Cost to Build a Shed Base

Expert Advice + We Look at DIY Options

Written by Daniel Woodley. Fact checked by Hannah Miller. Published to Prices. Updated: 4th March 2023.

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Your spanking brand new shed isn’t going to last very long if it starts to subside into the ground, and you won’t find a material more suited to supporting the shed than concrete (although there are some DIY alternatives discussed here too).

I have plenty of experience in building shed bases and here you’ll find a realistic price guide.

I’ll also look at the DIY option, how to lay the base and how much the materials cost.

Constructing a Shed Base

The general consensus among landscape gardeners and builders is that a concrete garden shed base should be around 75-100mm thick and should have an additional 75mm sub-base made from compacted hardcore.

It should also have a sheet of weedproof membrane laid under it to stop weeds from growing through.

That’s how I and all the tradespeople I’ve previously worked with have built shed bases.

Here are the steps most professionals, including myself, take when constructing a concrete shed base:

  • Clear area of vegetation.
  • Excavate the ground to around 150mm depth.
  • Treat the soil with a weedkiller to kill off any roots of weeds if required.
  • Compact the soil, if required.
  • Shutter the edges with timber boards.
  • Lay and compact hardcore to 75mm depth.
  • Lay a weedproof membrane/sheet.
  • Pour concrete mix to a minimum depth of 75mm.
  • Allow 2 days to dry.

Concrete Shed Base Cost

Below is a price table based on typical shed sizes. The figures are for a professional to dig out the foundation, shutter the edges and lay a sub-base, weedproof membrane and a concrete finish.
Base Size:Items:Lab:Total:
2.5 sq metres (a very small shed)£110£400£510
4.5 sq metres (med size shed)£200£550£750
7.5 sq metres (large size shed)£320£750£1070

The prices shown above are an average of the figures provided to me by a selection of landscape gardeners in the UK – rather than what I would charge. Some of the prices supplied to me were higher, while some were lower.

To get a firm quote, tap the button below and fill in the contact form:

You May Pay More If…

No two projects are identical, and the prices above are for a standard concrete shed base.

Based on my experience, you’ll probably pay more if:

Access is difficult – If your chosen contractor has to carry all the materials through the property because there is no direct access to the rear garden, then the project will take longer and cost more.

Non-standard excavations – if the ground is made from concrete or tarmac or is filled with roots, then I’ve found that the excavation will probably take longer and cost more.

Uneven ground level – if the ground is very uneven and needs to be filled with a significant amount of material, then I’ve found that this will add to the cost (both materials and labour costs).

Unusual ground conditions – I’ve worked on projects where the ground was very soft, and we had to build a sub-base and concrete top layer that was much thicker, costing more. I have experienced this issue on projects before, and the cost of additional concrete significantly added to the cost.

Worker removing cavity wall insulation

Can a Shed Be Constructed on Patio Slabs to Save Money?

Sheds should only be built on a solid foundation as this prevents subsidence, which I’ve seen cause:
  • Cracked glass.
  • Cracked timber.
  • Damage to fixings.
  • Doors jamming.
  • Damage/cracks to the roof felt.
In my opinion and based on my experience, sheds should never be built directly onto the soil or on slabs or pads placed directly onto the soil. I have seen countless shed sink because the slabs shifted and this usually leads to the shed buckling. A concrete base is the best option, although slabs can be placed on top of the concrete for aesthetic purposes if required.

The DIY Option (+ A Cost Estimate)

Those with experience in DIY can construct shed bases, I’ve seen many competent DIYers do it. You’ll need the following:
  • Tape measure.
  • Shovel.
  • Trowel.
  • Spirit level.
  • Hammer and nails.
  • Timber for the shuttering and smoothing the surface (25mm planks).
  • Safety PPE.
  • Cement.
  • Sand and aggregate.
  • Concrete mixer and whacker hire.
  • Buckets.

