6x4 Shed Bases

Which shed base kit fits a 6x4 shed?

Start with the shed rather than the kit. One sold as 6ft x 4ft is rarely exactly that, so find the size of its floor in the listing, work in metres and pick a platform the same size or a little bigger.

Each ProBASE grid is 500 x 500mm and 40mm deep, so a finished base grows in half-metre steps. A typical shed this size measures about 1.8 x 1.2m. Lay the squares 4 long and 3 wide and you get a 2.0 x 1.5m platform from 12 of them, with a margin of 10cm or more all round. That's exactly what Shedstore's own kit for this size holds.

The squares lock together on all four sides, so a kit's name doesn't fix its shape. Three packs on this page suit a shed this size or the ones either side of it:

• 6x5 kit, 16 squares. Lays 2.0 x 2.0m. Use 12 for the 4 by 3 base and lay the last row of 4 in front of the doors as a dry step.
• 10x3 kit, 12 squares. Sold as a 3.0 x 1.0m strip for narrow stores, but it holds the same 12 pieces. Clip them 4 by 3 instead, then trim the membrane and overlap the pieces.
• 5x5 kit, 9 squares. Lays 1.5 x 1.5m. Too small here, but right for 4x4 and 5x3 sheds.

Facing the doors on a long side? A 4x6 shed base is the same 12 squares turned round. The maker shows more layouts on the ProBASE website.

6x4 shed bases compared

Here's how the small ProBASE kits line up. Platform is the size of the base laid as the kit intends. Gravel is the total at the 15kg per square Shedstore advises. Prices move daily (the grid above always shows today's price), so they're in bands here.

Every pack is the same system with a different number of pieces, and each box holds the same three things:

• Interlocking squares of recycled plastic, each 500 x 500 x 40mm. Lightweight to carry but strong and durable once filled.
• A heavy-duty membrane, commercial grade, to stop weeds coming up through the base.
• A 2 year guarantee, plus full instructions that show you how to assemble the base.

The stones aren't in the box. Shedstore recommends 10mm pea gravel, and 12 squares take about 180kg, so a few bags from a garden centre do it. Delivery of the kit is free to most mainland postcodes, as Shedstore's delivery terms state. Some Highland and island areas are outside its delivery zone, so put your postcode into the delivery checker before you order. The kit arrives flat-packed for home delivery, and the driver can't carry it through the house.

Our small sheds and the base each one needs

These are the listed sizes of the small sheds we stock, with the grid layout that covers each one.

The Skylight 4x6 is the classic 6ft x 4ft model in our range and sits on 12 squares. The 6x3 is the one to watch. At 1.85m long it needs a 4-square run, which the 5x5 kit can't give it, so the 10x3 pack is the one. Both Skylight models come with an anchor kit, so fix them down once the gravel is in. Browse them on our small plastic sheds page.

5x4, 7x4, 6x5 and 7x5 shed bases

The sizes either side of a 6x4 work the same way.

• 5x4 shed base. About 1.5 x 1.2m, so lay 3 by 3 (1.5 x 1.5m). That's the 5x5 kit exactly.
• 7x4 shed base. Around 2.1 x 1.2m, just over a 4-square run, so lay 5 by 3 (2.5 x 1.5m, 15 pieces). The 6x5 kit covers it with one to spare.
• 6x5 shed base. The 6x5 kit lays 2.0 x 2.0m, which suits most 6x5 and 6x6 sheds.
• Bigger sheds. For 8x6, 8x7 and 7x5 models see our 8x6 shed bases. For workshops, the 10x8 shed bases page covers the large kits.

How to lay a 6x4 shed base

One person can lay a base this size in an afternoon. Most of that time goes on the ground. The kit itself is quick and easy to assemble, with no concrete to mix and no special tools.

1. Mark out an area a little bigger than the platform with pegs and string. For a 2.0 x 1.5m base, mark about 2.2 x 1.7m.
2. Strip the turf and any soft topsoil, then rake the soil flat.
3. Compact the ground firmly. On clay or soft soil, tamp down a thin layer of hardcore or sharp sand first so nothing settles.
4. Check it's flat both ways with a spirit level on a straight board.
5. Roll out the membrane and overlap any joins so weeds can't find a gap.
6. Clip the squares together on top, working out from one corner.
7. Fill every cell with pea shingle, brush it flat and check it again.

