(Elastomeric and Thermoplastic)
There are numerous single ply systems on the market and selection of the best product for your installation is dictated by building height, wind exposure, foot traffic, fire rating, attachment method, selection of contractor, and cost. I strongly suggest architects and specifiers review design tools and standards promulgated by the Single Ply Roofing Industry association prior to selection.
First, your selected manufacturer should be reputable and known in the industry. They should be in existence for as long as the desired warranty - likely, twenty years.
Should you base your design on a particular manufacturer, use their typical details. Do not deviate without their written approval. By copying their details, you are doing your professional best to ensure the system is designed correctly and that manufacturer will provide a warranty. Use of their nomenclature is not required - generic is fine. Your drawings should include all special conditions and without exception the membrane should always turn 8" up the vertical surface. Do not accept less without written acceptance from the manufacturer that this will not in any way affect the warranty.
Drawings should reflect all major components shown in the specifications. Basically, as details are sections, show all items that can occupy space in the section. Fasteners and adhesives can be left to the specifications. Consider using axonometric details to show complicated details or how components might need to be installed. This will clarify difficult or unusual conditions for your contractor. Ensure all metal flashing or flashing components are coordinated with that section of the specifications.
Your contractor should not have to guess as to your intent or need to read your mind. I strongly suggest you do a mental walk around the perimeter of your roof and around all equipment and penetrations of the roof membrane. If there is any doubt whether a detail will convey the correct concept and amount of information to your contractor, draw the detail. This can be time-consuming but, so can litigation and additional time and effort resolving conflicts in the field and placating angry clients.
If a detail is not shown in a manufacturers detail book or online, draw the detail and send it to the manufacturer or their representative for review. If your selected manufacturer will not come by your office to review your documents or do so by correspondence, I suggest you discuss your project with another manufacturer.
Be sure to draw all of the components of the roofing system. On buildings with metal decks both insulation and/or substrate boards are often used and need to be shown in their correct thicknesses.
Insulation is a critical component of each roofing system. The specified insulation type must be compatible with the roofing system and roof construction. Verify that the correct insulation thickness is shown at building perimeters where the roof system terminates. In systems utilizing tapered insulation or crickets, this thickness will provide a higher finish elevation that must be coordinated with parapet height or architectural features at the back of parapets. I have seen less than 42" parapet height occur far too often. To simplify design you might consider a standard flashing height with an elevation of 8" above the high point of the roof.
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