How to Construct a Shed Base From Concrete

Start by excavating the ground to a depth of 150mm, and slightly deeper if the ground is soft. Compact the ground by using the whacker or stamping on it. Using the tape measure and pegs, mark out where the shed base will go. Construct the shuttering using the 25mm planks, saw, hammer, nails and spirit level. The planks should be pegged every metre to prevent them from bending. Lay the hardcore to a depth of around 75mm and compact it with a whacker or mix in some sand and stamp on it. Lay the weedproof membrane and overlap well if the shed base is large. Mix the concrete in the mixer; 1 part cement, 5 parts ballast (sand and aggregate), and water. Add fibres for reinforcement if the shed will be used to store anything heavy such as a motorbike, gym weights/equipment etc. Pour the concrete, starting in one corner and continue until slightly higher than the top of the timber shuttering. Using a 25mm plank or any other material with a straight edge, tap the concrete repeatedly to remove any air gaps and compact it. Now level the concrete with a sawing motion, pushing off any excess concrete. The edges of the slab can be smoothed off with a trowel to leave a neat finish.

Cost Estimate For DIY Concrete Shed Base Construction

Below is a price guide for the DIY construction of a concrete shed base.

The price assumes the sand and cement are purchased in bags, a cheap weed membrane, some timber for shuttering, and the hire of a concrete mixer and a whacker for one day.

Hand tools and waste disposal are not included in the estimates below.

I researched these prices and believe them to be correct but obviously, prices change over time:

Item:Approx Price inc VAT
Electric mixer and whacker hire (1 day)£50
Ballast and cement per sq metre at 75mm depth£30
Hardcore per sq metre at 75mm depth£10
Shuttering (25mm timber)£40-80 depending on size of area
Weed membrane£1.50 per square metre

Alternatives

The most popular DIY alternative I’ve seen is a grid base. The grids are made from plastic and are 40mm thick, the installer should place them into the ground fill them with pea shingle. As the grid spreads the weight of the shed, they are unlikely to subside and are perfect for smaller sheds and DIYers. Would I use a grid like this? No, I would pay a little extra and get a concrete base down, as I feel this would last longer and leave a neater, more professional finish. However, if you’re on a budget, you may find this video informative:

6 Questions Expertly Answered

Here are answers to 5 common questions: Is planning permission required?  In most cases, no. However, if the shed is very large or tall, it would be prudent to consult your local planning authority, which will probably have helpful information online. There are height, width and location limitations and separate rules may apply to conservation areas. What is the best depth for a concrete shed base? I’ve never had any issues with a standard 75mm of sub-base and 75mm of concrete poured on top, but I’ve increased this to a total of 200mm if the shed will store heavy items or the ground is unusually soft. What is the best sand/cement ratio for a concrete shed base? A mix of sand and cement will likely crack once dried, so aggregate (stones) must also be added to the mix. The most popular ratio is 1 part cement to 5 part ballast (a mixture of sand and stones of various sizes). Should I use reinforcing fibres? Fibres can be added to the mixer; they are cheap and help prevent cracks from appearing in the concrete as it dries, but they are optional. I’ve never felt the need to use them for shed bases, but I’ve seen others use them. How long does it take for the concrete to dry? I’ve always found it best to leave the concrete for 48 hours, although it will be safe to walk on within 24 hours. What is a fair price to pay for a garden shed? Garden sheds cost from £750 (small, basic) up to £2000 (larger, more complex) and beyond. On this page, I discuss the complete cost to buy and install a new garden shed, including a base.

Get a Custom Price for Your Concrete Shed Base

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Why You Can Trust Us: Our Research & Methodology

In January 2023, I sourced prices from 18 landscape gardeners in the UK and calculated an average cost per square metre of concrete shed base.

The price examples shown on this page are based on the average price I obtained.

The information regarding DIY methods, mixes, thicknesses, alternatives etc, is based on my experience within this industry – I used to work for a landscaping firm before I moved into project managing landscaping developments on a larger scale.

Author: Daniel Woodley

Daniel has over 18 years of experience in the construction, home improvement, and landscape garden industries, including a spell working as a project manager.

In his spare time, Daniel enjoys gardening, hiking and scrambling. He frequently posts videos to his popular YouTube Channel and is well known in the hiking community.

More About Daniel Woodley.

Daniel Woodley

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