How to Compare Extension Quotes Like for Like in Edinburgh

You have three quotes for your extension. One is noticeably cheaper than the other two. One is two pages long; another is twenty. One includes the kitchen; another says the kitchen is by the client. How do you make sense of it?

The number at the bottom is the least useful part of a quote until you understand what is behind it. Here is how to compare quotes properly, so you are choosing between builders and not between guesses.

Step 1: Make sure everyone priced the same thing

The single best way to get comparable quotes is to give every builder the same information:

The same drawings, with the same revision numbers.
The same specification, or schedule of works.
The structural engineer's details.
A clear list of what is in and what is out.

If one builder priced from an old drawing and another from the warrant set, you are comparing different jobs.

If you do not have a specification, ask each builder to list what they have assumed. Then compare the assumptions.

Step 2: Line up the scope

Make a simple table with a row for each part of the job and a column for each builder. Common rows:

Site set-up, welfare, skips and scaffolding.
Demolition and strip-out.
Foundations and drainage.
Structure: walls, steels and roof.
Windows, doors and rooflights.
Insulation and plastering.
Electrics.
Plumbing and heating.
Kitchen, whether supply, fit, or both.
Flooring.
Decoration.
External works: patio, paths and making good the garden.
Professional fees: engineer, warrant and completion certificate.

Tick what is included, cross what is not, and mark anything unclear. The gaps become obvious.

Step 3: Look for provisional sums and allowances

A provisional sum is an allowance for something not yet defined, like an allowance for the kitchen or for unknown ground conditions. They are normal, but they can make a quote look cheaper than it really is.

Check:

Which items are provisional.
How big each allowance is.
Whether the allowance is realistic for what you want.

A low allowance today becomes an extra cost later.

Step 4: Read the exclusions

Exclusions are often where the real differences are hiding. Common ones:

Building warrant and engineer's fees.
Asbestos.
Rock or poor ground.
Moving drainage.
Upgrades to the electrical supply.
Party walls, boundary or neighbour issues.
Making good inside the existing house.
Decoration.
Skip permits and parking suspensions.

An exclusion is not wrong. It just has to be priced by someone.

Step 5: Compare the programme

How long does each builder think the job will take? When can they start? A much shorter programme is not automatically better; ask how they will achieve it. A start date six months away might be the price of a builder in demand.

Step 6: Compare payment terms

Is there a deposit?
Are payments based on valuations of work done, or fixed stages?
How often?
Is retention allowed?

Payment terms that are reasonable and linked to progress are a good sign.

Step 7: Check the paperwork behind the price

Ask each builder:

Will you work on a written contract?
What insurance do you hold?
Who will manage the job day to day?
Who are the main subcontractors, and are they your regular team?
Can I speak to previous clients or see similar projects?

Step 8: Understand why the cheapest is cheapest

Sometimes the cheapest quote is genuinely competitive. Sometimes it is missing scope, has low allowances, or assumes things will go perfectly. Ask the builder directly what they have assumed that the others might not have. A good builder will answer honestly.

Step 9: Talk to them

A quote cannot tell you how a builder communicates. Meet them. Ask how they handle changes, delays and disagreements. You will be dealing with this person for months.

Red flags

No written quote, or a single line with a number.
Large cash deposits, or pressure to pay before work starts.
Reluctance to sign a written contract.
Vague answers on insurance.
No clear exclusions.
A start date that seems too good to be true.

How we quote

We price from the drawings and specification, list what is included and what is excluded, and identify provisional sums clearly so you can see where the risk sits. If something is not defined yet, we will tell you, and explain how it will be priced once it is.

If the quotes in front of you are for a house extension, compare them on the same drawings and request an estimate for that scope.

FAQ

How many extension quotes should I get? Three is common. More than that can be hard to manage and compare properly.

Why do extension quotes vary so much? Differences in scope, assumptions, allowances, exclusions and how busy each builder is all affect the price.

Should I always choose the cheapest quote? Not automatically. Make sure it covers the same scope as the others and that the allowances are realistic before deciding.

What is a provisional sum? An allowance in the quote for something not yet fully defined. It will be adjusted to the actual cost once known.

Can I ask builders to re-quote on the same basis? Yes. If quotes are based on different assumptions, sharing a common scope and asking each builder to confirm or revise is reasonable.