Garage Door Infill in Liverpool

What does a garage door infill involve?

On most garage conversions across Liverpool, the garage door opening is the largest single change. The existing door, its frame and the timber or steel header are taken out. What sits above the opening, usually a lintel carrying brickwork or a beam carrying the roof edge, is checked and kept or replaced as needed. Then a new wall is built in the gap, tied into the existing walls on either side, with any window or door set in it.

It sounds simple, but the infill is where many older conversions went wrong. A thin wall built straight onto the garage slab, with no damp-proof course and no insulation, will crack, let in damp and stay cold however much heating goes in.

How is the new wall supported?

The Planning Portal notes that a new foundation may be needed for the new wall. Garage door thresholds vary: some have a footing running across the opening, some have only the floor slab with a thickened edge, and some have very little at all. LABC guidance says that where there is no foundation under the old door, the new wall can sometimes be carried on a suitable lintel or beam instead, spanning between the existing foundations, with the method agreed with building control.

We cannot tell you which applies until the threshold has been looked at, and sometimes opened up. What we can tell you is that the support will be decided with building control and shown on the drawings, not guessed. Excavating next to existing footings and fitting lintels or beams are structural tasks for experienced builders working to an agreed design.

How is the infill built?

A typical infill is built as a cavity wall: an outer leaf of facing brick to match the house, a cavity, insulation and an inner leaf of block or a framed wall, so it meets the insulation targets for a habitable room. LABC's garage conversion guidance gives a U-value of 0.18 W/m²K for external walls and 1.4 W/m²K for windows and doors, and building control confirms what applies to each job.

• Damp-proof courseA DPC in the infill at the right height, lapped with the new floor membrane, stops damp rising at the base of the wall.
• Ties into the piersThe new wall is tied into the existing brickwork on each side so the two move together and the joint does not crack.
• Cavity closers and traysAround the window, closers seal the cavity and help with insulation. Trays and weep holes above openings direct any water outward where needed.
• Window or doorSized for light, purge ventilation and, if needed, escape, with trickle vents for background ventilation.
• FinishMatched brick, render or cladding, chosen to suit the house and any planning constraints.

Window, door or escape window?

The infill is usually the main source of light and air for the new room. Building Regulations guidance for habitable rooms asks for openable windows for purge ventilation, with the opening area tied to the floor area, plus trickle vents or similar for background ventilation. If the room can only be reached through another room, LABC guidance asks for an escape window with a clear opening of at least 450 mm by 733 mm and the bottom of the opening no more than 1.1 m above the floor. Because the floor is often raised during the conversion, we set the window height from the finished floor level, not the old slab.

A door in the infill can suit a utility room or an annexe, but think about security and whether a window would give a more useful room. For a bedroom conversion, see garage to bedroom for the room-specific details.

Matching the front of the house

A good infill should look like part of the original house. That means a brick close in colour, size and texture, a matching mortar colour and joint profile, a window that lines up with others on the front, and sills and heads that suit the style of the house. On older properties, weathering makes an exact match difficult, and a well-chosen render panel or a set-back with a different finish can look better than a near-match that draws the eye.

If the house is in a conservation area, such as parts of Woolton village or Gateacre village, the council may take a closer interest in materials and window style. If the house is listed, listed building consent may be required. Always check with your own planning authority before changing the front elevation; our planning page explains how to go about it.

Wind-driven rain and exposed sites

A new infill faces the street and the weather, and a poorly built one will show it first. Houses near the coast, in places such as Crosby, Formby and West Kirby, see more wind-driven rain than sheltered inner suburbs. Good detailing matters everywhere, but on exposed fronts we pay particular attention to the cavity, the DPC and trays, how the window is sealed into the opening, and the quality of the pointing.

How the infill fits with the rest of the conversion

The infill is built at the same time as other work, not in isolation. The floor membrane has to lap with the DPC in the new wall, so the order of work matters; see floor insulation and levelling. The insulation in the infill should line up with the insulation added to the old garage walls, covered on our garage wall insulation page, so there is no cold strip at the junction where condensation can form.

1. We visit and look at the door opening, header, piers, threshold and how the front of the house is built.
2. We agree the support method, wall build-up and window or door with you, and drawings are prepared by an architect or architectural technician where needed.
3. Building control inspects at the usual stages, which can include the foundation or support before it is covered up.
4. The finished wall is part of the completion certificate for the whole conversion.

Integral, attached and detached garages

On an integral garage, the infill sits under the first floor, so what is above the opening needs checking carefully. On attached and detached garages, the opening often sits under a flat or pitched roof edge carried by the door header. Double garages may have one wide opening or two openings with a central pier, which changes how the infill is supported. We carry out garage conversion work across Merseyside on every type of garage and plan the infill around what we find.