Structural requirements for a green roof

Although historical and archaeological evidence suggests that green roofs have been built for more than three thousand years, widespread acceptance has always been limited by the structural cost of supporting heavy soils and by the technical challenges of lowslope waterproofing. A green roof is a green space created by adding a growing medium and plants on top of an existing or new roofing system. You can read more about the system structure for a flat green roof below. Investigate the feasibility of the installation of a green roof. The structural design of the building will embrace the specification of the appropriate waterproofing system to meet the demands placed on it by the green roof and the effects of climate, especially with regard to performance against highwind. Thus, they have more substantial structural loads and need more frequent maintenance and watering. The planning, implementation and maintenance of all these types is covered in the uk green roof code of practice. Guidelines for the planning, construction and maintenance of green roofs the fll green roof guidelines guidelines for the planning, construction and maintenance of green roofs were developed from the principles for green roofing published in 1982 and have been revised several times since 1990. Structural roof strengthening to support new green roofs. The modern greenroof movement began in germany in the mid1970s. What is a green rooftechnical preservation services. The modern green roof movement began in germany in the mid1970s.

Green roofs are usually held in place just by the weight of the growmedium. Design guidelines and maintenance manual for green roofs in the semiarid and arid west. The allowable depth of the green roof is determined by the load capacity that can be allocated to it. Review the submittal requirements for the green buildings ordinance detailed above. The planters on a roof garden, on the other hand, can generally range anywhere from 6 in up to 3 ft 0. We have designed green roofs from anywhere between 30 to 200 psf. Green roof or rooftop garden requirements and plant list. With a reputation for quality, safety, client satisfaction, and efficient project delivery, structural has been called upon to help solve some of the. The term green roof is a catchall for any roof with vegetation on it and is also sometimes referred to as an ecoroof. Structural enhancements are not necessary for vegetative roof installations over most concrete decks.

A green roof is composed of multiple layers which may include a waterproofing roof protection layer, moisture interception layer. Introduction to types of green roofs on buildings in cities. Structural roof strengthening to support new green roofs by tarek alkhrdaji i n the race to build green, many building owners and contractors have turned to an unlikely place. The appropriate depth of any green roof depends on the roof structure, the plants chosen, annual rainfall, and stormwater performance requirements. Design criteria for green roofs minnesota stormwater manual. How to select the type of green roofs you should employ on your project 3. Height of the green roof systems which will affect upstand requirements weight range of each system which may determine the structural support you need maintenance needs for green roofs, and. German green roof technology is migrating into the us.

Green roofs can be limited by the additional weight of the fully saturated growing medium and plants, in terms of the physical capacity of the roof to bear structural loads. Intensive green roofs require the deepest soil and have the greatest impact on the structural design, but they also accommodate all types of plantings including large shrubs and trees. According to webster dictionary is the outside top covering of a building or structure that protects, shelters or. A green roof can retain up to 75% of overall rainwater, and this can often result in a need for structural reinforcement.

For building permits, also fill out the forms and consult the submittal checklists in the commercial building permit guide pdf. They are recognized as a bench mark set of guidelines for green roofs in germany. The structural requirements for a green roof are the most important aspect to consider. A structural engineers advice is essential to ensure comprehensive design development, based on the buildings construction, condition and weight loading capacity. Its proponents were interested in creating green space in otherwise barren urban areas. With a reputation for quality, safety, client satisfaction, and efficient project delivery, structural has been called upon to help solve some of the most challenging issues with industrial infrastructure. Which are the structural components that form a green roof.

Be careful suppporting on wood joists even if joists work when checked under this additional load possible issues with rot, longterm creep is there a gypsum ceiling below. The fll green roof guidelines guidelines for the planning, construction and maintenance of green roofs were developed from the principles for green roofing published in 1982 and have been revised several times since 1990. A structural engineer should verify that the roof will support the weight of the green roof system. For secondary wall members supporting formed metal siding, the design wind load deflection shall not exceed l90 for roofs, this exception only applies when the. The important technical issues which must be addressed 5. Extensive vegetative roofs wbdg whole building design. All green roof codes of practice globally are based on the german fll. Green roofs are structurally engineered and generally comprise of six key components as illustrated in the figure bellow. Planning green roofs and green walls structural design. Due to the specialty of this type of garden, a structural engineer and a landscape architect familiar with this unique habitat should both be consulted. Green roof in the deserttempe transportation center roof garden, dr.

Container gardens on roofs, where plants are maintained in pots, are not generally considered to be true green roofs, although. Are the application requirements the same for all green roofs. To learn more about the application of geofoam for green roofing, you can download our green roof pdf see how geofoam makes a large green roof possible on a parking deck in chicago maggie daley park. Because water runs off the roof more quickly, a thicker substrate layer is needed. Determine the portion of roof that will have a green roof.

