Access Panel Sizes: UK Size Chart and How to Choose
Ordering the wrong size is the most common mistake with access panels. The figure on the box is the panel size, not the hole you cut and not the space you get to reach through. This guide explains the three measurements that matter, gives a full UK size chart for the FlipFix panels we stock, and walks through how to pick the right one for a stopcock, a valve cluster, a fan or a ceiling void.
The three measurements: panel size, structural opening and clear opening
- Panel size is the nominal size you order, for example 450 x 450mm.
- Structural opening is the hole you cut in the plasterboard. FlipFix's fitting instructions say to cut it 5mm larger than the panel size each way, so a 450 x 450mm panel goes into a 455 x 455mm hole.
- Clear opening is the usable gap with the door open at 90°. Because the frame and door take up room, it is smaller than the panel. FlipFix gives it as panel size less 50mm each way on metal faced panels, and less 50mm by 75mm on plasterboard faced panels.
The clear opening is the number to design around. A 150 x 150mm metal faced panel only gives you about 100 x 100mm to reach through, which is fine for a single isolating valve but not for getting a hand and a spanner round a manifold.
Access panel size chart (FlipFix)
All sizes are in millimetres. Prices are ex VAT at the time of writing; "PB" means plasterboard faced, beaded frame; "Metal" means metal faced, picture frame.
| Panel size | Hole to cut | Clear opening (metal) | Clear opening (PB) | Metal, non fire rated | Metal, 1 hour | Metal, 2 hour | PB, non fire rated | PB, 1 hour |
|---|---|---|---|---|---|---|---|---|
| 150 x 150 | 155 x 155 | 100 x 100 | 100 x 75 | £14.15 | £19.82 | £20.62 | £28.02 | £45.84 |
| 200 x 200 | 205 x 205 | 150 x 150 | 150 x 125 | £17.02 | £20.43 | £21.15 | £29.48 | £45.84 |
| 300 x 300 | 305 x 305 | 250 x 250 | 250 x 225 | £23.38 | £27.82 | £30.03 | £34.94 | £54.35 |
| 350 x 350 | 355 x 355 | 300 x 300 | 300 x 275 | £29.15 | £32.28 | £41.95 | £40.44 | £60.50 |
| 400 x 400 | 405 x 405 | 350 x 350 | 350 x 325 | £31.23 | £38.69 | £43.42 | £41.58 | £64.99 |
| 450 x 450 | 455 x 455 | 400 x 400 | 400 x 375 | £36.40 | £44.05 | £46.37 | £44.82 | £69.32 |
| 500 x 500 | 505 x 505 | 450 x 450 | 450 x 425 | £39.38 | £47.67 | £50.25 | £49.78 | £71.78 |
| 550 x 550 | 555 x 555 | 500 x 500 | 500 x 475 | £42.49 | £50.80 | £53.84 | £48.48 | £72.34 |
| 600 x 300 | 605 x 305 | 550 x 250 | 550 x 225 | £36.40 | £43.99 | £48.88 | £44.17 | £67.43 |
| 600 x 600 | 605 x 605 | 550 x 550 | 550 x 525 | £42.92 | £53.49 | £62.37 | £50.84 | £85.00 |
| 900 x 600 | 905 x 605 | 850 x 550 | – | £92.48 | £116.74 | – | – | – |
| 1200 x 600 | 1205 x 605 | 1150 x 550 | – | £102.17 | £134.14 | – | – | – |
Clear openings are worked out from FlipFix's published formula, so treat them as a guide and check the datasheet for the exact panel you order. Bespoke sizes are made to order: call 03330 908479 for a price.
How to choose the right size, step by step
- Decide what has to come through. A hand to turn a valve? Two hands and a tool? A head and shoulders to look along a ceiling void? A fan unit or pump that may need replacing? Write down the clear opening you need, not the panel size.
- Add the frame. For metal faced panels add 50mm to each clear dimension; for plasterboard faced panels add 50mm to one and 75mm to the other. Round up to the next stock size.
