Sunday, February 6, 2011

Extensive Green Roof Cost - How much should a living roof cost?

How much do we need?

Mercedes or Volkswagen?  Cadillac or Ford?

I'm not referring to quality because, in my opinion there is quality in each.

I'm referring to the 'custom extras' (including the value in the brand name).

Same way with a living roof.  One of my close roofing contractor friends a couple of years ago became really excited about getting into the green roof business because he saw a huge profit margin.  At the time a satisfactory green roof system, not including the underlayment or TPO layer was selling for around $20 to $25 per square foot.

Of course, the system he was considering was not basic, rather more mid-level in complexity and components.  There was a frame, a drainage mat, a water adsorption pad, another woven mat, the soil and potted plants.  But still, he felt he could make $12 or so per square foot even with the labot to install, insurance and his overhead.

That adds up to a profit margin of about $240,000.00 on a 20,000 SF roof.

Considering the other extremes;
  • A complicated green roof system with multiple layers, or trays where the profit margin may be only $2 per foot for a total margin of $40,000.00 or
  • A very simple system with a root barrier/liner, mat, soil and seeds where the profit margin could be $16 per square foot for a profit of $320,000.00 
Extremes usually don't happen, yet the point here is valid.  How much do we really need?

Green roofs have come along ways since the first sod roofs.  Some systems today are engineered to control almost every environmental variable.

But how much of all the technology and plastics and plastic trays and plastic liners and adsorbent mats and plastic weave and ground up rubber tire crumb anti-pollution media, and all else that goes into a green roof do we really need?

When do we start creating GMO plants specifically designed for green roofs and rooftop garden environments?  When do we start growing roboplants?

How about back to basics.

A simple extensive green roof should cost no more than the following:
  • A strong root barrier/liner - 20, 40 or 60 mil depending upon application Cost: $ 0.60 per square foot
  • Adhesive $0.30 per square foot
  • A woven mat or honeycomb type fabric system, something to hold the soil in place (if you really want to be sustainable and cost-effective use hemp or burlap instead of a polyethylene weave) typical mat cost $ 0.60 per square foot
  • Best Gro-Drainage Soil Mixture  $ 1.00 per square foot
  • Seeds (C3,C4 and CAM native & food plants) cost $ 0.60 per square foot
  • Labor to install $2.00 per square foot (probably high)
  • Overhead, insurance, etc cost $ 1.00 per square foot 
Total Cost $6.10 per square foot for a quite nice system.  Note: This price does not reflect cost of just one manufacturer.  There are many great systems choices on the market so always shop around for the best price.

Sure, many sales reps will try and sell you the high end system.

Yet how much do we really need?

There are some beautiful vegetated roofs that have lasted for centuries across Europe without layers and layers of high tech plastics.

On a side note, the 60 square foot rabbit hutch roof I built this weekend at $25 per square foot would have cost $1,500.

My cost breakdown was:

  • Root barrier/liner 60 sf @ $0.50 sf $30.00
  • Grow mat 60 sf @ 0.50 sf $ 30.00
  • DIY Soil Mix 60 sf @ 2" $5.00
  • Seeds - Lots of Veggies! $ 5.00
  • Labor - mine
Total cost $70 for a green roof (little over a buck per square foot) that will look every bit as good as the most expensive green roof in the world and last as long and provide food at the same time. For a photo refer to the blog here.

How much do we really need?


Joanne Barragan said...

Some people think that for them to have their own green roof, they need to spend a lot of money on it, but the truth is you don’t need to! You don’t have to make it look complicated and feel like it’s beyond your reach. You can start by putting green grass or by moving around some decorative plants that you already have in your garden. Little by little, you may add other plants that will make your green roof more beautiful.

Sam Gerrard said...

Extensive green roofs are the most popular choice for many homeowners because of their light weight and low irrigation needs. Sedums, grasses, and other green roof plants can grow on them with a minimum of fuss, and with little need for maintenance.

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Roofers Bronx said...

What an interesting read, thanks for sharing!

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