Green Roof Construction-Structural Considerations

October 7, 2010 at 1:40 pm

Structural Support of the Green Roof

Excerpts from  Green Roof Construction and Maintenance,  by Kelly Luckett, 2009, published by McGraw-Hill’s GreenSource Books

Hi Green Roof Fans,

As one of the contributing editors here on Greenroofs.com – you may know me as “The Green Roof Guy” – I’m starting a series of excerpts from my book Green Roof Construction and Maintenance:

Rooftop Garden – Public Access
Having determined that the rooftop garden will be the place for people to gather and having provided access, one must ensure that the roof structure has the necessary structural capacity to support rooftop activity. Building codes may vary, so it is important to determine the local requirement for live loads and dead loads, and to understand how the green roof being built relates to weight requirement. The entire green roof assembly, including plants and the water required to saturate the growth media, is considered part of the dead load of the structure. Water in excess of that which saturates the growth media, snow and people visiting the green roof are all considered part of the live load of the structure. One must formulate a preliminary idea of what type of plants are desired and the proper growth media depth required to support them.

Saturated weight data should be available from the manufacturers of the intended green roof components. Typical rooftop gardens incorporate varying growth media depths and planters to support various plant choices. This will require calculations of the point loading of these various plant choices. Evaluating loading requirements and upgrading the structure to support  the green roof is easiest and most economical in the design phase of the construction of the building. Evaluating the structural capacity and making upgrades to an existing structure is significantly more difficult and more expensive. Many retrofit green roof plans die at this stage due to inadequate structural capacity and the prohibitive cost of upgrades. While there are some creative strategies of employing irrigation systems to reduce growth media depths in order to reduce dead loading, live load requirements could mean abandoning public accessibility to the rooftop garden and opting to design a simpler, extensive roof.

Green roof – No public access
When the green roof will not be a public gathering space, the live load structural requirements for the green roof are less complicated. Once the load requirements of the local building code have been determined, one must calculate the saturated weight of the green roof system to determine if structural upgrades will be necessary. Again, this is going to require some idea of the type of plants intended to grow on the green roof and the growth media depth required to support them. Typically the entire green roof will have a uniform dead load based on the saturated weight of the green roof assembly, though one may considering positioning planters or mounded growth media over structural support members to incorporate some strategically located deeper growth media for larger showcase plants. The plant palette is significantly expanded by increasing the growth media depth. As increased depth results in increased weight, there are often trade offs that balance structural cost with plant selection. Once the dead load of the green roof has been determined, a new structure can be designed with the required capacity. For an existing structure, one must begin by determining the structural capacity and design within those parameters. Irrigation systems have been successfully used to reduce growth media depth, and thus weight of the green roof system, for projects that would have otherwise required costly structural upgrades. For example, the green roof on the Ford Rouge Dearborn Truck Plant thrives in less than 3 inches of growth media and is sustained during periods of drought by the strategic use of supplemental irrigation.

Make sure to read my column, and to learn more about my company,  visit my website at:  http://www.greenroofblocks.com/  or send me an email to: GreenRoofGuy@greenroofs.com.

Kelly Luckett, A/K/A The Green Roof Guy

Calculators for Green Roof Construction

October 7, 2010 at 1:36 pm

Two Valuable Calculators Available for Planning:

Water Runoff Calculator and Green Roof Blocks Materials Estimator

Excerpts from  Green Roof Construction and Maintenance,  by Kelly Luckett, 2009, published by McGraw-Hill’s GreenSource Books

Hi Green Roof Fans,

As one of the contributing editors here on Greenroofs.com – you may know me as “The Green Roof Guy” – I’m starting a series of excerpts from my book Green Roof Construction and Maintenance.   As President of Green Roof Blocks, I’ve been involved in the industry since 1980, am a LEED Accredited Professional, and a Green Roof Professional (GRP).   Here we go:

Stormwater Runoff
Discussions of storm water runoff are typically concerned with the impervious surfaces within a certain development or a certain watershed.   Many municipal planning and zoning authorities have implemented policies restricting the amount of storm water runoff a new or existing development is allowed to generate. Some mandate no increase in the pre-development runoff volumes for new projects under consideration for building permits.

To help further promote green roof projects in the United States, we decided to make  our Water Runoff Calculator tool available free of charge.   The Excel based spreadsheet is available for download from the “Downloads and Calculators” page of the Green Roof Blocks website.

This storm water management tool quantifies storm water management values. Storm water runoff coefficients speak to the rate and volume at which water percolates into the ground rather than running over the ground’s surface. Where the surface of an undisturbed forest floor allows water to quickly be absorbed into the ground, a concrete or asphalt parking lot would instead repel water across the surface to lower neighboring grades. The difference in the permeability of the surface is sometimes referred to as imperviousness of the surface.

Green Roof Blocks Materials
Estimating materials well in advance of a project can be a challenge. Always contact the product providers for assistance and specifics. For example, we developed an easy tool to  help our clients using Green Roof Blocks and Green Paks- the Green Roof Materials Estimator, which is also  available at the “Downloads and Calculators” page of  our website. Assumptions in this Excel spreadsheet allow you to put in an advance date and receive an accurate estimate for your proposal based on that future time frame. Use this calculator to build multiple options based on your budget to present to your client. For questions, please contact us and we will be happy to customize a solution for your project.

