the one spot they have all chosen at once.
Put that on bare ground and it poaches within weeks. The floor becomes a mix of mud and bedding that cannot be mucked out properly, urine has nowhere to drain so it sits in the surface and the ammonia builds, and the doorway turns into the deepest hole on the holding because every animal passes through it.
Concrete solves the floor and creates two new problems. It is impermeable, so urine and wash-down have nowhere to go except across the surface and out of the door. And it is a permanent structure, which for a shelter that is meant to be mobile can be the difference between something that needs planning permission and something that does not.
A grid base gives a firm, level, cleanable floor that drains straight through, holds bedding rather than swallowing it, and can be lifted and moved with the shelter if it ever needs to go somewhere else.
Where this works well
- Mobile and skidded field shelters
- Static field shelters and loose boxes
- Shelter aprons and entrance areas
- Livestock shelters and calf hutches
- Hay and feed store bases
- Ring feeder and trough standings
- Muck heap bases and approaches
- Standing areas beside a shelter
At a glance
| Sub-base | 150-250mm compacted MOT, more on soft or wet ground |
| Infill | 6-14mm angular graded blend, clean and free of fines, filled level with the cell tops |
| Total dig | Around 200-300mm, depending on ground conditions and grid depth |
| Drainage | Fully permeable. Urine and wet bedding drain through rather than sitting on the floor |
| Bedding | Firm level surface that holds shavings or straw and mucks out cleanly |
| Movability | No poured structure. Grids can be lifted and reinstated if the shelter moves |
| Design life | 25 years, subject to documented installation |
| Material | 100% recycled polypropylene, made in the UK |
Mobile shelters and the permanence question
This is worth understanding before you build anything, because it can change what you are allowed to have.
Mobile field shelters are often treated differently from permanent buildings, on the basis that they are genuinely movable and are not fixed to the ground. Standing one on a poured concrete slab, or bolting it down to a permanent foundation, can undermine that argument and reclassify the shelter as a permanent structure.
A grid base is not a poured foundation. It is a compacted, confined stone surface that the shelter stands on, and it can be lifted and relaid elsewhere. For a mobile shelter that is usually the more appropriate answer, as well as the more practical one, because you can move the shelter for ground rotation and take the base with it if you want to.
Planning treatment varies by authority and by circumstance, and it depends on the shelter, the land and how it is used rather than on the base alone. If there is any doubt, ask your local planning authority before you build. It is a short conversation and a considerably better one to have first.
Which grid depth?
The number on a grid is a decision about how deep the confined stone layer is. Shelters combine standing animals with occasional heavy vehicles, so err deeper than you would for a garden building.
- IBRAN®-X50 is our recommendation for the entrance apron, and for the whole base where a tractor tows the shelter, mucks it out, or delivers bedding.
- IBRAN®-X40 for the shelter floor itself where handling is done by barrow and fork rather than machine.
- IBRAN®-X30 where you are laying over existing hard standing, or a level has to match an adjoining yard.
If in doubt, take the heavier option at the doorway. That is where every animal stops, turns and stands, and it is where any base fails first.
Choosing your stone
Use a 6-14mm angular graded blend, clean and free of fines, filled level with the cell tops.
The graded blend matters more here than almost anywhere. A blend packs tighter than a single size because the smaller stone fills the gaps between the larger, and a densely packed surface is a stable one: nothing rolls underfoot, nothing works loose under a hoof, and bedding sits on top of a solid floor rather than sinking into it.
Keep the stone fine and angular rather than large or rounded. Loose or oversized stone can move under a hoof, bruise a sole or lodge in a shoe, and in a shelter the animal is standing on it for hours at a time.
Keep fines out entirely. Anything carrying dust or scalpings will bind, hold urine and water in the surface, and give you the ammonia problem you built the base to avoid.
How it goes in
- Choose the position carefully. Shelters want to sit on the driest ground available, with the back to the prevailing wind and the opening away from it, and with somewhere for water to go that is not the doorway.
- Mark out the base well beyond the shelter footprint, taking it out furthest at the opening. The apron outside the door is not optional: it is where the wear actually happens.
- Dig the mud out down to firm subsoil. Poached ground has no bearing capacity, and anything laid on it will sink into it over one winter.
- Lay a woven geotextile across the formation, lapping joins by at least 300mm. On soft ground it is structural, stopping the sub-base punching down and stopping soil pumping up into your surface.
- Lay and compact the sub-base in 50mm layers, to a depth that suits the ground and the vehicles that will come to the shelter.
- Blind with a thin layer of grit sand and screed it level, with a slight fall away from the shelter towards the opening or to one side.
- Push-fit the grids together, staggering the joints. Cut to line around skids, posts and the door opening with a saw.
- Fill the cells with a 6-14mm angular graded blend, level with the cell tops, brushing in thoroughly so no cell is left hollow.
- Set the shelter in position and check it sits level on its skids or bearers before it is used.
Full step-by-step detail is in our installation guides.
The apron outside the door
If you only reinforce one part of a shelter site, make it this.
Every animal using the shelter passes through one opening, and most of them stop in it: half in, half out, watching the field, standing in the same spot for hours. That doorway takes more traffic and more standing time than the whole of the rest of the field put together, and it is the first place to poach.
