550 x 550 is a working aperture rather than an inspection hole. It is what gets specified when somebody has to get an arm and a set of tools inside and do something: a motorised valve set in a riser cupboard, a pump or strainer above a suspended ceiling, metering and control gear in a service zone, engineering services that will be maintained through the panel year after year.
It is also the largest of the square sizes that stops short of 600 x 600, which is worth noticing when the opening lands in a busy piece of lining. Every millimetre of a large hole is board you have to cut, support and make good, and where the panel falls close to a stud, a joist or a board joint, the slightly smaller square is often the one that goes in cleanly.
The trade runs the other way too. A panel this size is awkward to hold flat overhead on your own, and its frame perimeter is long enough that an untidy cut shows. If the service behind it only needs a look and a turn of a valve, the smallest stock size, 150 x 150 access panels, will do that with a fraction of the disturbance.
Fifteen products are listed at this size, the widest choice of any size category on the site. The breadth comes from two axes crossing. On one there is the door material, painted metal or plasterboard faced. On the other there is the frame, a picture frame sitting on the wall surface or a beaded frame set into the board and plastered in.
Metal doors run the full ladder, from the budget line through the standard panel to the FlipFix clamp fitting system, and each of those appears in both frames. Plasterboard doors are a beaded proposition at 550 x 550, in a standard and a FlipFix version, because the entire point of a board faced door is that it takes the same skim as the surface around it.
Fire rated lines sit across both materials. Read the notes below as a shortlist, then use the product list on this page to narrow down to the specification in front of you.
Two rungs of the same idea, a painted steel door on a hinge in a fixed frame. The budget line suits price led work where the panel is functional and out of the way. The standard line is the everyday specification. Both are listed in the picture frame and in the beaded frame at this size.
The clamp fitting version of the metal door, again in both frames. Its argument is speed of installation, and that argument is worth more on a 550 square frame than on a small one, simply because there is more frame to line up and hold true. Browse the wider FlipFix access panels range for the same system in other sizes.
Standard and FlipFix versions, both beaded. The door face is board, so it is taped, skimmed and decorated along with the wall, and the panel reads as part of the surface instead of as a fitting on it. This is the choice for circulation areas and occupied rooms, and it commits you to a plasterer. The wider family is at beaded access panels.
The 1hr rating is well covered at this size: metal doors in both frames, with and without the FlipFix system, plus two plasterboard beaded lines. The 120 minute panel is a single product, a metal door in a beaded frame with FlipFix fitting. Confirm the evidence behind the exact line against what the specification asks for, and see fire rated access panels for the rated range as a whole.
Most buyers arrive here having already typed a number, so the useful question is whether the number is the right one.
Against 600 x 600, the larger panel gives more clear opening and more room to work, and it is the one to take when a component has to come out through the hole rather than merely be reached. What it costs you is lining. A 600 square opening is a bigger hole to cut, support and make good, and in a stud wall it is likelier to run into framing. Where 600 has been chosen because it sounds like a round number, 550 will usually serve just as well.
Against 450 x 450, the smaller panel is easier to handle, easier to finish and less visible, and it is ample for a valve, a junction box or a meter that only needs to be seen and reached. It starts to fight you as soon as the work behind it wants two hands, a tool at an angle, or a part lifted clear. If you are unsure about reach, the extra 100mm each way at 550 is cheap insurance.
The full ladder is at access panels by size. An opening that matches none of the stock sizes is a made to measure access panel.
Set the opening out before you cut anything. At 550 square you are working within the spacing of ordinary stud and joist centres, so the position of the panel is often decided by the framing rather than by the service behind it. Moving the mark at setting out costs nothing. Discovering the problem with a saw already in your hand costs a sheet of board. On a ceiling, check what runs above the lining across the whole footprint of the opening rather than at the centre point alone.
Handling comes next. Plan for a second pair of hands or a prop at ceiling level, and support the cut edges of the board properly, because a long unsupported edge around a large aperture is what makes a fitted panel look wavy.
Then the finish. A beaded frame at this size has a perimeter of over two metres to scrim, tape and plaster, which is real jointing work rather than a quick patch, and the drying time belongs in the programme. A picture frame skips all of it and hands you a clean visible border instead. Neither is the better answer in general, only in a particular room.
