The Short Answer
Choose the roofer who surveys before they price, gives you one itemised written quote, can show you photographs of their own work, is a member of a trade body you can check, and does not ask for money before they have started. Then call one of their reviews.
They Go Up and Look
A price from the pavement is a guess. A proper roofer gets on the roof and into the loft, photographs what they find and goes through it with you. If someone quotes without looking, or looks only from a ladder at the front, that tells you how the work will be done.
One Written Price
Itemised, so you can see what the scaffold is, what the materials are and what the labour is. Not a figure on a text message. And it should stand: if something turns up once the roof is open you should get a photograph and a price for that before it is touched, not a bigger bill at the end.
A Trade Body You Can Check
We are members of the Confederation of Roofing Contractors, member 8125, which you can check on their website, and we are checked and monitored by Checkatrade. Membership is not a guarantee of anything by itself, but a roofer who is not a member of anything has chosen not to be answerable to anyone.
Their Own Photographs
Ask to see photographs of jobs like yours. Not stock pictures, not a brochure: their own roofs, with their own scaffold in the shot. Every photograph on this website is one of ours.
Reviews You Can Call
Google reviews are useful because the reviewer is a real account. Better still, ask for the number of a recent customer with a similar job and call them.
Warning Signs
A knock on the door saying they noticed something wrong with your roof. A price that needs deciding today. Cash only. No address. A quote for a new roof when you called about a leak. Sealant smeared over lead as a repair. Any of those and we would say thank you and close the door.
What We Would Ask
Will you survey it first? Will the quote be itemised and in writing? What happens if you find something once the roof is open? Can I see photographs of similar jobs? Which trade body are you with? Who do I call if there is a problem afterwards? A good roofer will have an answer to all six without thinking.