For secondary roof structural members supporting formed metal roofing, the live load deflection shall not exceed l150. Shallow pitched green roof 525 the structure of a shallow pitched green roof differs slightly from the structure of a flat roof. Removing unnecessary finishes may provide sufficient capacity for a green roof of equal weight. For retrofit projects, an architect, structural engineer, or roof consultant can determine the condition of the existing building structure and what might be needed to support a green roof. Here are some easytofollow guidelines for the construction or installation of a green roof. If you are in the preconstruction stages of a building then thats the time to make structural adjustments so a green roof can be included. Vidar lerum, college of design, arizona state university lab report, april 7, 2006. Structural criteria for residential rooftop solar energy. 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. The substrate gives the right amount of nutrients to the plants so your green roof stays nice and green.

Semiintensive green roofs include features of both types. Excerpts from green roof construction and maintenance, by kelly luckett, 2009, published by mcgrawhills greensource books hi green roof fans, as one of the contributing editors here on you may know me as the green roof guy im starting a series of excerpts from my book green roof construction and maintenance. Some current buildings are not designed to withstand the additional weight load for deeper green roof systems. The designer should consult with a licensed structural engineer or architect to ensure that the building will. 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. Some roofs are finished with substantial architectural buildups such as concrete pavers or stone. Deeper green roof systems are more like rooftop gardens with six to eight inches to several feet of growing medium and a wide variety of plants.

Read this section carefully before submitting architectural, structural, plumbing, electrical, or mechanical plans for a green roof. It is important to consider the saturated weight of the roof in the design calculations. Intensive roofs are those greater than 4 inches in thickness, with some as deep as 2 feet or more, making a wide variety of plants, including bushes and even small trees, possible. The public and private benefits and costs of green roofs 4. You need to make sure that the structure can cope with. No matter what kind of green roof you are considering for an existing structure a structural assessment is necessary to be sure the roof will support the new loads. Since 2000, there has been a great emergence in green roof implementation in north america snodgrass 2006. You need to make sure that the structure can cope with the extra weight of. Table 2 is an optional table some cbos may elect to use to provide additional assurance by requiring a check of existing roof rafter spans, and supports optional criteria 1.

Green roofs are roofs that are substantially covered with living plants. A structural engineers advice is essential to ensure comprehensive design. Vegetated roofs in general are designed to have minimal maintenance requirements. It may also include additional layers such as a root barrier and drainage and irrigation systems. A green roof is a green space created by adding a growing medium and plants on. Green roof construction how to make a green roof permagard. Green roofs, also referred to as vegetated roofs, eco roofs, and roof gardens, consist of a layer of vegetation that covers an otherwise conventional flat or moderately pitched roof. Structurally, it really depends on what the green roof system entails how much soil, etc. At the present time, chicago appears to be the american leader in green roof square footage and policy. Consulting a structural engineer prior to design and installation of any type of green roof is. Facts and myths about green roofs to view more videos about green roofing, visit our youtube playlist this report was brought to you by insulation corporation of america ica a. For roof permits, also fill out the standard roof permit application pdf. As a result, a structural engineer, architect, or other qualified professional should be involved with all green roof designs to ensure that the building has enough structural capacity to support a green roof.

It is very important that you get the right people on your green roof design and make sure that the system is perfect for the structural system of your property. 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. Design method by which water is discharged from the roof when the primary roof drainage systems is not functioning or blocked. Green roof storage volume is maximized on relatively flat roofs a pitch of 1 to 2 percent.

A standard flat roof with a gradient of zero to five degrees is by default waterretaining. A green roof or living roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. Oct 28, 2016 structural considerations for green roof retrofits, technical memorandum prepared by magnusson klemencic associates, inc. Structural is widely recognized as the industry leader in repair and maintenance of civil and structural infrastructure. Chapter 16 structural design 2015 minnesota building. Live load the weight of people who will use the space, and of any mobile equipment. Intensive systems allow the designer to create a parklike setting so they are the best option for roof gardens that will be occupied. Structural engineers determine the loading requirements of a roof to resist live loads, forces such as snow, rainwater, rooftop equipment, green roofs, and maintenance crews, as well as dead loads, the basic roofing structure and materials. Biosolar green roofs where solar energy and green roofs are combined to provide renewable energy and deliver biodiversity. Construction plans for a green roof must be accompanied by maintenance and irrigation plans that include the items listed in section 4. Plant species are selected so that the roof will require minimal irrigation or fertilization vegetated after vegetation is initially established. The green roof dead load is independent of other dead loads, such as snow load, included in the guiding building code. Virginia dcr deq stormwater design specification no. In addition to city policies and mandates, the us green building councils.

Layers of a pitched green roof the structure is similar that of the flat green roofs, but here must be inserted retaining structures, which do not let the growing medium creep. Structural engineers determine the loading requirements of a roof to resist live loads, forces such as snow, rainwater, rooftop equipment, green roofs, and. You need to make sure that the structure can cope with the extra weight of your green roof, especially when saturated with water. With a green roof, the plants layer can shield off as much as 87% of solar radiation while a bare roof receives 100% direct exposure. For structural roofing and siding made of formed metal sheets, the total load deflection shall not exceed l60. These factors will guide the choices made by designersarchitects, landscape architects, or other building and design professionalsregarding the scope of a. Structural implications of green roofs, terraces, and walls. Green roofs are differentiated by the depth of the growing medium, as this directly relates to weightthe primary structural concern. The system structure for a flat, waterretaining green roof consists of a drainage layer with filterfleece, extensive roof garden.