The most common mistake people make is getting the measurements incorrect and it is the most avoidable mistake. If a roller garage door comes too wide or too narrow for the opening it can cause delays and return costs or reorder the whole garage door. Spending an extra 10 minutes measuring is time well spent.

Measuring the Opening

When measuring an opening, the most important dimensions to look at are the width and height. This refers to the opening itself, and not the overall dimensions of the garage wall or the frame; width should be measured horizontally from brick to brick, and height vertically from the floor to the bottom of the lintel.

Measure width at three locations: the top, middle, and bottom. Measurement openings can be out of square and the smallest measurement will determine the width. The same applies to height, so measure each side and use the smallest measurement.

When taking your measurements, be sure to record all three width measurements, not just the smallest. To the supplier, this will be helpful, as it can impact how the door is specified. If there is a variance of 10 mm, or more, you should note it and discuss it with the supplier before placing the order.

When it comes to measurements people overlook, headroom is another one. Roller garage doors coil upwards into a drum box that sits above the opening. That box needs somewhere to go. Most systems require 200mm to 300mm of headroom above the opening. This varies depending on the door size and manufacturer specifications, so check instead of assuming. If headroom is tight, it is not automatically a deal breaker, though it does limit the options available.

Side room is important as well. The motor housing and guides require clear space on one side, usually about 150mm to 200mm at a minimum. Garages that have pipework, fuse board, or similar obstructions close to the opening are problematic in that regard.

Face fix and reveal fix

This is a choice that will impact the overall aesthetics of the door from the exterior, as well as its position within the opening. A face fix means the guide channels will mount flush with the wall around the door opening. Reveal fix means that they sit inside the reveals. Reveal fix presents a neater overall appearance, while face fix is sometimes the only practical choice when the reveals aren’t deep or are uneven.

This is something closing to the edge. It will impact the width of the door and how the measurements will be done.

What the installer does

Let’s just say professional fitting is the right choice — especially for electric doors — the installer normally wants to do his measurements post door manufacturing. Trustworthy suppliers either send someone out or request a detailed measurement sheet with actual pictures. It isn’t a distrust of the homeowner, just how the industry deals with the costs of mistakes.

Usually on installation day, the same sequence of tasks is done. First the guides go up and are fixed to the reveals or face of the opening. The drum box and motor assembly — for electric doors — is mounted up with it. Then the door curtain is wound onto the drum and fed into the guides. The last checks are related to the travel limits, an equipped auto-stop and the manual override, which must all be accessible and functional before anyone signs off on the job.

Installation for a standard single door typically takes 2-4 hours. A double door, a more complicated install, like odd headroom or non-standard opening, may take longer.

There are a few things you should check for before the installer leaves.

One is the manual override. If the motor fails or there is a power outage, you must be able to open the door by hand. They should show you how to do this.

Another is the bottom seal, which rests along the bottom of the door and takes a lot of abuse, especially on uneven floors. Make sure it is making contact to the floor evenly.

Check the distance between the door and the drum box when the door is open. If there isn’t enough distance for the door to move without the curtain clinging to it, this is important.

Most installations happen without problems, but you should know what to check for to have a better idea of what is going on.