Garage conversion cost: what moves the price and how to compare quotes

Why a figure over the phone would only be a guess

Almost everyone asks for a price in the first conversation. It is a fair question. The trouble is that a number quoted without seeing the garage is a guess, and a budget built on a guess tends to come apart.

Picture two garages on one road. The first has a dry, flat slab and a door opening in good order. The second has a floor that falls towards the door, damp patches along the base of one wall and a boiler flue crossing the back corner. Once finished they could look identical, yet the work hidden behind the plaster is quite different.

That is why you will find no price lists on this site. We would sooner come to your home, measure up and look closely, then put a fixed price in writing that you can plan around. The visit and the quote are free.

If you want to talk it through first, you can contact us by phone or email and describe the garage. We will tell you what we need to look at on the day.

What the garage itself brings to the job

Size sets the baseline. A deeper or wider space needs more insulation, boarding, plaster, flooring and heat output, and a double garage is a bigger undertaking than a single. How you want to divide the space matters too, since an extra partition adds work even when the footprint stays the same.

Condition is next. An uneven slab has to be levelled before a floor goes down. Walls that were never meant to stay dry need treatment. A tired roof covering may need attention before you fit a ceiling beneath it. We look for all of this during the survey, so it appears as a line in your quote and does not turn up as a surprise later.

Access also counts. A wide drive and a clear route in make deliveries and waste removal simple. A garage at the end of a narrow passage means materials travel further by hand, and that takes time.

Structural alterations carry the widest swings

Taking out the garage door leaves a large gap in the front of the house. It has to be filled with a properly built wall that includes insulation and, usually, a window. Because this changes the structure, an engineer designs it before anyone picks up a trowel.

Opening the garage into the house is a bigger step. The wall between the two spaces often carries load, so a steel beam goes in to hold up what sits above, sized from the engineer's calculations. This is common when the new space is a living room, and our page on converting a garage to a living room explains why.

Below ground, the new front wall needs a base that can carry it, and the engineer judges whether the existing footings will do. Overhead, a pitched roof with trusses may offer extra headroom, but nobody alters it until the engineer has seen what the timbers support. We describe each of these steps in our process guide.

How the room you choose adds or removes work

A bedroom with an en-suite needs a waste pipe that reaches a drain, so the position of your drains can matter a great deal. A home office wants extra sockets and data cabling. A gym asks for a floor that takes weight and for decent airflow. Each use brings its own list of jobs.

Heating shows how one choice changes the work. Extending an existing radiator circuit is often the simplest route. If the boiler sits at the opposite end of the house, electric panels or underfloor heating may suit better, and we talk the options through with you.

Electrics need a check as well. A consumer unit with no spare ways has to be dealt with before new circuits go on. Windows and doors are further decisions. A bigger window lets in more daylight but costs more than a small one, and a separate entrance for an office needs its own frame, opening and lock. We show each of these as a separate line so you can see its effect.

What goes into a fixed-price itemised quote

After the survey you receive a written quote that sets the work out line by line. Structure, insulation, windows, electrics, heating, plastering and finishes each have their own entry, so nothing is lumped together.

The quote also covers the paperwork that people often forget. On our side, we send in the Building Notice or full plans, appoint the Building Control inspector and a structural engineer wherever the structure changes, liaise with both, and give you the completion certificate once the job is signed off. Our team is fully insured.

Fixed means fixed. If you ask for a change once work is under way, we explain what it involves and agree it with you in writing before we do it. Because the list is itemised, you can also adjust the scope yourself, dropping one feature or adding another, until the quote suits you.

Putting two or three quotes side by side

Collect more than one quote if you wish, then check that each covers the same ground. A low total that quietly omits the engineer, the inspector or the electrical certificate is not a fair comparison, and the missing items land on you later.

See whether the quote is itemised. One lump sum says little about what you are buying and makes any disagreement hard to settle. Find out, too, who deals with Building Control. If the answer is you, that means extra work and extra risk on your side.

It also helps to know what a competent firm checks before it quotes, which is why our planning permission and Building Regulations guide is worth reading. Last, ask what happens if the engineer's design alters the scope of the job. You want a clear answer before you sign.

A typical single garage conversion takes two to three weeks on site, and we confirm the timing when we send your quote.