Skurfundamenter

Et skurfundament uden beton

Plant, fast og frit drænende på en eftermiddag. IBRAN-gitre giver et skurfundament, der holder gulvet tørt og konstruktionen i vater, uden blanding, forskalning eller ventetid på hærdning.

Hvorfor fundamentet betyder mere end skuret

Skure svigter næsten aldrig på grund af selve skuret. De svigter på grund af det, der er nedenunder.

Sæt en trækonstruktion direkte på jord, fliser lagt i sand eller et par blokke i hjørnerne, og to ting sker. Undergrunden bevæger sig, så rammen vrider sig, døren holder op med at lukke, og taget slipper vand ind. Og fugt samler sig mod bærerne, fordi intet nedenunder dræner, så gulvet rådner nedefra, mens væggene stadig er intakte.

En betonplade løser bevægelsen, men skaber sit eget problem: den er uigennemtrængelig, så vand, der rammer den, skal et sted hen, og det ender typisk som en pøl rundt om kanten, der holder træet fugtigt alligevel. Det er også en dags arbejde, en betonblander, en leverance af tilslag og et fundament, der er der for altid, uanset om du vil have det eller ej.

Et gitterfundament løser begge dele. Indesluttet skærver giver en fast, plan platform, der ikke sætter sig ujævnt, og hele konstruktionen forbliver fuldt permeabel, så regn dræner direkte igennem og luft cirkulerer under bygningen frem for at fugt samler sig mod den.

Velegnede anvendelser

Haveskure fra 6x4 og opefter
Værksteder og hobbybygninger
Cykel- og plæneklipperrum
Brænde- og skraldespandsrum
Plast- og metalskure
Hønsehuse og dyrehuse
Opstillingsplads til olietanke og udstyr
Udskiftning af en defekt plade eller belægningsfundament

Overblik

Bærelag	75-100mm kompakteret stabilt grus til et typisk haveskur. Mere til et værksted eller tungt indhold
Fyldmateriale	6-14mm gradueret blanding, kantet og rent, fyldt i niveau med cellernes overkant
Samlet udgravning	Ca. 110-140mm afhængigt af gitterdybde og bærelag
Tid	En eftermiddag for et typisk skurfundament, én person
Værktøj	Spade, rive, håndsav og en komprimator, hvis du lejer en
Dræning	Fuldt permeabelt. Vand dræner igennem frem for at samle sig rundt om bygningen
Designlevetid	25 år, forudsat dokumenteret udførelse
Materiale	100% genanvendt polypropylen, fremstillet i EU af genanvendt plast

Hvorfor det slår alternativerne

Mod en betonplade: ingen blanding, ingen forskalning, ingen hærdetid, ingen bortkørsel af overskudsjord, og ingen permanent konstruktion tilbage, hvis skuret fjernes. Det er også betydeligt billigere for en typisk havebygning, når man medregner tilslag, cement og leje af udstyr.

Mod belægningsfliser: fliser lagt i sand sætter sig individuelt, og når én falder, følger hele bygningen med. Et gitterfundament fordeler belastningen over hele fodaftrykket, så platformen forbliver plan som én enhed.

Mod trælægter på blokke: blokkene synker ned i blød jord med forskellig hastighed, og mellemrummene samler blade og fugt. Et sammenhængende fundament gør det ikke.

Mod ingenting: dette er den mest udbredte løsning for haveskure og årsagen til, at så mange skurgulve er bløde i hjørnerne.

Hvilken gitterdybde?

Nummeret på et gitter er en beslutning om, hvor dybt det indesluttede stenlag er. Til havebygninger er belastningerne beskedne og fordeles via bærere, så den laveste løsning er normalt den rigtige.

IBRAN®-X30 til de fleste haveskure. Den laveste udgravning, mindst sten og mindst overskudsjord at komme af med, hvilket betyder noget, når den eneste adgang til baghaven er gennem huset.
IBRAN®-X40 til større værksteder, tungt indhold eller hvor fundamentet også bruges som adgangsvej for trillebør eller plæneklipper.
IBRAN®-X50 hvor et køretøj skal køre op på fundamentet, f.eks. en garageagtig bygning eller et plæneklipperrum med regelmæssig adgang.

At specificere større dybde end et skur kræver, er sten, du har betalt for at grave ned og bære ned i haven.

Valg af sten

Brug en 6-14mm gradueret blanding, kantet og ren. En lavere celle kræver en finere maksimal kornstørrelse for at fylde helt ud, og en blanding pakker tættere end en enkelt størrelse, fordi de mindre sten fylder hullerne mellem de større.

Den tæthed er det, der giver dig en plan, stabil platform. En fuldt fyldt celle fører belastningen gennem stenene og ned i undergrunden; en halvfyldt celle fører den gennem plasten i stedet, og under en bærer, der bærer et hjørne af bygningen, viser det sig som en sænkning.

Undgå rundet havegrus, som ruller frem for at låse sammen, og alt med finstof eller støv, som binder overfladen og forhindrer dræning. Dræningen er halvdelen af det, du køber.

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Recommended for this project

Plastic Shed Base Grids

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How it goes in

Mark out the base. Make it larger than the shed footprint by at least 100mm on every side, so rain running off the roof lands on stone rather than on soil next to the timber.
Check the ground falls away from the building position rather than towards it, and clear any turf, roots and soft soil down to firm ground.
Excavate to your total depth: sub-base plus grid depth. For a typical garden shed that is around 110-140mm.
Lay a woven geotextile across the dig, lapping joins by at least 300mm and taking it up the sides. This stops the sub-base mixing into the soil beneath and keeps the base performing.
Add the sub-base and compact it. 75-100mm of MOT is ample for a garden shed, compacted in one or two layers rather than tipped and levelled.
Blind with a thin layer of grit sand and screed it level. Check it with a straight edge and a spirit level in both directions: this is the layer that decides whether your shed door shuts.
Push-fit the grids together across the base, cutting the perimeter to line with a hand saw.
Fill the cells with a 6-14mm graded blend, level with the cell tops, and brush it in so no cell is left hollow.
Set the shed on bearers across the base and check it is square and level before fixing anything together.

