The 300 x 300mm panel is the classic small inspection hatch, sized for stopcocks, isolator switches and boiler flue access points. It is available in budget plastic, steel and fire rated versions, and it is the size most often bought in multipacks for recurring snagging and maintenance work. Choose your door type below.
Three hundred millimetres square is the small hatch that most domestic and light commercial work is built around. It is sized for reaching one fitting rather than working on an assembly: a hand and a wrist go through comfortably, a forearm at a push. That is what the majority of concealed services actually need, and keeping the aperture small means less disruption to a finished surface, less making good afterwards, and a panel that reads as a neat detail instead of a hole in the room.
You will find this size in bathrooms, airing cupboards, kitchen bulkheads, boxed in pipe runs and hallway ceilings, wherever the thing behind the finish is a single valve, switch or joint that somebody needs to reach once or twice a year. If you are specifying these for the first time, what is an access panel covers the basics of how a frame and door assembly works before you commit to a size.
Three jobs account for most panels at this size. In each case the panel exists so a fitting can be reached without breaking into the finish, which matters more than it sounds when the alternative is cutting and reinstating a tiled wall.
Internal stopcocks, isolating valves under a bath or behind a boxed run, and the connections back to a shower valve. The opening only has to admit a hand and a spanner, so a small panel keeps the tiling or panelling around it intact.
Fan isolators, shower switch connections and junction boxes above a ceiling. These are inspected far more often than they are worked on, so sight and reach are what count, and a lockable door keeps the fitting shut away in a domestic setting.
Concealed flue runs and boiler pipework in voids and bulkheads. Where an engineer has to see a concealed flue joint, the position and the rating of the panel matter as much as the aperture, so agree both with a qualified heating engineer. Our article on why gas flues need inspection access explains the background.
Rated panels are listed at this size in both materials. The one hour versions come as a steel door or a plasterboard faced door, with either frame style, and there is also a two hour steel door in a beaded frame. Concealed flue routes and service voids in habitable rooms are the situations where a rated panel is most often called for, but the requirement comes from the construction the panel sits in, never from the size of the panel itself. Take the rating from the specification, or from the engineer or building control officer signing the work off. The wider rated selection is at fire rated access panels.
For unrated work there are three routes at 300 x 300. A standard metal door gives a hard wearing steel face that takes cleaning and frequent opening, which suits bathrooms and utility rooms. A plasterboard faced door is skimmed and decorated with the wall, so the panel all but disappears in a hallway or bedroom ceiling. A budget metal door panel, listed here with either frame type, covers cupboards, lofts and anywhere the panel is out of view. Cheaper again, in a different material, are budget plastic access panels.
Cut the aperture a fraction larger than the panel so the frame seats square, and take the structural opening dimension from the listing for whichever panel you order, rather than applying one general allowance to every job. At 300 x 300 there is very little room to correct a cut that has wandered, and on a tiled or plastered surface a square, clean hole is most of the finished result. If you are fitting an overlapping frame for the first time, how to install a metal access panel walks through the sequence in order.
Locking deserves a thought at this size, because these panels often end up in rooms that tenants, guests or the public can walk into. The options listed on the product pages start with a budget lock turned by a tee key, enough to hold the door shut and keep casual hands off the fitting, and go up from there where whatever is in the void should stay closed.
Refurbishment and maintenance work rarely needs a single panel. Where the same specification repeats across several rooms or several properties, multipack pricing is available on selected lines in discounted multipacks.
