Both BUR and MBR membranes are relatively fragile components. The membrane is subjected to wind, hail, snow, rain, and ultraviolet
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CHAPTER FIVEBuilt-up roofing membrane Glass ply premier
or glass ply IV
Cant 8" min. to
24" max.
2"
Bestile Concrete
primer
Bestile
F I G U R E 5 - 1 5 Flashing design.
Felt strip over nail heads and top of base flashing with glastite flexible set in bestile
Elastomeric sealant
Draw band to weld umbrella to back
Provide for removable counterflashing
Fasteners approx. 24" on center Asphalt
B
F I G U R E 5 - 1 6 (A) Expansion joint cover. (B) Stack flashing. (C) Equipment or sign sup-port. (D) One-way roof vents.
Flexible vapor retarder to serve as insulation retainer attached to top of both curbs and extended over base flashing as a counterflashing
Curb form expand-o-flash
Fasten approx.
8" on center with screws or EOF nails Fasteners approx. 8" on center
Chamfer top of wooden curb each side to drain
energy, as well as foot traffic and various forms of abuse. While other parts of the building are more visible, and thus tend to be maintained on a regular basis, the roofing system often is overlooked until it leaks.
By that time, extensive and costly damage may already have occurred.
Inspections, maintenance, and repair are an excellent opportunity for securing an ancillary cash flow. This should be treated as a separate business. If it is well managed, it can be a simple cash cow that also mar-kets your company’s other services.
The most important reason to establish a program of periodic maintenance inspection is to protect the owner’s investment. A prop-erly executed maintenance program can add years to the life of a roof. It can also detect minor problems before damage is widespread, which in turn avoids interruption of the internal functions of the building. Because of this, more and more building owners and man-agement firms are hiring qualified roofers to inspect their roofs twice a year. During such an inspection, carefully check every component
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CHAPTER FIVESet bolts in elastomeric sealant
14" min. to bottom of equipment
Fasteners approx. 24" on center or as required
Mopping asphalt Glastite
flexible flashing
Nail flashing approx.
8" on center with approved fasteners
Industrial roof cement
C F I G U R E 5 - 1 6 (Continued)
of the roofing system for signs of deterioration. The following are some of the most common problems encountered on roofs.
Blisters
Blisters are usually associated with skips or voids between two imper-meable surfaces. The entrapped air contains moisture, which expands as the temperature rises and creates sufficient pressure to push the felts apart. Small, unbroken blisters that are less than 12 inches in diameter are best left alone. Blisters holding pressure do not leak water. If the felts are organic, recoat the bare spots over unbroken blis-ters with industrial roofing cement to protect against deterioration.
Repair large or numerous blisters with hot asphalt.
Flange set in industrial roofing cement Manville FP-10 one-way roof vent
Loose insulation
Open Closed
Insulation Deck
Felts set in industrial roofing cement or hot asphalt
D F I G U R E 5 - 1 6 (Continued)
Repair broken blisters using the following steps.
■ Remove the entire blister to the point at the edge where remain-ing felts are well adhered.
■ Let the remaining surfaces dry thoroughly.
■ Fill the depression level with the surface of the BUR using roof-ing cement.
■ Trowel the cement smoothly over the depression patch and feather the edges so that water flows easily over the patch.
Ridging
This problem is sometimes called buckling or wrinkling and is the result of dimensional changes in the BUR membrane. Some of the common causes of ridges follow.
■ Interior moisture vapor migrates to the cool underside of the membrane, condenses, and then is absorbed by the organic fibers of the felt, causing a swell or ridge over each joint of insu-lation in a picture-frame pattern.
■ An unattached or poorly attached membrane or insulation shifts during seasonal changes due to expansion and contraction.
■ Insecurely attached deck units shift out of position.
■ Slippage of the membrane.
Ridges flex during seasonal changes or with structural movement.
This can cause them to fatigue and crack on or near the crown. Recoat unbroken ridges in organic felt membranes wherever the coating has slipped and left bare felt.
Splitting
This can be due to damage during or after construction or to condi-tions that cause a concentrated stress in the BUR membrane. Possible causes include stress from differential movement or cracking of the supporting structural deck or substrate, which can occur where the deck changes direction, where two types of deck are installed adjacent to each other, or where a BUR is solidly cemented to a deck that devel-ops shrinkage cracks.
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CHAPTER FIVEStress from the contraction of the membrane in an area where the membrane or a component of the roofing system is poorly attached can also cause splitting. This stress can occur between the deck and insulation, the layers of insulation, or the BUR membrane and insu-lation.
Another common cause of splitting is breakage of the attachment between components by rolling loads across the roof, heavy loads that cause deflection, or the drumming of the roofing system by high winds. Membrane splits will recur as long as the basic substrate stress is not accommodated. For a long-term solution, proceed as follows.
1. Clean the surface of the membrane a minimum of 16 inches beyond the split edges. Completely remove the aggregate surface if present.
2. Prime the cleaned surface if it is dirty or contaminated.
3. Position dry, unattached 4-inch-wide felt centered over the split.
4. Cover and seal the split. Do not re-embed the aggregate so that the repair can be monitored.
To provide some flexibility to a split repair with considerable movement, follow the first three steps above, and then:
1. Over a 4-inch strip, cement a 16-inch-wide strip of elastomeric film embedded in a 1⁄8-inch troweling of cement.
2. Strip the edges of the elastomeric film with a 6- and 10-inch strip of inorganic felt, each embedded and coated in a 1⁄8-inch troweling of roof cement or hot asphalt, as illustrated in Fig.
5-17.