Window Fitter Interview Questions UK: 8 Real Questions and What Interviewers Want

Before your Window Fitter interview, it helps to see the questions from the interviewer's side. We have picked eight from our set of 16 and added the reason each one gets asked.

Eight Window Fitter interview questions, and what the interviewer is thinking

1. What is FENSA, and why does it matter when you install replacement windows in England?

Why they ask: Compliance with Building Regulations is central to the role, and customers will ask about certification.

2. How do you measure for and survey a window opening, and what allowances do you make?

Why they ask: Accurate surveying prevents expensive remakes and poor fits.

3. How do you fix a PVC-U frame into an opening so that it is secure and weathertight?

Why they ask: Fitting quality directly affects security, thermal performance and leak protection.

4. What do the Building Regulations say about egress windows and escape routes?

Why they ask: Fire safety is a legal matter, and incorrect windows could trap occupants.

5. When is safety glazing required, and how do you identify it?

Why they ask: Safety glass in the wrong place is a serious injury risk and a compliance failure.

6. You remove an old window and find the brickwork and lintel above are cracked and crumbling. What do you do?

Why they ask: Tests judgement on unexpected structural issues and customer communication.

7. Tell me about a time you fitted a window in a difficult or awkward opening.

Why they ask: Shows problem-solving and craftsmanship beyond routine installs.

8. What does a typical day as a window fitter involve?

Why they ask: Checks understanding of the practical, customer-facing and compliance sides of the work.

A sample answer to question 1

What is FENSA, and why does it matter when you install replacement windows in England?

FENSA is a government-authorised Competent Person Scheme, which allows registered installers to self-certify that replacement windows and doors meet the Building Regulations in England, without notifying Building Control for each job. Others include CERTASS and Assure. Registered installers are assessed and inspected, and they must register each installation, with the customer receiving a certificate. This matters because a homeowner needs that certificate when they sell the property, as solicitors will ask for it. If an installer is not registered, the customer would need Building Control approval, which can be costly and may mean rework. The main regulations I work to are Part L for thermal performance, Part F for ventilation, Part B for escape routes, and Part K for safety glazing. I would also check the installation is carried out to BS 8213 and the manufacturer's instructions. If a company is registered, I make sure my paperwork, photographs and product details are accurate and submitted promptly.

Common mistake to avoid: Saying it is just a badge; Forgetting the certificate must be registered

Want the rest?

Full model answers, key points and common mistakes for all 16 questions are on the Window Fitter interview questions page. The first five are free, no sign-up needed.