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What do you do when the roof plan and the details conflict on a bid set?

By The Sharp Pencil team

Do not pick the cheaper one. Do not average the two. First, check the order of precedence clause in the agreement and Division 01 for that job. Then send a written RFI. Name both sheet and detail numbers. State the quantity and price effect. Ask which requirement governs. If no answer arrives before bid day, price the requirement your contract tells you governs. Where the documents give no ranking, consider carrying the more complete scope that satisfies both requirements when the two can be built together, and state that assumption in writing where the bid rules allow it. If the two requirements cannot both be built, get a decision from whoever owns the bid before you submit.

That order matters. Bury a conflict in your own notes and it costs you money after award. Raise it in writing before bid day and it becomes a clarification everyone bids on.

Which document governs when a roof plan and a detail disagree?

The job's own contract governs first. There is no single rule that fits every bid set.

Some contracts rank the documents. Federal construction wording in FAR 52.236-21, for example, says the specifications govern if drawings and specifications differ. A separate GSA supplement, GSAR 552.236-21, adds that larger scale drawings govern smaller scale drawings, where that supplement is part of the contract. Many private contracts use the AIA approach instead. AIA A201-2017, Section 1.2.1, treats the contract documents as complementary and says what is required by one document is binding as if required by all of them. That wording does not let an estimator delete a detail requirement just because the plan shows something simpler.

Read the precedence clause before you decide any of these common fights:

• The roof plan assembly lists membrane and insulation. A large scale assembly detail adds a cover board.
• The plan schedule lists one membrane thickness. A flashing detail or specification section lists another.
• A roof plan note gives one base flashing height. A parapet detail dimensions a taller flashing.
• The roof plan and a plumbing or mechanical sheet show different drain or curb counts.
• A field fastening pattern on the plan differs from the perimeter and corner pattern in a detail or specification.

A detail is often more specific than a small scale plan, and many contracts do say larger scale work governs smaller scale work. Treat that as a clause to find in your documents, not as a habit to apply to every job. If the clause is not there, specificity alone does not settle price, scope, or warranty risk.

What should you check before you send the RFI?

Work through the set in this order so the RFI is complete the first time.

1. Confirm that it is a real conflict. Check addenda, revised sheets, schedules, and the specification section for the same assembly. Two documents that can both be satisfied are not in conflict. If one adds a layer and the other is silent, you may simply have an incomplete plan assembly.
2. Find the precedence clause. Look in the agreement, the general conditions, and Division 01. Write down the exact ranking, if any, in your bid notes.
3. Quantify both versions. Price the difference, not just the headline item. A cover board changes board count and can change fastener length. A taller base flashing changes vertical membrane area and termination work.
4. Check who else is affected. Drain and curb conflicts can sit on plumbing, mechanical, structural, and elevation sheets, not only on the roof plan. That cross sheet check is why our page on the roofing RFI register treats open drawing questions as bid items, not as paperwork.
5. Send the RFI before the question deadline. A perfect question sent after the deadline often gets no answer that helps your bid.

Keep both quantity sets visible in your takeoff workbook until the answer arrives. If you overwrite the first version, you lose the ability to show what changed when an addendum lands.

How do you write an RFI that gets a usable answer?

Name the exact documents, quote the conflict in short form, and propose a resolution. Vague questions get vague answers.

A usable RFI for a roofing conflict includes:

• Project name and the RFI subject in one line.
• Roof plan sheet number and the assembly, note, or schedule that conflicts.
• Detail sheet and detail number, or specification section and paragraph, that says something different.
• One sentence on each requirement, with dimensions or thicknesses stated.
• The quantity or price effect, if you know it, stated as a difference between the two versions.
• Your proposed resolution and the date you need the answer by to hold your bid price.
• A direct question: which requirement should all bidders price?

Example wording, with the names left generic: Roof plan R-101 lists the field assembly as membrane over insulation with no cover board. Detail 5 on A-501 shows a cover board over the full roof field. Please confirm whether the cover board is required over the full field, only at the locations detailed, or not required. The added layer changes the material list for the full roof area.

That wording does three jobs. It proves you read both documents. It tells the design team the bid effect without arguing. And it gives them a choice they can answer in one sentence or by addendum. For more on logging and closing questions like this, see the roofing RFI register.

Worked example: a cover board in the detail, not on the plan

This is a hypothetical example, not a real job.

Say the roof field is 200 feet by 120 feet. The roof plan assembly lists single-ply membrane over two layers of insulation, with no cover board. A large scale assembly detail shows a cover board between the top insulation layer and the membrane, drawn across the full roof field. The specification section for the membrane system also lists a cover board as part of the assembly.

