What does it cost to level a garden?

A frequent question for us is “what does it cost to level a garden?” If you have a sloping garden and would like a stretch of level lawn for football or entertaining you may like to know roughly what it will cost to create that space. It can make the garden feel larger or just more useable, depending on quite how the space is configured and can be a great investment. In this blog, award-winning designer Vicki Davis and Landscape Project Manager Phil Howard share their insights into the costs and considerations of levelling.

What does it cost to level the lawn?

Phil Howard works on costing projects including levelling all the time, and his first answer is “it depends”. When pushed to give us a rough cut he worked out some examples for us to share..

Levelling a lawn about the size of the one in the image above (around 100 sqm) from a slope of 1 in 8 (i.e. a gradient of 15.5%) in the Home Counties….

• Simple with no retaining from £5,000 plus VAT
• Basic with retained edges from £14,000 plus VAT
• Elegant with simple steps and planting from £17,500 plus VAT

We work through the geometry and assumptions in these below. It is however really important to note that these are likely to be a minimum cost. There are numerous factors that can increase the totals significantly and we discuss these below too!

Effect of increasing the slope:

Increasing the slope makes a massive difference to the likely costs, doubling the angle to a 1 in 4 slope (25% gradient) would increase the walls to 2m, making it a much more complex engineering task and increase the cost by a multiple of 3-4 times.

All of these figures are incredibly sensitive to the specifics of the site geometry, access, soil type and final finished design.

Worked examples:

1) SIMPLE LEVELLING – NO RETAINING

Key assumptions: Level the 100sqm of lawn, assume cut and fill (i.e. match as far as possible the amount dug out to the amount built up), banked edges (no retaining) and say 10% waste out, losing the rest on site.

This makes no allowance for what happens around the edges of the levelled section- at its lowest cost this can be graded into the surrounding levels if space allows but there is still a cost to this. Soil decompacts/bulks on excavation so there is likely to be an excess to be removed (we have allowed for 10%), and new topsoil will probably be required before the lawn can be laid.

COST – Simple with no retaining from £5,000 plus VAT

2) BASIC RETAINED LAWN

Key assumptions: As for example 1 but add in 40 linear metres of retaining walls up to 1m high.

 In reality a 1m retaining wall is not ideal in a garden as building regulations require balustrade for walls above 60cm- there are some stepped solutions, but this adds more cost, and is not necessarily required if not working under building regs where planting could be used to protect from falls if desired. There is also no stepped access.

COST – Basic with retained edges from £14,000 plus VAT

3) MORE ELEGANT APPROACH

Key assumptions: As for example 2 but add in additional levelling and sculpting in upper area to allow for steps to sit outside level lawn and 35 sqm of planting. Add steps.

This is a more realistic garden scenario although we still have 1m retaining that needs consideration.

COST – Elegant with simple steps and planting from £17,500 plus VAT

What drives the costs of levelling a lawn? (and what might increase them)

There are other key factors that could drive the costs to increase substantially- and not many that will bring them down (but see “design solutions” below) Here are some of the more common variables that can impact the costs.

Site Geometry

Seeing the diagrams above, you can see that retaining structures are usually required, and these are expensive. The larger (longer and higher) these are the more the cost increases. If the site is larger and we can “lose” the spoil elsewhere and use banks rather than retaining this can help, but it does extend the area that needs to be restored/sculpted.

If the slope is steeper the walls will be higher for a given area levelled, and the waste quantity out will be higher. There will pretty much always be some waste out as soil de-compacts when excavated, and the more you are digging the more is likely to need to come out, even if you have tried to balance the cut and fill.  For larger walls (taller than around 1.2m depending on circumstances) a structural engineer is likely to be required to make the required calculations and the wall construction will no doubt be more expensive. You also will then need to consider the drainage behind the wall more carefully, and of course how to clad or hide the wall which will become a very imposing feature.