Make sure to read my column, and to learn more about my company,  visit my website at:  http://www.greenroofblocks.com/  or send me an email to: GreenRoofGuy@greenroofs.com.

Kelly Luckett, A/K/A The Green Roof Guy

New Book from Ed Snodgrass Now Available!

September 7, 2010 at 1:03 pm

As you probably know (unless you’ve just entered the greenroof field), Ed Snodgrass is a horticultural consultant who  co-owns and operates Emory Knoll Farms/Green Roof Plants, a perennial nursery specializing in green roof plants that stocks over 100 varieties of green roof plants.   To date they have and provided over 2.5 million sf of planted roofs!

Ed also happens to be one of our Contributing Editors, our first in fact – see my 2009  “From Llamas to Greenroofs: An Interview with Ed Snodgrass.”   Appropriately, Ed is our Plant Editor and writes “Ask Ed” where he answers reader questions, writes occasional articles, and features seasonal greenroof plants for us.

Ed is also a seasoned speaker (highly in demand) and writer (who says he will try and contribute more here on Greenroofs.com!).     By now I’m sure you’ve all read  Green Roof Plants: A Resource and Planting Guide, by Edmund C. Snodgrass and Lucie L. Snodgrass, published by Timber Press, 2006 – I thought it was great, and a perfect resource – see my review here.

And, his brand new book, The Green Roof Manual: A Professional Guide to Design, Installation, and Maintenance, by Edmund C. Snodgrass and Linda McIntyre, published by Timber Press, 2010, is now available!   I feel privileged that I was sent an early copy to review, which I’m working on along with finishing up another Contributing Editor’s book by  Kelly LuckettThe Green Roof Guy Green Roof Construction and Maintenance, published by McGraw-Hill’s Greensource, 2009 (it’s fantastic and I can’t believe I haven’t finished the review yet).   Are they similar? Yes and no.   Both are certainly unique with dinstinct perspectives.

But my early feeling for Ed and Linda’s new book is that it is simply  great – much more overall in scope than the first (of course, it had a plant focus) and another must have for our greenroof and greenwall library!   Order today  from Amazon.com  for quick delivery.

Congratulations, Ed, on yet another success!

~ Linda V.

Happy Earth Day 2010!

April 22, 2010 at 11:15 am

Happy Earth Day 2010!   It’s the 40th anniversary of observing this date, and April has been unofficially dubbed Earth Month, too, in its honor.   April is also Landscape Architecture Month, a fitting selection for a profession so dedicated to respecting the Earth through responsible environmental design.

So how am I celebrating Earth Day and Month?   Well, you know we started our first annual “Love the Earth! Plant a Roof Earth Day Photo Contest”  – it’s open until April 28 for entering your favorite living roof and for voting.   By the way, there’s one clear early leader so far with over 200 votes!   Get your friends and colleagues to vote for your roof shot now.   We’ll announce the winner on April 30.

My hands-on project involves a local area  Daisy Troop – eleven young girls aged 7 and 8 who attend Birmingham Falls Elementary  in Milton, Georgia.   Their Girl Scout Leader, mom Sandra Nichols, contacted me a while back about speaking to the troop about the greenroof I designed at Rock Mill Park  in Alpharetta, GA.   The girls are working towards one of their badges, the  Clover Project, which involves preserving and protecting a local treasure and saving resources.   Since Sandra had been to the park before, she felt this would be a great learning opportunity to present the greenroof idea to the girls to educate them about saving water and reducing energy usage.

By the way, our Student Intern, Caroline Menetre – below, and I had just been up to the roof last week, doing routine weeding and taking notes to see which plants had fared well and which ones didn’t – more on that later.

Being a mom of three myself, and now a grandmom, of course I said yes!   I met with them this past Tuesday and had a blast speaking about rain water, stormwater, and an introduction to greenroofs to this lively and rambunctious group.   They especially loved touching all the plants in our four Greenroof Trial Garden tabletops – and they all got to try the garlicky Alliums in the Non-native Module!

I’ll be following up with them at their school this upcoming Tuesday to help them plant two 2′ x 2′ x 4″ greenroof modules of their own – both Green Roof Blocks and GreenGrid  donated a module each, which will be on display at the school for all the children to have hands-on experience and learn about different types of greenroof plants.   Thanks to Kelly Luckett of Green Roof Blocks, and Jim Lindell and Greg Harper of GreenGrid!   I should add a thanks to GreenTech as well – they offered their larger 4′ x 4′ x 8 1/2″ module, but it was decided  two smaller modules placed in two locations would better serve the students.

Also, Bobby Saul of Saul Nurseries  here in Atlanta and Alpharetta, GA, is donating the plants for both modules, as well as the growing media from ItSaul Natural.   After my little talk, I presented each girl with her own greenroof plant from Saul Nurseries to take home – a beautiful green  Jovibarba ‘Green Carpet’ –  succulent and spiky!   You know how kids like to touch things, well, they loved these!

I know that many of you are passionate about protecting the planet, and hopefully you are doing something this April to honor our land.   I’ll leave with this quote:

“Only within the moment of time represented by the present century has one species – man – acquired significant power to alter the nature of his world.” ~ Rachel Carson

~ Linda V.