What will it cost to create a level patio in a sloping garden?

We often get asked ‘what will it cost to create a level patio in a sloping garden?’ If you have a steeper site – particularly with the ground sloping up away from the house, there will be a requirement for some careful planning if you want level space adjacent to your home but don’t want to look out on massive retaining structures.

A recent client came to us with exactly this question – the current patio is very degraded and on 2 levels, with a 60cm step in the middle and a whole range of slopes and steps – not ideal for a contemporary feel or for small children and entertaining!

The lawn continues to slope up beyond the patio towards the rear of the property, probably rising another 1.8m from the top of the existing retaining structure to the rear of the lawn. The client would like to create some level play space in the lawn if possible to make more use of it.

The Process

Whilst it is tempting to dive into how to make this look gorgeous (and that is eminently possible!), in plots like this there is typically a question of budget and priorities.

Under any reasonable assumptions for the design there will be a need for:

• Around 50 sqm of new paving
• Significant excavations to level the patio and remove existing structures- around 50 cubic metres if it is fully levelled
• New drainage works (there appears to be none in the current walls which is probably whey they are failing)
• Around 35 linear metres of retaining walls at 60cm high (exact configuration will need a structural engineer to design)
• Levelling of a section of lawn of around 60 sqm and preparation and returfing of approx. 160 sqm

Our suggestion was that before diving into creating some gorgeous design for the rear garden that may well be totally unaffordable, we should create a simplified scale model of the plot and work out a possible arrangement of the levels. This allowed our costings gurus to work out a top-level budget for the proposed works so that we can frame the design priorities accordingly. There is no point in the client paying for a proper survey and a full design if they can only at this stage afford to do the main patio. Similarly, if even that is not affordable, then the budget should be spent on making the existing patio attractive and safe.

The Simple Design

We created a simple 3D model of the plot based on photos, a site visit, and google earth plans. We then designed an arrangement of this to capture steps and walls where required, keeping all drops to less than 60cm (this is the maximum allowed under building regulations without adding balustrades). This isn’t intended to show the best possible arrangement of the space, nor a beautiful plan at this stage, but gives us the square metreages we need to run the costings. The dark green areas are intended for planting areas to create a barrier to children running off the edge of the lawn, without making this a high visual block when viewed from the house. The levelled section in the lawn is to be created with banking around it rather than retaining structures to minimise the costs, and is approximately halfway up the lawn so that the “cut and fill” are approximately equal- limiting the amount of spoil to be removed and soil to be brought in. Access is adequate although we may need to remove part of a wall to the side of the house and create a ramp to allow digger access.

We then came up with a second and lower cost option leaving the patio in 2 levels, thereby reducing the amount of excavation, the scale of the retaining walls, and removing the uncertainty of excavating the section currently banked up against the house (which we assume will need a new finish and remediation after excavation).

So what will it cost to create the levelled patio?

Using the second option, The budget cost to do this we estimate to be £63,550. The breakdown is shown below:

Prelims – £15,250

• site mobilisation
• welfare
• machinery
• Deliveries
• Health and safety

Site clearance and excavations – £8,500

Retaining walls in brick – £16,000

Paving in sawn sandstone – £21,400

Hedging/planting – £2,400

This is obviously simple, assumes access is adequate, and does not allow for additional drainage, lighting etc.

Next steps

Having shared this with the client, they can then make an informed decision as to how to proceed. A proper topographic survey will be required to allow us to more accurately design and cost the proposed works, and this will cost around £950 (plus VAT).  The design will cost £3,500 plus VAT, and this will allow us to create a more considered version, maximising the budget including planting, lighting and detailing, as well as providing a detailed cost breakdown based on real site conditions.

A few things to note when creating a level patio in a sloped garden:

• When the slope rises away from the house, the more level space you want to have, the higher the retaining walls will need to be (ie the ground is higher further away from the house). This means more steps as well as more walling and patio and hence more cost
• The higher the retaining wall, the more visual impact there is from the house- avoiding the sense of looking out onto a large wall is key- either by creating tiers or dressing the walls attractively
• All drops should be kept to under 60cm where at all possible to reduce or remove balustrading
• Even at 60cm, a small child, animal or even adult could be hurt if they fall, so creating at least some visual barriers -hedging or planting- is desirable

Conclusion

Levelling adjacent to a house can be a costly business. Retaining walls and steps need to be created, and drainage must be considered carefully to avoid flooding in the lower sections. It must be planned very carefully to ensure that the resulting garden is as beautiful and as practical as can possibly be achieved within any chosen budget. Exploring the design solutions in 3D is essential to understand the impact of making changes to the geometry of the design and the desired results.

If this is something you are keen to explore, there are a few other articles we have written covering costs of landscaping and design, as well as a more detailed explanation of levelling options on lawns and many other useful tips – see Insights

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