We asked contractors, consultants and suppliers from across the country to provide us with their best advice regarding commercial rooftop accessories. Here we present the consensus recommendations.
It’s interesting to note that during our discussions, a phrase that came up with remarkable frequency was, “I know this probably seems basic, but you’d be surprised how many times I’ve seen ….” Make sure your crews don’t fall into bad habits, and that they understand the importance of these critical components of the roofing systems they install.
The compendium of advice, tips, admonitions, recommendations, guidance, exhortations, appeals, cautions, entreaties and counsel:
- Carefully examine the condition of the existing roof drains. Existing drains may be made suitable for re-use by repairing/replacing broken components. If existing drains are not suitable for re-use, install new drains compatible with the new roof system.
- Select the correct roof drain style, i.e. retrofit or new drain unit.
- Confirm that there has been adequate drainage of the roof in the past and that the use of retrofit drains will not diminish overall drainage capacity.
- Consider adding an additional drain to facilitate drainage of the roof surface. Provide at least one overflow drain or overflow scupper for each primary drain unit — plumbed into a separate independent line for unrestricted drainage.
- Retrofit drains must feature anti-back-up protection to prevent water from getting under the new membrane in the event of a plugged sewer or backed-up drainpipe.
- Use a drain with a separate clamp ring to secure the drain body to the roof membrane.
- Use metal strainer domes that bolt down if potential vandalism is anticipated.
- Ensure that there will be a program of regular roof maintenance by the building owner for the purpose of monitoring the roof condition and function of the roof drains.
- Specify/install underdeck clamps to stabilize roof drain bases at the roof deck.
- Color choice, finish type (Kynar, polyester, etc.) and thickness can have a significant impact on your costs if quoted incorrectly. Read the metal finish specifications carefully.
- Check the specifications for performance requirements such as FM Global Approvals, ASTM or ANSI/SPRI test methods. The International Code Council has adopted the ANSI/SPRI test protocols for the latest version of the International Building Code.
- Carefully field-check the project comparing the design drawings to actual field dimensions to ensure proper fit and coverage of the perimeter edge metal.
- Make templates of radius walls or other unusual conditions.
- Get the paperwork finished early (signed purchase order, bond info, shop drawings or other submittals). This can help avoid delays when the material is needed.
- Corrosion can be reduced or eliminated by keeping in mind the galvanic scale when selecting materials and fasteners used for attachment.
- The joint must be of sufficient size to provide the proper range of movement for a maximum condition, not the condition at the time of installation. Joint cover selection should be made based on engineering analysis.
- There needs to be full coordination of all exterior closure systems (including walls) in order to provide a weather-tight system.
- Compatible mounting conditions are important. What are the substrates or other items of contact? Are the mounting areas wide enough for correct flashing? Determine the orientations of the elements to properly address clearances and exposures.
- The compatibility of fire barriers beneath a given joint may be critical to maintaining the rating of the products and the construction. The sequence of installation for these products also is critical as in many cases, more than one trade is involved.
- Any time there is a material in the expansion opening, there must be enough additional room provided for the material to still function at the maximum closure movement. There also should be enough material to fill the joint at maximum normal opening movement.
- The use of traditional metal pitch pans in new roofing systems has significantly decreased in recent years as improved methods of flashing penetrations have been developed.
- In place of traditional metal pitch pans, use of modern curing pourable sealer materials allows for improved performance when flashing difficult penetrations.
- Pitch pans require frequent inspection and maintenance.
- Non-shrink grouts, improved pourable sealers and rain collars can enhance pitch pan performance.
- Minimum height should be four inches above the roof surface.
- Use 3- to 4-inch base flange with full corners and no open seams.
- Solvent wipe and prime interior walls on all metal units.
- Top off the pan with enough material that it slopes away from projections, allowing positive drainage.
- Aluminized mastic will retard the aging of the asphalt and decrease thermal movement.
- Sometimes you can install a skirt or cone around the penetration to protect the pitch pan.
- Metal covers/closures may be used to cover pitch pans — allowing horizontal penetration of pipes/conduits/lines.
- Designs should be project-specific to the type of roof membrane installed, as well as accounting for level and slope changes.
- For walkways to be effective, they must be placed where people walk, and people will walk the shortest distance, not necessarily the route that looks best on the roof from an aerial view.
- Elevated walkways encourage workers to use the walkways.
- Walkways should not restrict drainage.
- Walkways should be easily adaptable to changing traffic patterns as new rooftop equipment is added or relocated.
- Walkways should be slip-resistant.
- Walkways should be able to protect the membrane over the membrane’s lifetime; if not properly selected and installed, they can cause more problems than they solve.
- Walkway materials should be sufficiently rigid to distribute imposed loads on the roof system to minimize insulation and roof membrane damage.