Step 1, roof field area:
200 ft x 120 ft = 24,000 SF

Step 2, net cover board count if the boards in this hypothetical are 4 feet by 8 feet:
4 ft x 8 ft = 32 SF per board
24,000 SF / 32 SF per board = 750 boards net

Step 3, order quantity with a 5 percent cutting and waste allowance for this rectangular field:
750 boards x 1.05 = 787.5 boards, rounded up to 788 boards

Step 4, state the bid effect plainly:
The conflict is not a rounding question. It is 788 boards of material, plus any change in fastener length or adhesive quantity the added thickness causes, plus handling. If the plan version is priced and the detail version is enforced after award, that full amount comes out of margin. If the detail version is priced, the RFI is answered by addendum, and every bidder removes it, you can deduct a clean, separate quantity set.

The math does not decide which document governs. Only the contract language and the design team's written answer do that. What the math does is make the question worth asking early, while there is still time to reprice. Our guide to how to price a TPO roof covers the related lines that move when an assembly layer changes.

Keep the cover board as a separate line in your internal bid notes until the conflict closes. Then, if an addendum removes it, the deduct is arithmetic. If no answer arrives, you already know the cost of carrying it.

What do you price if no answer arrives before bid day?

Use this order, and write down which step you stopped at.

1. Follow the precedence clause if the job has one. If it says specifications govern drawings, or large scale governs small scale, price that requirement and cite the clause in your internal notes.
2. If the documents are complementary with no ranking, consider carrying the scope that satisfies both requirements where the two can be built together. In the worked example, that means carrying the cover board, because a roof built with it satisfies the detail and the specification, while a roof built without it satisfies only the plan. Carrying the greater scope protects margin after award but can make the bid high, so confirm that trade-off with whoever owns the bid.
3. State the assumption where the bid rules allow a qualification or clarification. Name the sheet and detail you priced. Keep the wording short and factual.
4. On a hard bid where a qualification could make the bid non-responsive, especially on a public hard bid, do not attach conditions on instinct. Raise that choice with whoever owns the bid decision before submission. The safe estimating choice and the safe bidding choice are not always the same sentence on the form.
5. Keep the delta priced separately in your own file. If you win and the design team later chooses the lesser scope, you can offer a clean deduct. If they choose the greater scope, you are already covered and can show the pre-bid RFI.

What not to do matters just as much. Do not split the difference. Do not price the plan and hope the detail is a leftover. Do not bury a silent allowance with no sheet reference. No one will find it or defend it later. And do not treat a verbal answer at a pre-bid meeting as closed until it shows up in meeting minutes or an addendum.

Which conflicts are worth stopping the bid for?

Stop and ask on any conflict that changes one of these:

• Assembly layers: a cover board, a second insulation layer, a vapor retarder, or a different deck preparation.
• Membrane facts: thickness, attachment method, or seam and flashing requirements.
• Heights and lengths: base flashing height, parapet wrap, curb flashing, or edge metal profile.
• Counts: drains, scuppers, curbs, hatches, walkway pads, or penetrations shown differently on another sheet.
• Fastening: field, perimeter, and corner patterns, or adhesive rates that differ between the plan, a detail, and the specification.

Small wording differences that do not change quantity, attachment, or warranty eligibility can go in bid notes. Anything that moves material, labor, or system eligibility goes out as a question. If the answer affects which system you can warrant, say so in the RFI. That is a scope question, not a complaint.

FAQ

Does the detail always govern over the roof plan?

No. A detail often shows the more specific condition, and some contracts say larger scale drawings govern smaller scale drawings. Other contracts rank specifications above drawings, and AIA style documents treat the set as complementary with no simple plan versus detail winner. Read the precedence clause for that job first.

Does the specification always govern over the drawings?

No. Federal wording in FAR 52.236-21 does rank specifications above drawings, but that clause applies where it is part of the contract. A private bid set may rank documents differently or give no ranking at all. Do not import a rule from another job.

Should I price both versions of a conflict?

Price both versions in your own working file so you know the delta, then submit one bid number based on the governing document or on a stated assumption. Separate internal quantity sets let you adjust fast if an addendum answers the question.

What if the conflict is found after the RFI deadline?

Send the question anyway, keep a record that you sent it, and price using the contract precedence clause, or, where there is no ranking, the scope that satisfies both requirements if the two can be built together. State the assumption only where the bid rules allow it. A late answer in an addendum still helps, and a late question is better than a silent guess.

Can I just note the conflict in my proposal and price the cheaper version?

That is risky. On work where qualifications are limited, a note may not protect you, and after award the complementary documents rule can be read to require the greater scope anyway. If you price the lesser scope, know that it is a business risk, not a document reading.

Who should answer a roof plan and detail conflict?

The design team of record, through the channel the bid documents name, usually the architect or the general contractor's preconstruction contact for a subcontractor bid. Get the answer in writing, by RFI response, meeting minutes, or addendum, and keep it with the bid file.