How to measure an alcove for shelving

Measure the alcove’s width at the top, middle, and bottom, its depth on both sides, and its height, then mark the skirting, sockets, and anything else on the walls. Use the narrowest width, because few alcoves are square, and find out what the back wall is made of before you order.

That is the short version. The rest of this guide explains each measurement, how to turn the figures into a shelf size, and the mistakes that leave gaps, wobbles, or shelving that will not go in.

What you need

• A steel tape measure.
• A spirit level.
• Pencil and paper, or the measuring sheet in our free planning guide.
• Your phone, for photos.
• A second person, if the alcove is tall or the tape keeps bending.

Measure in millimetres. Makers work in millimetres, and it saves converting later.

How to measure an alcove, step by step

A chimney breast usually leaves an alcove on each side, and the two are rarely the same. Measure each alcove on its own, and write the figures down as you go.

1. Measure the width at three heights

Measure across the back wall, from one side wall to the other, at the top, middle, and bottom of the space the shelving will fill. Then do the same at the front, level with the face of the chimney breast. Write down all six figures.

Use the narrowest. Old walls taper, bow, and lean, so an alcove can be 10 mm narrower at the top than at the bottom, or narrower at the front than at the back. A unit sized to the widest figure will not go in.

At floor level, also measure the clear space between the skirting boards. Skirting narrows the alcove, and it matters if the shelving comes down that far.

2. Measure the depth on both sides

Measure from the back wall to the face of the chimney breast, at the left side of the alcove and at the right. Back walls are often not parallel to the chimney breast, so the two figures can differ. The smaller one is your usable depth.

Then decide whether the shelving should sit inside the alcove, line up with the chimney breast, or stand proud of it. Shelves that stand proud can catch shoulders and look heavier.

3. Measure the height

Measure from the floor to the ceiling at the left, centre, and right of the alcove, and note the height of any coving or picture rail. Then decide where the shelving should stop. Full-height shelving, a run that stops at the picture rail, and a low unit with space above all suit different rooms.

4. Check the walls for level and square

Hold a spirit level against each side wall and the back wall. If a side wall leans, the width changes with height, which you will already have seen in step 1. Measure the two diagonals of the back wall as well, corner to corner. If they differ by more than a few millimetres, the alcove is out of square.

This tells you how much gap a straight unit will leave at the sides, and whether shelves need to be scribed: cut to follow the wall’s shape.

5. Mark everything on the walls

Note every socket, switch, radiator, pipe, cable route, window, and door near the alcove. Measure each one from the floor and from the nearest side wall. Run a cable and pipe detector over the back wall before anyone drills it.

6. Find out what the back wall is made of

Knock across and up the wall. A solid, even sound usually means masonry. Mostly hollow with firmer lines suggests a stud wall. Hollow with isolated firm spots suggests plasterboard on dabs of adhesive, called dot and dab. Hollow and uneven across a bumpy surface suggests lath and plaster.

A knock test is only a first check. If you are not sure, confirm the construction before drilling. It decides which fixings to use and how much weight the shelving can carry, and there is no single weight rating that suits every wall.

7. Check the fireplace

If the chimney breast has a working fire or stove, check how far it must be from combustible materials, such as wood and plywood. Your stove’s manual or your installer can tell you. Keep the shelving outside that distance.

8. Take photos

Take one photo straight on, showing the whole alcove. Take another from the side, showing the depth and the chimney breast. Add close-ups of sockets, pipes, and anything else in the way. A maker can spot things in a photo that a list of numbers misses.

How to turn your measurements into a shelf size

How you size the shelving depends on the kind you are buying.

Scribed shelves and fitted joinery. Give the maker every figure, and do not deduct anything yourself. A joiner cuts each shelf to follow the walls, and decides the allowances.

A unit or a modular system. The unit’s overall width must be narrower than the alcove’s narrowest point, with room to fit it. With our shelving, allow 20 mm at each side. One of our 600 mm bays is 632 mm wide overall, rails included, so it needs an alcove at least 672 mm wide at its narrowest point.