Take the base out at least a shelter's depth beyond the opening, and wider than the opening on both sides. Where a group shares the shelter, take it further still, because the animals that cannot get in will stand as close as they can and churn the ground doing it.
Get the falls right at the same time. Water running off the shelter roof lands exactly here, and if it has nowhere to go it will undo the work.
Bedding, mucking out and drainage
A permeable base changes how the shelter works day to day.
Urine and moisture drain down through the stone instead of soaking into bedding and sitting on the floor, which keeps the bed drier, reduces ammonia and means bedding goes further. There is no low corner collecting liquid and no wash of muck out through the doorway.
Mucking out is easier because you are working on a firm, level surface: a fork does not dig into the floor, and a barrow wheels rather than sinks. Where a tractor and bucket do the job, specify the deeper grid across the whole floor so the base takes the machine as well as the animals.
Where drainage from a shelter could reach a watercourse, ditch or borehole, check what applies to you before building. Rules on managing run-off from areas used by livestock vary and are worth confirming with your local authority or environmental regulator.
Anchoring and wind
Field shelters blow over. They are large, light, and usually in the most exposed spot on the holding.
A mobile shelter on skids relies on its own weight and its skids bedding into the ground, and a firm level base makes that behaviour more predictable rather than less. Where the manufacturer specifies ground anchors, these can fix through the base into the compacted sub-base beneath, which is another reason to compact that layer properly rather than tipping and raking it.
Follow whatever the shelter manufacturer specifies. It is their structure, and their anchoring recommendation accounts for its size, shape and exposure in a way that generic advice cannot.
Get it right first time
The one thing worth knowing: build the base bigger than the shelter.
A base that stops at the walls solves the floor and leaves the real problem untouched. The mud simply forms at the threshold instead, and everything then walks through it to get inside, dragging it onto the clean floor you just built.
Extend the base out into the field at the opening, round the sides where animals shelter from wind, and to wherever a barrow or tractor comes and goes. The extra area is the cheapest part of the job and it is what turns a dry shelter into a dry shelter you can actually reach.
Ask our engineer
Questions about depths, apron sizing, drainage or which system suits your shelter? Ask below, or get in touch directly.
Common Questions
Do I need a concrete base for a field shelter?
No, and for a mobile shelter concrete is often the wrong answer. A grid base gives a firm, level, cleanable floor that drains straight through rather than holding urine and wash-down on the surface, and it is not a poured foundation, so it can be lifted and relaid if the shelter moves.
It is also considerably quicker to build and needs no curing time.
Will a concrete base make my mobile field shelter permanent?
It can affect how the shelter is treated. Mobile field shelters are often treated differently from permanent buildings on the basis that they are genuinely movable and not fixed to the ground, and standing one on a poured slab or bolting it to a permanent foundation can undermine that.
Planning treatment varies by authority and circumstance, so ask your local planning authority before building if there is any doubt.
How deep should a field shelter base be?
Around 200mm to 300mm in total, made up of 150mm to 250mm of compacted MOT sub-base plus the grid depth, with more on soft or wet ground.
Dig out to firm subsoil first: poached ground has no bearing capacity, and anything laid on it will sink into it over one winter.
What stone should I use in a field shelter base?
A 6mm to 14mm angular graded blend, clean and free of fines, filled level with the cell tops. A blend packs tighter than a single size, and a densely packed surface is a stable one, so nothing rolls underfoot and bedding sits on a solid floor rather than sinking into it.
Keep the stone fine and angular: loose or oversized material can move under a hoof, bruise a sole or lodge in a shoe.
How far should the base extend beyond the shelter?
Take it at least a shelter's depth beyond the opening and wider than the opening on both sides. Every animal passes through one doorway and most of them stand in it, so that spot takes more traffic and standing time than the rest of the field put together.
Where a group shares the shelter, extend it further, because animals that cannot get in will stand as close as they can.
Does a permeable base help with bedding and ammonia?
Yes. Urine and moisture drain down through the stone instead of soaking into the bedding and sitting on the floor, which keeps the bed drier, reduces ammonia and makes bedding go further.
There is no low corner collecting liquid and no wash of muck out through the doorway.
Is it easier to muck out than bare ground?
Considerably. You are working on a firm level surface, so a fork does not dig into the floor and a barrow wheels rather than sinks.
Where a tractor and bucket do the job, specify the deeper 50mm grid across the whole floor so the base takes the machine as well as the animals.
Which grid depth should a field shelter use?
The 50mm grid for the entrance apron, and for the whole base where a tractor tows the shelter, mucks it out or delivers bedding. The 40mm for the shelter floor where handling is done by barrow and fork. The 30mm where you are laying over existing hard standing or matching an adjoining yard level.
If in doubt, take the heavier option at the doorway.
How do I anchor a field shelter on a grid base?
Follow the shelter manufacturer's recommendation, since it accounts for the structure's size, shape and exposure. A mobile shelter on skids relies on its own weight and its skids bedding in, and a firm level base makes that behaviour more predictable.
Where ground anchors are specified, they can fix through the base into the compacted sub-base beneath, which is a further reason to compact that layer properly.
Can the base be moved with the shelter?
The grids can be lifted and reinstated, which suits ground rotation or a shelter that changes position.
Bear in mind the excavation and sub-base stay behind, so the reusable element is the grid itself rather than the whole build-up.
Ask our engineer
Questions about depths, sub-base, edging or which system fits your project? Ask below.
