Include
Maintenance Costs in Figuring Roof Expenses
by Tom Irvine, RRC
Generally, the less dependent a roof system is on maintenance, the
longer the roof will perform without requiring repairs or replacement.
By prolonging a roof's service life and minimizing the need for
repairs, the cost per year of roof
ownership can be substantially reduced. In the absence of regular
maintenance, this design philosophy will also postpone interior leak
development, as well as moisture infiltration into the roof system.
Design decisions should consider roof maintenance requirements at
two levels; during selection of the roof system, and when developing
the construction details for application of the roofing components.
Roof System Selection
A huge range of rooftop environments exist, each of which presents a
unique combination of criteria to be accommodated. Just a few of the
environmental items to look at when identifying future roof
maintenance considerations include:
- Building usage
- Types of rooftop equipment and associated equipment maintenance procedures
- Presence of manufacturing byproducts or debris
- Anticipated levels of foot traffic
- Presence of non-roof related construction traffic on the roof
- Planned future rooftop equipment modifications
- Type and condition of flashing substrates, adjacent walls and roof penetrations
- Proximity of the roof to overhanging trees, salt water, pollutants, etc.
- Roof drainage characteristics
- Probability of vandalism
- Other site-specific factors affecting the roof
If the roof system is custom selected to accommodate the rooftop
environment, subsequent maintenance requirements will be reduced. The
following client projects are examples of how roof system selection
and maintenance requirements go hand in hand:
| Low-rise mixed use
plaza. The client owned a five-building complex consisting of
leased offices, restaurants and shops. Tenant turnover was
fairly high, with interior renovations occurring on a regular
basis. As such, roof
penetrations often were added and removed by a wide variety of
subcontractors. All buildings had gravel surfaced built-up roof
systems. While these systems do have the advantage of being
traffic resistant, the gravel makes quality tie-ins difficult to
construct at new penetration flashings and repair areas. As a
result, the property manager was constantly chasing roof leaks,
most of which resulted from tie-in problems. In fact, the
facility's roof repair contractor had a contractural obligation
to dispatch a repair crew to the property whenever it rained. |
| Pulp and paper mill.
This client owned an older pulp and paper mill in the southern
United States. In response to
catastrophic roof leakage and an overwhelming backlog of roof
replacement work, the owner elected to install single-ply EPDM
roof systems due to the low cost and volume of work that could
be performed. This solution was in essence designed for high
maintenance. The high frequency of adjacent construction work,
debris/cleaning, foot traffic and incompatible chemical
discharge led to rapid membrane puncturing and saturation of the
roof insulation. To
avoid repeating roof replacements within four-to-eight year time
frames, extensive repairs and maintenance work had to be
completed on a regular basis. |
If each of the roof systems in these examples would have been
selected based on the key maintenance-related design criteria, leakage
and long-term expense would have been greatly reduced and potential
roof service life would have been increased.
Details for Roof System Application
Specifying an appropriate roof assembly is only the first
step in minimizing future maintenance requirements. The construction
details that govern termination of the roof membrane also have high
importance. The following examples describe detailing issues to be
considered when low maintenance is the goal.
Roof Related Sheet Metal
Sheet metal components provide the first line of defense against
water intrusion at roof perimeters and penetrations. When leakage
first occurs in a roof system, it commonly originates in either of
these two locations. Investing in a "belts and suspenders"
approach typically pays off, if the objective is long-term ownership.
Parapet walls and expansion joints can be wrapped with a single-ply
membrane prior to installing metal coping caps and expansion joint
covers. If joints in the metal open up over time, the building and
roof system will be isolated from water entry.
Flashing Terminations
The use of pitch pans should be discouraged, especially if other
flashing options are available. Pitch pans are easy to install in the
field, but need to be filled and repaired frequently. If this
maintenance is not performed judiciously, water infiltration is highly
likely. If pitch pans must be used, proper surface preparation, use of
premium sealant material, and installation of a metal cover should be
required to reduce maintenance concerns.
Where flashings are terminated with sheet metal, especially
surface-mounted counterflashings, a secondary line of defense is
worthy of consideration. This ensures that water will not leak into
the flashings should it get behind the metal. With modified bitumen
flashings, this is typically achieved by top nailing the flashings and
sealing the upper edges with roof cement and fabric. With single-ply
flashings, this may be performed by installing water cutoff sealant
behind the top of the flashing and installing a termination bar to
attach the flashing and compress the sealant. This bar is then
typically covered by the sheet metal counterflashing.
Roof Drainage
Implementing positive roof drainage through tapered
insulation or other means will reduce roof maintenance headaches.
With most types of roofs, field membrane deterioration is accelerated
where water stands on the surface. If water does not pond, associated
maintenance requirements should be reduced. The absence of ponding
water will minimize the amount of debris that collects on the roof,
such as waterlogged tree litter.
Interior gutters between sloped roof systems should be avoided, if
any other design options are available. Interior gutters are notorious
for leaking, and represent a maintenance person's nightmare. If
interior gutters must be used, a "belts and suspenders"
approach is nearly always warranted.
Many other opportunities exist to implement low maintenance roof
systems and detail design that are beyond the limits of this article.
The point to keep in mind is that maintenance requirements and roof
ownership costs can be reduced if key decisions are well thought out
prior to installation of a roof system.
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