The second rooflight shown on the plan but missing from the price

The project

A homeowner appoints a builder for a single-storey rear extension.

The planning drawing shows two rooflights. The builder's quotation says:

Supply and install one rooflight, allowance £1,450.

The quotation also says:

Works to architect's drawings.

Nobody lists the drawings or resolves the inconsistency.

What happens

After the contract is accepted, the architect issues a building-regulations drawing. It still shows two rooflights. The builder orders one.

When the roof is framed, the customer asks where the second opening is. The builder says a second rooflight is extra. The customer says two have always been on the approved plans.

Adding it now affects the trimmers, membrane, internal finish, product order and programme.

Customer perspective

The customer gave the builder the plans and accepted a price for the extension. “Works to architect's drawings” appeared to confirm that the design was included.

They noticed the one-rooflight line but read it as an allowance or product reference, not an exclusion of the second opening. They did not know they were expected to reconcile the quotation against every symbol on the plans.

Trade perspective

The builder listed one rooflight and priced one. They believed the specific quotation item took priority over the general drawing reference.

The building-regulations drawing arrived after pricing. They did not regard its issue as an instruction to add unpriced work.

Designer perspective

The architect intended two rooflights throughout. They believed the revised drawing coordinated technical information, not that it changed the accepted design. They were not administering the price and did not see the final quotation.

Nobody needed to be dishonest

Each participant used a different source as the project truth:

• customer: the approved planning drawing;
• builder: the priced quotation item;
• architect: the current design drawing.

The project had information but no controlled information relationship.

The better pre-contract record

The quote review should have flagged:

Drawing A101 P2 shows two rooflights. Quotation item R14 prices one rooflight. Confirm the required quantity and update the scope, allowance and document set before acceptance.

The parties could then choose one of three clear outcomes:

1. 1two rooflights are included and the quote is revised;
2. 2one rooflight is included and the drawing is corrected, subject to planning and design review;
3. 3the second rooflight remains an option with a stated price and decision date.

If the conflict is found after acceptance

The project should:

1. 1identify the accepted quotation and drawing revisions;
2. 2record the discrepancy without assigning fault prematurely;
3. 3ask the responsible designer whether one or two is technically and regulatorily acceptable;
4. 4identify the work already carried out and any avoidable rework;
5. 5set out the price and programme positions separately;
6. 6record the agreed resolution and revised document;
7. 7preserve every earlier version.

The existence of a drawing does not decide legal liability or payment entitlement. It provides part of the evidence needed to understand what each party reasonably thought had been agreed.

Shared lesson

A drawing conflict should become a question before it becomes work, cost and blame.