How Much Do Green Roofs Cost?
Calculating the average cost of green roofs can be difficult because there a number of variables, not just the size and accessibility of the site but the types of plants that are going to be grown on it. A large scale green roof on top of an exclusive London high rise might cost hundreds of thousands, whereas the small garden you have on your garage may have cost as little as £500 if you have done it yourself.
Here are the main factors that affect the cost of a green roof:
- An intensive green roof generally costs more than an extensive one, because of the deeper soil.
- The cost will inevitably rise if you need to employ a landscape gardener to design the roof for you, which is normal for larger installations.
- Accessibility plays a big part in the construction costs. A green roof on a skyscraper is going to set you back more than a garden where the roof is easy to get to.
- The degree of structural engineering required if you roof needs to be strengthened is also another cost factor in green roofs.
- The quality and quantity of the plants and other garden materials adds to the bill.
- Something like a biodiversity or brown roof may require more ongoing maintenance than other kinds of installation.
As a very rough indication, in the United Kingdom one can expect to pay around £100 per meter squared of extensive green roof, and around £150 per meter squared for the intensive variety. These figures will vary, however, and green roof installation companies will be able to give you a clearer figure based on your site’s specifications.
Unlike renewable energy technologies such as solar, wind, hydro, and heat pumps, there are currently no UK government grants to help with the initial cost of installing a green roof. This may change in the future, however, as green roofs become more and more popular in this country.
In addition to the initial cost of designing and installing green roofs, there are also running costs which need to be taken into consideration, such as maintenance and regular gardening.
Domestic Green Roofs
Domestic green roofs can come in at a fairly competitive price if you know what you want and like to design the outlay yourself. Where the greater expense will come in is if you want to employ the services of a landscape gardener to design the look, choose the plants and everything else. For a small area that could bump the cost up from just a few hundred to a few thousand.
One aspect to also consider when you are looking at green roofs on your home is the potential savings on fuel bills because of the extra layer of insulation. If you add on that you are extending the lifespan of your roof by installing a green roof, then the benefits begin to add up.
Maintenance costs for domestic green roofs tend to involve the replacing of plants and doing the gardening work, which you can pay someone to do or undertake yourself if you are a keen horticulturist.
If you are planning a DIY project and buying the raw materials for installation and building the garden yourself, for a site that is 8 m² you would be looking at a cost of between £500 and £800. For the same project using a qualified installer you should probably add anything from another £500-£1,000.
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Commercial Green Roofs
Green roofs for businesses and large commercial premises will normally need some kind of design input that will add to the cost of the installation. The types that have been designed and built by the top landscape artists can stretch into the millions but for an average business premises it can be anything from the same cost as a domestic green roof to something that costs in the thousands.
A lot will also depend on the accessibility of your roof – houses have the benefit that they are normally only two floors up and accessible by ladders, whilst your business may be higher up which will add cost because of the trouble in getting the materials to the site.
People to Contact if you are installing a Green Roof
You may well get away with not contacting the right people but it pays, as we always say, just to check your plans with the following people:
- The council – green roofs should fall into the category of permissible builds but some councils have certain caveats that you might be falling foul of.
- Check with your mortgage provider as they may be concerned about the effect your green roof is going to have on your house value (there’s no current research that says there is a detrimental effect).
- Check with your building’s insurer, simply because you are adding extra weight to the roof and they will need to be informed of any change to the building structure.
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