How Much Does It Cost For a Patio Installation?

The Paving slabs

There are a number of factors that affect the investment needed to create a great patio feature. Let’s start with the paving slabs.

Paving slab types

Porcelain The `go to’ paving material for a contemporary patio. These are non-porous and so are resistant to the build-up of dirt and algae. However, their fine finish and often light colour shows any muddy footprint or bird dropping. To look their best they need cleaning frequently and may not be the best choice for families with young children or dogs. Prices vary widely and this classy looking paving can be sourced at a lower cost than most good concrete slabs and at little more than Indian Sandstone.

Imported natural stone. Indian Sandstone evokes the look of traditional ‘York stone’ which is price-prohibitive for all but the most prestigious projects. It differs however in that colours vary widely within any given batch. This is a feature of the stone which you either like or not. It is a porous stone and so attracts dirt, algae and lichen and the original sometimes bold colours will fade significantly. Annual pressure washing is advisable and good quality Impregnating sealers can be used to mitigate weathering effects. Costs are a little less than standard porcelain and a lot less than premium porcelain. Other natural stones are available, such as black or yellow limestones towards the lower cost end and granite slate and Egyptian limestone at the higher.

Concrete paving. Budget price products tend to weather badly and if designed to emulate natural stone they look like what they are concrete moulds. Better quality offerings are more desirable and durable but can be more expensive than both imported natural stone and porcelain.

Brick pavers or setts can be incorporated into the patio design to great effect as a trim, cross hatching or infill panels. This can add a lot of time to the build and some pavers and setts are high cost so this will increase the overall budget of the project. They can also be used in isolation but that is a topic for another article.

So how will slab selection affect the cost of my patio? 

Not as much as you might expect, as the slab cost is typically only between 15% and 25% of the whole installation cost. Remember that a professional paving contractor has to factor in many other costs. These include labour, tools and equipment, disposal of spoil, a site loo, transport costs, project management and overheads. And then there is what goes under the paving slabs.

Foundations

This is a typical specification for a good installation:

Excavate to between 150mm and 250mm and remove all the spoil. Don’t be alarmed at this stage, you will have what looks like an archaeological dig going on in your back garden and a mountain of spoil in your front garden. A professional contractor should cover and protect all your access ways and spoil site so that this stage will pass without harm to your property.

Lay a porous barrier membrane. This stops the subsoil mixing with the foundation layer and weakening it.

Lay type 1 subbase (a specific blend of crushed stone which packs together tightly) and compact in layers to between 100mm and 150mm according to the soil conditions.

Less scrupulous or ill-informed contractors will skimp on this part and in so-doing reduce costs. This is a huge false economy as the highest quality paving materials laid on top of inadequate foundations will fail.

Bedding the paving

Modern materials have dictated changes in traditional methods of laying. For economy of transport, paving slabs are often much thinner. This can make them prone to discolouration through impurities leaching through from the bedding layer as well as a tendency to come loose as they don’t have the weight to help ‘hold them’ to the bed.

Don’t ‘Dot and Dab’. Some contractors lay slabs using the ‘dot and dab’ method – typically 4 or 5 splodges of mortar beneath each slab. The slab is then tapped down to level. This is quick and uses less material but leaves large air pockets beneath the slab and the jointing material is unsupported. Adhesion is compromised and the air pockets can fill with water. As a consequence the slabs come loose and the jointing material cracks and falls out. Even if they hold, the mortar bed contact points can show through as circular dis-colourations on the slab surface. This is another false economy!

Better contractors lay on a full bed which helps adhesion and the jointing material is supported. To aid the tamping down to level process, the bed is slightly underfilled and the mortar is then fluffed up with a trowel. This method has served many contractors well over the years but still allows water to accumulate in any small voids and the risk of discolouration remains.

And current best current practice? Slabs are laid on a completely full bed using a sharp sand:cement mortar. This prevents pooling of water in any voids. Sharp sand is more permeable than soft (builders) sand, and reduces moisture retention in the mortar. As sharp sand is less ‘sticky’ than soft, a special slurry bonding coat is applied to the back of the slab before laying.

What about those joints?

There are a number of ways to joint paving.

Sand/cement mortar is pressed into the joint and then ‘struck’ to a smooth finish. This traditional method is arguably still the best and also the most expensive method as it is time consuming.

Jointing Compound. An epoxy-resin two part compound is poured onto wetted slabs and ‘squeegeed’ in to the joints. This is more porous than mortar and has a coarse granular finish. Because of the porosity it can blacken with algae and dirt and so annual pressure washing is necessary. It is however strong and durable.

Polymer based jointing compounds. Less costly one part compounds which are not as durable and best avoided.

Extra care with Porcelain

Because these are relatively new to the market a lot of contractors lay these incorrectly. Firstly a slurry tack coat is absolutely essential as the impervious nature of the porcelain makes it hard to adhere to the bed. Joints should be narrow, aiding the clean contemporary look and filled with an exterior grout. The mortar bed must be allowed to dry before grouting. For best appearance, premium quality grouts can be colour matched to most porcelain colours.

Where does the water go?

A paving professional will always consider your property’s damp course levels and drainage. Best practice is to lay with an appropriate fall away from the house. For a larger area or where the adjacent ground is higher, a linear (or ‘Aco’) drain will be required and consideration given to managing the water discharged from that. Engineered drainage of this sort will add cost but is essential in some circumstances.

What else will I need?

Other features

Adding retaining walls and steps may add 50% or more to the cost of your patio.

To manage changes in ground levels, retaining walls and steps (Create link to page of same name on site) may be needed around your patio. These will add significant cost but also add interest and appeal . Be wary of the contractor that ‘fudges’ this aspect by raising the patio too close to the house damp proof course or laying with an inadequate fall or provision for drainage.

Good design

Good patio design advice is invaluable. Expect to pay a professional for this service if drawings are required.

Are you well informed? Do you know exactly what you want and have you considered all the pertinent factors? If so you can be prescriptive and instruct your contractor to build your feature exactly as you want it. Otherwise good advice from a professional is invaluable. If the installation is straight forward this may be part and parcel of a free quotation. If more complex or the feature is to be installed into a sloping area, investing in a paid design (Create link to Garden Designs page on site) will ensure all technical aspects are taken into account and the space is both functional and attractive.

So how does all this affect cost?

Many on-line pricing guides are based on ‘industry typical’ rates. Unfortunately the landscape trade is unregulated and bad practice is common. Prices stated in this guide are based on paving installed to Industry Best Practice Specifications supported by professional service. Here’s what you can expect:

Getting ‘best’ price

A patio professionally installed to industry Best Practice Specifications may cost twice as much as a poorly specified build but here’s the important bit: Your bargain price patio may need repointing in three years and relaying in five. Whereas, laid to best practice standards your pointing may need a bit of attention in five to ten years but your patio should last twenty.

So when choosing a contractor insist on seeing their full specifications and consider the true cost of your new patio over it’s lifetime. Using a professional contractor working to best, up to date specifications will be the best investment and represent the real best price.