حوزه فعالیت در سقف شیبدار
For most projects, periodic observation by the roofing designer is sufficient. But for others, full-time observation by the designer or a roof consultant is prudent. The purpose of the observation is to help ensure that the work is being executed in accordance with the contract documents.
The amount of observation will depend upon:
- Desired system reliability: If a highly reliable roof is desired, it should receive more field observation.
- Characteristics of the roofing system: Some systems are more demanding, or less forgiving, than other systems with respect to workmanship and weather conditions at time of application. Even if a knowledgeable and conscientious contractor is performing the work, demanding systems present challenges. They should therefore receive greater observation in order to help avoid inadvertent mistakes. An example where increased observation is helpful is when a modified bitumen membrane is applied in cold adhesive when the ambient temperature is near the lower boundary recommended by the manufacturer. Increased observation could prevent the application from occurring if the temperature drops below the minimum recommended temperature.
- Cost: As the cost of the roofing work increases, the amount of observation should also increase.
- Complexity: Complex or unique roofs (such as unusually shaped roofs) or those with an unusually large number of penetrations should receive greater observation.
It is imperative that the observer understands thoroughly the system being installed. The observer should:
- Be provided with portions of the contract documents related to the roof.
- Be provided with a copy of the approved submittals.
- Be provided with copies of all changes related to the roof.
- Attend the pre-roofing conferences.
- Verify that the materials on-site are those identified in the approved submittals and that the materials have FMG or UL labels when so specified.
- If a BUR, modified bitumen, EPDM, or sprayed polyurethane foam system is specified, follow the quality control guidelines co-produced by NRCA.
- If fastener pullout tests were specified, verify that the results are acceptable. If the values are lower than anticipated, the roof membrane manufacturer should provide the contractor with a revised fastening pattern that is commensurate with the test results.
- If it appears that wheel loads or stored material loads exceed the specified load limits, the contractor should be advised immediately.
- Bring to the immediate attention of the contractor’s job-site person (who was identified during the pre-roofing conference) any need for a change in the contractor’s work practices or a need for corrective work.
- As with submittal approval, be cautious in approving materials, systems and details that are not in accordance with the contract documents while performing field observations (Figure 16). For example, the roofing crew may desire to use different fasteners to attach the membrane because the approved fasteners were not sent to the job site. Before accepting the fasteners, determine if wind uplift test ratings will be affected and if the membrane manufacturer will approve the alternative fasteners. Another example is a penetration detail that the foreman desires to flash differently than detailed. Is the change proposed in order to provide a better detail, or is it being proposed because it is simpler and cheaper to install? If the proposed detail is not as conservative as the original detail, it should probably not be approved. Requests to use alternate details of materials should be referred to the Designer of Record for written approval.
Write daily reports and give them expeditiously to the contractor (and to the roofing designer if the observer is not an employee of the structural firm that designed the roof). Report copies should be included in the file prepared for the Owner, as discussed in section 4.4.5.