Spread any spare stones as a strip around the walls. It works as a simple french drain for drainage, so rain runs away instead of splashing mud up the panels.

The maker also sells anchor blocks that sit in place of the infill. You screw the timber floor frame of a garden building to each one, which stops a light shed shifting in high winds. They aren't in the kits here, so buy them separately if you want them.

Why a small plastic shed needs a level base

Plastic and resin sheds are fussier than timber ones. The wall panels slot into the floor, so if the base dips the frame twists, the doors stop meeting and panels can work loose. Even a shed with its own floor needs a flat surface under it, as our plastic sheds with floors page explains.

A filled plastic base keeps things dry too. Water drains straight through the open cells and air moves under the floor, so damp can't sit against it. A small shed is light enough to catch the wind, so fix it down with ground anchors from our shed security range.

Other ways to build a base for a small shed

A plastic grid isn't the only route. Here's how the usual options compare at 6ft x 4ft.

• Wooden shed base. A pressure treated timber frame you screw together. Forest Garden's measures 118 x 182.6cm, is UC4 pressure treated for ground contact and carries a 15 year anti-rot cover, though it's made for Forest's own sheds. B&Q lists several pressure treated wooden shed bases at 180 x 118cm. On damp ground timber can still rot in the end.
• Paving slabs. Six 600 x 600mm slabs make 1.8 x 1.2m, which is tight, so most people lay 8 or 9. Each needs bedding, and one rocking slab shows up in the floor.
• Concrete slab. The most permanent foundation, but 2.0 x 1.5m at 75mm thick still takes about 0.23 cubic metres of concrete, plus formwork and days to cure. A lot of work for a small store.
• Adjustable base. On a slope or an uneven old patio, steel brackets level a timber frame without digging. QuickJACK Kit 1 is listed for sheds from 4x3 to 6x5, including 6x4. The hard surface version adjusts up to 100mm and the soft ground one up to 150mm, both with a 10 year warranty. You supply the timber. See our adjustable shed bases.

So why choose a plastic shed base kit over slabs or timber? It's quick to install, with nothing to set. The pieces push together by hand, won't rot, and you can lift the whole base and reuse it if you move. The same kits suit a small summerhouse, a greenhouse, a pressure treated timber garden building, a log store or a wheelie bin store just as well. For a summerhouse, check the floor size and pick the kit the same way.

You'll also see similar kits from other brands at B&Q, Fastfit among them. Check the square size, whether a membrane comes in the box and the cover before you compare prices.

Do you need planning permission for a 6x4 shed?

Almost never in England. A garden building is permitted development if it stays behind the front of the house, is single storey and covers no more than half the garden. Within 2m of a boundary it can be no taller than 2.5m, which a 6x4 shed sits well under. The Planning Portal guide to outbuildings has the details, and the government's permitted development technical guidance explains how height is measured.

A 40mm plastic base adds very little to that height. Listed buildings, flats and conservation areas have extra rules, and Wales, Scotland and Northern Ireland set their own.

6x4 shed base FAQs

How many squares does a shed this size need?

Twelve, laid 4 long and 3 wide for a 2.0 x 1.5m platform. That leaves a margin of 10cm or more around a typical 6ft x 4ft shed.

How much gravel will I need?

About 180kg for 12 squares, at the 15kg each Shedstore recommends. Get a little more for a strip around the walls.

Do I have to fill the squares?

Yes, for these kits. Shedstore's listing for every pack recommends filling each one. It adds weight and strength and locks the base in place.

Can I lay a shed base straight onto grass?

Not straight onto turf. Strip the grass and soft topsoil, compact the ground and check it's flat, then lay the membrane and the squares. If you can't dig, an adjustable base for soft ground is the alternative.

Is a 4x6 shed base different from a 6x4?

No. It's the same 12 squares, turned to match which way the doors face.

What guarantee do the kits have?

Each kit sold by Shedstore has 2 years' cover. The recycled plastic won't rot, so a well-laid base should last far longer.