Garage gym: keep the door, replace it or brick it up?

Why the door matters

The garage door is the largest single opening in the room and usually the weakest point. A typical metal up-and-over door is uninsulated, rattles in the wind and leaks air around every edge. Whatever we do to the walls and ceiling, the room will not stay warm and dry unless we deal with the door too.

There are three ways to do that. Each has real advantages and real trade-offs, and the right answer depends on your house, your budget and how you plan to use the room. Here is how they compare.

Option 1: keep the door and insulate behind it

We build an insulated stud wall just inside the existing door, boarded and plastered on the gym side. From the street, nothing changes: the house still has a garage door. Inside, the door disappears behind a finished wall.

This is the cheapest option and the one we include in our starting specification. It rarely needs planning permission, because the outside of the building stays the same, and it keeps things simple if the house has a condition protecting the garage for parking. The wall can be removed in future if a buyer wants the garage back.

The trade-off is that you lose the door as a way in and out and as a source of fresh air. The room relies on its other door and on ventilation, so we always fit an extract fan and background ventilation. You also lose a little length from the room.

Option 2: replace it with an insulated door

We remove the old door and fit an insulated sectional or roller door. These are made from insulated panels with proper seals around the edges, so they perform far better than a metal up-and-over door. From the street, it still looks like a garage, often a smarter one.

The big advantage is flexibility. You can open the door on a warm day and train with fresh air, move large kit in and out easily and, if you ever want to, put a car back in. A roller or sectional door also frees the ceiling space taken by an up-and-over track, which matters in a low garage.

It costs more than an internal wall, and even a good insulated door does not perform as well as a solid insulated wall. Replacing a door like for like does not usually need planning permission, though we check for conservation areas and conditions.

Option 3: brick up the opening

We infill the opening with a new wall on proper foundations, usually with a window, a door or both, insulated and finished to match the rest of the room. This gives the warmest, most solid room and lets daylight in, which makes a real difference to how the space feels.

It is the most involved option. The new wall needs foundations, a damp-proof course tied into the existing one and building regulations approval. Because it changes how the house looks, it can need planning permission in conservation areas or where permitted development rights have been removed. It takes longer and costs the most. Matching the existing brick also matters, because a poor match is obvious from the street.

Side-by-side comparison

Here is how the three options compare on the points that matter most.

• Cost: keeping the door is cheapest, replacing it sits in the middle and bricking up costs most.
• Thermal performance: a bricked-up wall performs best, an insulated wall behind the door comes close and an insulated door is good but not as good as a solid wall.
• Light: bricking up with a window adds daylight; the other two rely on existing windows and artificial light.
• Planning and building regs: keeping the door rarely affects planning; replacing it usually does not; bricking up needs building regs and can need planning.
• From the street: keeping or replacing the door keeps the garage look; bricking up changes the front of the house.
• Resale: keeping or replacing the door means a buyer can easily return the space to a garage; bricking up gives a finished room but removes the garage.

Parking conditions on new estates

On many newer estates, the planning approval for the house includes a condition that the garage stays available for parking. Bricking up the door, and in some cases converting the garage at all, can breach that condition. Keeping or replacing the door makes it easier to show the space could still be used as a garage. We check the planning history for your address before we quote. Our planning permission guide covers this in more detail.

Which option we recommend first

For most garages, we recommend keeping the door and insulating behind it first. It is the lowest-cost route to a warm, finished gym, it avoids planning questions and it keeps the outside of the house unchanged.

An insulated replacement door suits people who want to open the room up in summer, or who may want the garage back later. Bricking up suits people who want daylight from a new window and a room that feels part of the house, and who have no parking condition to worry about. We price the options at the survey so you can decide with real figures in front of you. Our insulation guide explains how each option affects warmth.