#2: Construction Roof Traffic
In order to maintain the required hourly fire resistance rating of a roof assembly, the bond of the spray-applied fire resistive material (SFRM) must not be weakened during or after application. Unfortunately, there are too many cases where this does occur. By far, the predominant reason for delamination of spray-applied fire resistive materials is Construction Roof Traffic, typically resulting from condensed or out of sequence work schedules.
"Construction Roof Traffic" refers to the activity of walking, installing or working with equipment on the roof of a building. Roof traffic above areas where the SFRM has already been applied, especially to steel roof deck, is a major concern for SFRM manufacturers and building team members. The adhesion between the material and substrate is often compromised by impact forces and deflection, which cause the SFRM to fall off or "bridge".
Bridged material refers to material essentially separated from the substrate but held in place cohesively by adjacent material. Bridged SFRM may fall off weeks, months or even years after the initial damage, resulting in an unsafe condition. SFRM delamination or bridging not only jeopardizes the hourly fire resistance ratings required to meet governing building codes, but can also delay the construction work schedule, increase overall costs and present a hazard to building occupants.
As a global manufacturer with years of experience in SFRMs, ISOLATEK INTERNATIONAL recognizes this industry concern and offers several precautionary measures to help prevent SFRM delamination and the resulting consequences. Using terminology similar to that used by others in the fire protection industry, we clearly state on the back page of our product brochures under Section 3.2.5 of the Guide Specification: "The application of sprayed fire protection to the underside of roof deck shall not commence until the roofing is completely installed and tight, all penthouses are complete, all mechanical units have been placed, and after construction roof traffic has ceased". Therefore, all roof work, including work on the perimeter and installation of the roofing membrane, should be completed prior to the SFRM application. In addition to proper sequencing and coordination between trades, the following additional guidelines will help minimize the problem:
- The design specifications for roof deck gauge and spans should be in accordance with the Steel Deck Institute recommendations for construction and maintenance loading.
- Roof assemblies consisting of gypsum wallboard and insulation (polyisocyanurate, polystyrene, mineral fiberboard, etc.) above the metal deck is preferred instead of insulation only. The layer of wall-board (5/8") provides a more rigid roof system and helps distribute loads more effectively.
- The SFRM manufacturer's recommended adhesive or bonding agent should be applied to all steel roof decking (without concrete topping) prior to the application of the SFRM. Bonding agents enhance the ability of the SFRM to adhere to the substrate.
- When roof traffic is anticipated, as in the case of periodic maintenance,
roofing pavers should be installed as a walkway to distribute loads.
- Although several painted roof decks are classified in certain UL roof designs, galvanized roof deck is a better substrate for bonding of SFRMs. Painted roof decks increase the risk of delaminations.
Following these key guidelines will help minimize the problems associated with fireproofing delamination due to construction roof traffic. However, proper construction scheduling and coordination between trades cannot be overemphasized.