Walls above 60cm require balustrade under building regulations, and these might be desirable anyway for safety reasons- glass balustrade is a great choice in a garden, but is expensive (allow at least £600 per linear metre, plus an allowance for construction of whatever it is to be fixed to), there are some good examples here

Site Access

This is a big one – moving large quantities of soil requires large machinery to be carried out efficiently. If the landscapers cannot get a good-sized digger in, the work will take longer and therefore cost more. Awkward access, tight manoeuvring space and steps will require some shenanigans to achieve the desired results- it is often cheaper to take down a fence or wall to give access than to work around it.

The driveway and road access are also important as larger lorries are required to take spoil out as cost effectively as possible.

Soil / Ground Conditions

Claggy clay soils and flint/stoney ground are much harder to work with. Heavy clay soils often have drainage problems that then need to be sorted out. Free draining soils are usually easier but can require temporary retaining structures once dug out. Different soil structures react differently to excavation, and bulk up when excavated. Therefore, they will create a different cubic meterage when dug and this can be pretty hard to predict!

Tree Roots

Working around existing trees requires careful planning- bear in mind that the “root protection zone” (RPZ) around a tree is typically the size of the canopy plus 20% not just the trunk. If the tree is protected with a Tree Preservation Order (a TPO) we are not permitted to excavate or raise the soil level within the RPZ. Even if not protected, whilst we have a little more leeway, it will compromise the health and longevity of the tree if the levels are changed. There is a more technical discussion of this here.

DESIGN SOLUTIONS

Given some of the eye-watering costs highlighted here, we asked Vicki Davis, Design Director at CGLA for her few suggestions for improving the effectiveness of levelling and for reducing costs where possible.

Use the existing slopes as much as possible and consider breaking up the walls.

Most sites have more level areas, working around these can make a big difference to the amount of work required. Working this out in advance using 3D modelling and a detailed topographic survey will allow you to cost as accurately as possible, and to review your options in the context of your desired results. This is particularly important when planning a new build house or extension.

Vicki says “clients can be very surprised indeed when we model a new build house at the level that it is proposed, and they see the scale of the retaining walls that can be required to create a large level patio behind the house. Dressing or hiding the walls, creating multiple levels, and making features of the steps can all make a massive difference to how the space feels- looking out of your lovely bifold doors onto a huge wall with a balustrade on top of it is rarely a good solution!”

Hide banking in planted areas and use walls as features where possible.

Where space allows, use retaining structures for built-in seating or dining areas, and hide sloped gradients with planted banks.

Keeping as many walls to below 60cm as possible increases your options of avoiding balustrades and makes the space feel more open. Try to use larger walls as decorative features- sculptures, green walls and attractive cladding can all make these feel like they are part of the garden.

Make the steps an elegant part of the design

Steps can be large clunky features, so using a lighter solution is great. These ones from our friends at Adezz are a good option, and come in a range of prefabricated sizes

SUMMARY

Levelling is rarely a cheap option unfortunately. If you are simply looking for a football zone within a larger site, then a basic job of levelling can be done, using banks to the edges, and avoiding retaining walls. You will still need good machinery access and to consider the drainage and final surface required. Where you would like a formal lawn or level patio space it is best to consider the project in terms of the garden as a whole- how will the levels relate to the rest of the space and how can you get the absolute best effect for the required investment.

In our experience, a well-planned series of levels within a garden can make an astonishing difference to the space as a whole, and can add considerable value to a property. However, if you have a steeply sloping garden and tight access it can become uneconomic to create significant levelled areas, and you may be better off working broadly with what you have, levelling some smaller areas for seating and decorative lawn to maximise the features of the garden and improve access to the whole space whilst minimising steps, retaining, and costs.

All of these options can be discussed and considered within a garden design process, but it will be helpful in refining your choices to have an idea of the likely costs before you embark!

CGLA are an award winning team of Garden Designers, Landscape Architects, Landscapers and Garden Maintenance Operatives working in Buckinghamshire, London and the South East, as well as on prestigious design projects across the UK and abroad. We are currently working in Oman, Jersey and France, and welcome enquires for design, landscaping or garden maintenance. Contact us here