- Check the framing. The hole is panel size + 5mm. Make sure it fits between studs, joists or ceiling channels without cutting them. On a 600mm stud or joist spacing, a 550 x 550mm panel (555mm hole) can be awkward once you allow for the thickness of the studs themselves, so measure the actual gap.
- Check the depth. The frame sits behind the board: FlipFix gives a frame depth of 50mm for the metal faced panels and around 56–60mm for the plasterboard faced panels. Make sure no pipe, cable or noggin sits in that zone.
- Check the board thickness. The FlipFix clamps grip boards from 8mm to 32mm on metal faced panels and 12.5mm to 32mm on plasterboard faced panels, which covers single and double layers of standard 12.5mm and 15mm board.
- Check fire rating limits. If the wall or ceiling is fire-resisting, choose a fire rated panel and stay within the tested size range (see below).
Typical sizes for common jobs
- Single stopcock or isolating valve: 200 x 200mm or 300 x 300mm.
- Bath or shower trap, boxed-in valves: 300 x 300mm to 400 x 400mm.
- Manifolds, meters, junction boxes and extractor fans: 400 x 400mm to 500 x 500mm.
- Ceiling voids you need to look along or work in: 600 x 600mm, or 900 x 600mm / 1200 x 600mm metal faced panels for plant and duct access.
- Narrow riser or between-stud access: 600 x 300mm, fitted portrait in a wall.
The commonest mistake is going too small. Many installers default to 450 x 450mm or 500 x 500mm because the price difference over a 300 x 300mm panel is small compared with the cost of opening up a wall later.
Fire rated sizes
FlipFix fire rated panels are tested at 600 x 600mm, and that is the assessed maximum on the standard datasheets with no increase permitted. In our range, the 1 hour and 2 hour metal faced panels and the 1 hour plasterboard faced panel all come in sizes up to 600 x 600mm. The 1 hour metal faced panel is also listed at 900 x 600mm and 1200 x 600mm, and FlipFix publishes a separate specification sheet for those sizes, so check it against your project before specifying them for fire rated use. Our fire-resistant drylining guide covers the wall and ceiling side of the build.
Frequently asked questions
Is an access panel size the hole size?
No. The size is the nominal panel size. For FlipFix panels you cut the hole 5mm larger each way, and the usable opening is smaller again.
What is the most popular access panel size?
For general plumbing access in houses, 300 x 300mm to 450 x 450mm are the usual choices. 600 x 600mm is common in ceilings.
Can I fit a large panel in an existing hole?
Measure the hole at both ends and both sides, take the smallest figures, subtract 5mm, and choose the stock size at or below that. If the hole is too big for one size and too small for the next, patch the board and re-cut.
Do you make non-standard sizes?
Bespoke sizes, locks and colours are made to order by FlipFix. Call 03330 908479 for a price.
Order access panels
Browse all our access panels or the full FlipFix range. Every panel can be ordered singly, prices are shown ex VAT at trade prices, and you can order online or call us on 03330 908479 for bespoke sizes or project quantities. Popular picks: the metal faced non fire rated panel from £14.15 and the metal faced 1 hour fire rated panel from £19.82.
Delivery: access panels are £15 + VAT per order under £300 ex VAT and free from £300 ex VAT. Most orders over £400 + VAT are delivered free across England, with delivery to mainland Wales and Scotland too. Mainland Wales and mainland Scotland: Celotex insulation and Knauf loft roll have £40 ex VAT delivery on every order; ceilings have a £400 ex VAT minimum plus £40 ex VAT delivery; British Gypsum plaster and plasterboard have a £400 ex VAT minimum plus £40 ex VAT delivery. We do not deliver to Northern Ireland or the Scottish islands.
Sources: FlipFix datasheets and fitting instructions for FF/000/MD/PF/FL, FF/060/MD/PF/FL, FF/120/MD/PF/FL, FF/000/PD/BF/BL and FF/060/PD/BF/BL (FlipFix downloads); HM Government Approved Documents (gov.uk). Prices ex VAT and correct at the time of writing.