For a detailed written quote, give each builder the same technical drawings, relevant structural design and a written scope of work. Planning drawings can support an early budget discussion. A builder pricing from them alone may need to make assumptions about how the work will be built and which items are included.
Assemble the Same Pack for Every Builder
- Existing and proposed plans and elevations. These identify what changes, including demolition, openings and the intended layout.
- Technical sections and construction details. These explain how elements such as the roof, floors and walls meet, and show where the extension joins the existing house.
- Structural information. Include the relevant drawings and calculations where beams, foundations or other structural work form part of the project. Note any conditions the builder needs to verify.
- A written specification and scope. List the work you want included, such as windows, drainage connections and making good. Say which items you will supply yourself and which need an allowance.
- A drawing register. Include the drawing names and revision numbers so builders know what to price. Issue any changes to all builders still quoting.
The technical information can also support the building control process. Ask your designer whether there are outstanding queries or design decisions before treating the pack as ready for a detailed quote. Share any planning decision and conditions that are relevant to the work.
Compare the Assumptions as Well as the Total
Ask each builder to put their price in writing and state what is included, what is excluded and what remains an allowance. Check how they have treated access, waste removal, VAT where applicable, temporary works and reinstatement of finishes. Make a short list of gaps and ask for clarification against the same drawings and specification. The Federation of Master Builders recommends giving builders detailed plans and comparing quotes on a common scope.
If some elements cannot be fixed at the quoting stage, ask what evidence would settle them and how a change will be agreed and priced. Keep the drawing list and written scope with the agreed quote or contract so you can refer back to what was priced.
Example: Two Prices for the Same Kitchen Extension
A homeowner receives two quotes with different totals. Both cover the same footprint, but one includes fitting the new doors and connecting drainage, while the other lists the doors as a separate allowance and assumes the existing drains are suitable. The homeowner asks both builders to price from the same door specification and describe the drainage assumption in writing. That makes it clear which parts of the gap reflect the price and which reflect different scopes.
If you have a planning set but need to get comparable build prices, ask Ashbridge to review the drawings and scope the technical package.