Full step-by-step detail is in our installation guides.

Make the base bigger than the shed

This is the single most useful thing to get right, and it costs almost nothing at the time.

A shed roof throws water off its edges. If the base stops at the shed footprint, that water lands on soil, splashes soil back up against the boards, and keeps the bottom of the building permanently damp. Extend the base 100mm or more beyond the shed on every side and the runoff lands on free-draining stone instead, where it disappears.

The margin also gives you somewhere to stand while you build, somewhere for the door to swing over, and a clean strip to walk round the building for maintenance rather than treading a muddy path into the lawn.

If the shed has a door on the long side, take the base out further on that side still. It becomes the threshold you stand on every time you open it.

Keeping the floor dry

Rot in a shed floor almost always starts underneath, and it starts because moisture has nowhere to go.

Set the building on bearers rather than directly on the base, so there is an air gap under the floor. Run the bearers in the direction that lets air pass through, keep vegetation cut back from the sides, and resist the temptation to pile logs, bags or bin bags against the walls, which traps damp exactly where the timber is most vulnerable.

With a permeable base, water that gets under the shed drains away and air moves through. That combination is what keeps a timber floor sound for decades rather than years.

Sloping gardens

Few gardens are flat, and a shed base has to be.

For a gentle slope, dig into the high side rather than building up the low side. Cut-and-fill is fine for the last little bit, but material you have added is always less stable than ground you have not disturbed, so take more off the top than you put on the bottom.

On a steeper slope you will need a retained edge on the high side, and it is worth stepping back and checking whether the shed wants to be somewhere else. A level spot ten feet away is usually cheaper than a retaining structure.

Get it right first time

The one thing worth knowing: level and square, checked twice.

Almost every complaint about a shed comes back to the base not being flat. The door binds, the windows will not shut, the roof panels do not meet, and the building racks slowly out of shape.

Screed the blinding layer properly, check it with a straight edge in both directions and diagonally, and check the diagonals of your marked-out area match before you lay a single grid. Ten minutes with a spirit level and a tape saves a decade of a door that never quite closes, and unlike everything else on this list it cannot be fixed once the shed is up.

Ask our engineer

Questions about depths, base sizing, sloping ground or which system fits your building? Ask below, or get in touch directly.

Common Questions

Things that frequently come up when carrying out this project.

Is a grid base as good as a concrete shed base?

For a garden building, better in most respects. Confined stone gives a firm level platform that spreads load across the whole footprint, and unlike concrete it stays fully permeable so rain drains through rather than pooling round the building and keeping the timber wet.

There is no mixing, no formwork, no curing time and no permanent structure left behind if the shed goes.

How deep do I need to dig for a shed base?

Around 110mm to 140mm in total for a typical garden shed, made up of 75mm to 100mm of compacted MOT sub-base plus the grid depth. Larger workshops or heavy contents need more sub-base.

It is a shallow dig, which matters when the spoil has to be carried through the house to get out of the garden.

How big should a shed base be?

Larger than the shed footprint by at least 100mm on every side. A shed roof throws water off its edges, and if the base stops at the footprint that water lands on soil and splashes back against the boards. Extending the base means runoff lands on free-draining stone instead.

Take it out further still on the door side, since that becomes the threshold you stand on.

What size gravel should I use for a shed base?

A 6mm to 14mm graded blend, angular and clean. A blend packs tighter than a single size because the smaller stone fills the gaps between the larger, and that density is what gives a flat stable platform.

Avoid rounded pea shingle, which rolls rather than interlocking, and anything carrying fines, which binds the surface and stops it draining.

Which grid depth do I need for a shed?

The 30mm grid suits most garden sheds: the shallowest dig, the least stone and the least spoil. Use 40mm for larger workshops, heavy contents, or where a wheelbarrow or mower route runs up to the base.

Use 50mm only where a vehicle will drive onto it, such as a garage-style building.

Do I still need bearers under the shed?

Yes. Set the building on bearers rather than directly on the base so there is an air gap under the floor. Rot in a shed floor almost always starts underneath, and it starts because moisture has nowhere to go.

A permeable base drains water away and bearers let air move through, which is the combination that keeps a timber floor sound.

Can I build a shed base on a slope?

Yes. For a gentle slope, dig into the high side rather than building up the low side, since material you have added is always less stable than ground you have not disturbed.

On a steeper slope you will need a retained edge on the high side, and it is worth checking whether a level spot a few feet away would be cheaper than a retaining structure.

How long does a shed base take to lay?

An afternoon for a typical garden shed, working alone. The grids push together by hand with no tools or fixings, and the base is usable immediately: there is no curing time, so the shed can go up the same day.

Most of the work is the digging.

Do I need planning permission for a shed base?

Garden buildings are usually permitted development subject to size, height and position limits, and a permeable base does not add to surface water run-off in the way an impermeable slab does.

Rules differ across the UK and are tighter for listed properties and conservation areas, so check with your local planning authority if you are unsure.

Can I put a grid base over an existing slab or paving?

Yes, provided the existing surface is sound and water has somewhere to go. Fill any holes, check your finished levels, and use the shallowest grid to keep the build-up down.

If the slab is badly broken or holds water, it is usually better to lift it, since a base that cannot drain gives up the main advantage of the system.