The construction documents describe the roof at a level of detail that should be installable as drawn. In practice, the field often reveals conditions the drawings did not anticipate. The disconnect between the spec sheet and the field is a normal part of construction; how it is handled distinguishes a good project from a problematic one.
Here are the three most common patterns we see.
Pattern 1: The drawing shows a generic detail; the field is specific
A wall-to-roof transition drawn on the construction documents shows a standard step-flashing detail. The field condition is a wall that turns at 67 degrees rather than the 90-degree assumption, with a soffit return that the drawing did not show.
The honest answer is that the drawing's generic detail was a placeholder for the typical case; the field requires a custom detail that the drawing does not specify.
How we address it: We field-detail the transition with a hand-formed piece, document the as-built condition with photographs and a sketch, and send the documentation to the architect within 24 hours of installation. The architect adds the field-detail to the architectural file for future reference.
This is not a change order; it is field detailing within the spec's intent. The architect should not be billed for the resolution; the contractor should not pretend the drawing is sufficient when it is not.
Pattern 2: The drawing specifies a material; the manufacturer has changed
The drawing specifies a particular underlayment product that the architect found on the manufacturer's spec sheet during design. By the time the project reaches construction, the manufacturer has discontinued that product or modified its specifications.
How we address it: We identify the substitution requirement before ordering, propose an equivalent product with current FPA/NOA, and seek architectural approval in writing before substituting. The substitution is documented in the contract change-order log.
If the substitute has slightly different physical characteristics (slightly different thickness, slightly different color), we communicate the differences explicitly. The architect may approve, request a different substitute, or pause for review.
Pattern 3: The drawing's pitch is below the material's minimum
A roof drawn with a 3:12 pitch but specifying clay tile (whose minimum pitch is 4:12 for standard installation). The pitch and material are incompatible per the manufacturer's specifications.
How we address it: We flag the incompatibility at construction documents review, before any work begins. The options are typically:
- Raise the pitch through framing modification (architect's decision)
- Substitute a material approved at the actual pitch (typically metal)
- Use the specified material with an upgraded underlayment system that the manufacturer approves for the lower pitch
The decision is the architect's, but we raise it as soon as we see it.
What we will not do
Three things:
1. Build a known incompatibility
If the drawing specifies a roof that we know will fail (incompatible pitch, missing product approvals, structural conflicts), we do not build it. The conversation about the change is with the architect and the owner, before construction proceeds.
2. Substitute materials without architectural approval
Even when we are field-substituting an equivalent product, the substitution is approved in writing. We do not assume that "equivalent" is the architect's preference.
3. Field-detail without documenting
Any field detail that differs from the drawings is photographed, sketched, and documented in the closeout package. The architect and the owner have the as-built record.
What architects should ask for
Three things in the closeout package:
- As-built deviations from the construction documents, with photographs and field sketches.
- All substitution approvals documented in writing, with reasons.
- The final product list with current FPA/NOA references.
Together, these document the actual roof as installed. The construction documents become the design intent; the closeout package becomes the truth.
A note on the relationship
The architect and the roofer working productively is the result of mutual respect for the other's competence. The architect knows architecture; the roofer knows roofs. Neither should pretend to know the other's domain better than the specialist.
The best projects we have completed had architects who treated us as the technical authority on roofing and asked our judgment on questions where ours mattered. The least productive projects had architects who specified roof details against current code or against manufacturer requirements and then resisted the field correction.
The construction documents are the starting point. The field is the reality. The honest reconciliation between the two is the work.
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