New construction roofing and waterproofing
generally presents an application environment very different
from a reroofing project.
The NRCA publication "HARK"
— The Handbook of Accepted Roofing Knowledge" presents
a wealth of information and guidelines applicable to successful
completion of new construction roofing work.
It is a very common problem for
General Contractors to direct roofing or waterproofing contractors
to install moisture protection prematurely or to "phase"
the installation with the G.C’s objective, to allow interior
trades to proceed, being the primary concern. This often results
in a substandard roofing installation.
Another common problem, especially
on large projects, is damage to the moisture protection system
by construction traffic of other trades.
These are avoidable problems if
properly addressed. The best approach is to conduct a pre-installation
meeting attended by all interested parties, i.e., owner's representive,
G.C, Architect, plumber, electrician, roofing materials manufacturer
and the roofing contractor. The NRCA pre-roofing conference
checklist includes:
- Establish trade-related job
schedules, and appropriate trade sequencing, including timely
installation of any rooftop mechanical equipment, to avoid
or limit traffic on the roof.
- Establish construction schedules
and work methods that will prevent roof damage; these may
include provisions for installation of a temporary roof, for
installation of traffic paths or walkways for protection of
finished roof systems, and for the use of mechanized roof
application equipment.
- Establish the conditions under
which a temporary roof or traffic paths will be used, and
who will pay for them.
- Require that all walls, curbs,
drains, and other penetrations be in place prior to installing
the roof system.
- Establish those areas on the
job site that will be designated as access, staging, work,
and storage areas.
- Establish weather conditions
and working temperature criteria to which all parties must
agree.
- Establish provisions for on-site
monitoring after the roof application is completed to assure
that the finished roof is not damaged by other trades. Establish
provisions for payment for repairs in the event that damage
does occur.
- Establish and review all related
EPA and OSHA regulations and other safety requirements, including
considerations for safety of building occupants.
- The pre-installation inspection
should include surface inspection of the structural deck.
If changes to the agreed upon
conditions are desired, the party requesting the change should:
- Give written notice of the
desired changes to all parties.
- Secure written agreement to
the changes from the project designer and all other parties
affected by the change.
Preinstallation Deck
Inspections
Metal Deck:
The inspection team should walk
all deck surfaces and observe the general installation, checking
that the:
- Metal deck is properly aligned
- Roof openings are properly
reinforced
- Deck appears to be properly
secured with fastners or welds
- Drains are properly installed
and clamped at correct elevations
- Deck is proper spaced at walls
and expansion joints
- Deck is not damaged or deformed
For further
information please consult Steel Deck Institute
Concrete Deck:
- The deck should have a wood-trowel
medium smooth surface finish, without significant depressions
or surface irregularities, such as fins or ridges. Consult
American Concrete Institute Section 301 — 11.7.3 for
precise specification.
- The deck must be properly cured
with moisture content andhave a dry surface. The concrete
deck surface must be free of any laitance, oils, dust, dirt,
frost, unapproved curing compounds or other foreign matter
detrimental to the adhesion or performance of the membrane.
Moisture content tests are required
following ASTM D-4263 procedures (plastic film test).
Recommended deck curing time of
28 days is somewhat arbitrary but should be used as a guideline.
Do not use any curing agents, which are not approved, in writing,
from the curing agent manufacturer and from Barrett. A burlap
wet cure is highly recommended as the preferred method of curing
concrete. The concrete deck surface must be free of any laitance,
oils, dust, dirt, frost, unapproved curing compounds or other
foreign matter detrimental to the adhesion or performance of
the membrane. The General Contractor shall certify no unapproved
curing compounds have been used.
For further
information consult ACI@.
Wood plank
and Plywood Decks
Wood decks must be stable,
well seasoned or Kiln-dried solid sawn lumber. Plywood should
meet American Plywood Association (APA) standard APA PRP-108,
C-DX exterior grade. Wood plank should be a minimum of one inch
thick, or greater, consistent with support spacing; plywood
should be a minimum of 1/2" inch thick, consistent with
support spacing.
Prior to installing rosin
paper and mechanically fastened a base sheet or insulation,
inspect surface and edge conditions for proper fastening and
tight joints.
For further
information consult American Plywood Association or NRCA
For specific information on:
Tectum — Cementitious
Wood Fiber Decks
Lightweight Insulating Concrete
Decks
Gypsum, poured decks
Gypsum panel decks
Thermosetting Insulating Fills
Please
contact Barrett Technical Services
The keys to successful moisture
protection are quiet simple:
- Proper Design
- Quality Materials
- Quality Workmanship
- Regular Inspections and timely
Maintenance
Barrett
offers
- Design assistance
to Architects
- Highest
quality materials
- Approved
contractor network
- Inspecton
services
- Maintenance
programs
- Long term
warranties
