Architects and Roof System Designers: Your Details and Drawings Are Seriously Lacking Design Intent

K. I’VE WITNESSED OWNERS WHO HAVE HIRED PROFESSIONALS TO DESIGN BUILDINGS COSTING HUNDREDS OF MILLIONS OF DOLLARS, AND YET THESE “PROFESSIONALS” OFTEN DO NOT EXHIBIT THE STANDARD OF CARE EXPECTED.
I would say and have testified that the design standard of care is to properly communicate to the roofing contractors the design intent—to all conditions. As the designer, it is required you design all the architectural, mechanical, plumbing, etc., conditions to the roof system design (refer to recommendation “I”) and detail them appropriately. Manufacturer, NRCA, WSRCA details should never, ever be part of the construction documents. They are guides with which to develop project-specific details.

COMMUNICATE A BETTER DESIGN INTENT

Although these are certainly not the only items of concern, if you can ad- dress them you will start to communicate a better design intent and convey to the roofing contractor that you are knowledgeable about this important building envelope system and that the contractor should bid it as designed. Doing this also will help me save face.

Thank You.

An Actual—and Poor—Scope of Work

The following actually was issued by an architect:

    1. Provide all material, equipment and labor to furnish and install a new single ply roof membrane system (Roof Recover) over the existing built-up roof (BUR) assembly at the one story retail business. Total roof area is approx. 30,343 6. sf. Total tenant leasable area is approx. 29,417 sf.

    2. As part of the work, remove all existing ballast, investigate the existing membrane and make any repairs to the existing membrane to ensure that it is watertight. Provide and identify the allowance for watertight repairs in your proposal.

    3. Satisfy all Energy Code requirements including the applicable International Energy Conservation Code (IECC) code requirements.

    4. Furnish and pay for all permits required for this work.

    5. Applicator shall have applied accepted roofing system on two or more projects, similar size or larger, which have performed satisfactorily for at least ten (10) years.

    6. The new roof membrane shall be a 60 mil single ply membrane—provide pricing for an EPDM, PVC and TPO roof system. Include the warranty provisions for each roof membrane. PVC and TPO roofs to be a white color. The EPDM roof can be black but should be coated in a light re ective coating to satisfy the code required reflectivity requirements.

    7. Apply roofing system (cover board, roofing membrane and flashings) in strict accordance with approved manufacturer’s written specifications.

    8. Furnish and install a roof recover insulation board over the existing membrane, mechanically fastened to the existing roof deck.

    9. Remove and replace all prefinished metal copings at the roof perimeter. New copings shall be finished brown to match the existing copings. Coating to be a high performance coating such as Kynar. Sheet metal shall be installed with concealed fasteners or where not practical with non-corrosive screw fasteners with neoprene washers for a watertight condition.

    10. Curbs of existing Roof Top Units, Exhaust Fans and Roof Hatches shall be reflashed and made weather tight.

    11. Furnish and install new vent flashings for all plumbing and other types of vent stacks.

    12. Furnish and install new flashings and watertight detailing for the pedestal mounts of the existing sign.

Illustrations: courtesy of Hutchinson Design Group Ltd.

Pages: 1 2 3 4

About Thomas W. Hutchinson, AIA, FRCI, RRC, CSI, RRP

Thomas W. Hutchinson, AIA,FRCI, RRC, is principal of Hutchinson Design Group Ltd., Barrington, Ill., and a member of Roofing’s editorial advisory board.

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