You can set our bays to any width from 500 mm to 800 mm in 1 mm steps, and the configurator shows the overall width as you go. Match that, plus 40 mm, to your narrowest measurement. A wide alcove can take two bays side by side, sharing a rail. If your alcove needs a bay wider than 800 mm, or bays narrower than 500 mm, we price it by quote.

Our bays are straight and square. They are not scribed to the walls, so an alcove that tapers or bows will show small gaps at the sides. In most alcoves the gaps are small. In an alcove that is badly out of square, they will show, and scribed joinery is the better route.

Depth. Check the shelves and any cabinets against the depth you measured. Our shelves are 220 mm or 300 mm deep, and bookended shelves can also be 360 mm deep. Our cabinets are 360 mm deep and stand about 415 mm from the wall, so in a 300 mm alcove they would sit proud of the chimney breast while the shelves sit inside it.

Height. Our rails are 900 mm tall, or 1800 mm with two stacked, and we do not make anything taller. If you want shelving to the ceiling, that is a job for a joiner.

Common alcove shelving mistakes

Most problems start before anything is ordered. These are the most common.

1. Measuring the width once. One figure hides a taper. Measure at three heights, front and back, and use the narrowest.
2. Assuming the two alcoves match. They rarely do. Size each one on its own, even if the shelving should look the same on both sides.
3. Forgetting the skirting, coving, and picture rail. They narrow the space, stop a unit sitting flat, or cut across the shelves. Measure their height and how far they stand off the wall.
4. Making shelves deeper than the books. Most books fit a 220 mm shelf. Large hardbacks need about 300 mm, and 12-inch records need a 360 mm shelf. Deeper shelves waste space at the back and make the alcove feel crowded.
5. Spacing the shelves before deciding what goes on them. A hardback is up to about 234 mm tall, and a 12-inch record sleeve is 314 mm. On our shelving, most books need shelves 300 mm apart, top to top, and records need 400 mm. Measure your tallest items first.
6. Ignoring the wall. Drilling without knowing the wall type risks weak fixings, a cable, or a pipe. Our system is not suitable for lath and plaster walls, and we check your wall type with you before we send fixings to match.
7. Fixing too close to the corner. The corner of a chimney breast can crumble if you drill too near it. Keep fixings at least 80 mm from an exposed corner.
8. Long, unsupported spans. How much a shelf bends depends on its length, thickness, material, and load, and on how it is supported. Shorter spans bend less. Our standard bays are 500 mm to 800 mm wide. Books are heavy, so plan the heaviest things for the lowest shelves.
9. Forgetting the fire. Shelving too close to a stove or open fire is a fire risk. Check the distance before you design.

The best shelving options for an awkward alcove

The best option depends on what makes the alcove awkward. Start from the problem, not the product.

Some alcoves have more than one of these problems. A joiner can usually solve all of them at once, at a price you will only know after a visit. A system solves fewer of them, and you see the price before you commit.

Fitted or modular shelving for an alcove?

Choose fitted joinery if you want shelves scribed tight to the walls, cupboards built in with the skirting, or shelving to the ceiling. Choose a modular system if you want to see the price first, fit it yourself, and move or add parts later.

Our shelving is modular. Shelves and cabinets hang on steel pins at positions every 100 mm on wall rails, so you can lift one off and hook it back on higher or lower without new holes. For a longer comparison of the routes, read made-to-measure shelving vs bespoke joinery, or when a joiner is the better route.

Where to buy made-to-measure alcove shelving in the UK

There are three main routes.

• A local joiner or carpenter builds shelving and cupboards to the shape of the alcove and usually fits it. Expect a visit, drawings, and a quote before a price.
• Cut-to-size shelf makers cut shelves, often floating shelves, to your measurements. You fit them, and the result is only as good as your measuring and your fixings.
• Modular systems made to your width give you a set of parts sized to the alcove, which you can change later. Our roundup of UK made-to-measure and modular shelving compares eight brands, including us.

We make alcove shelving in 18 mm Baltic birch plywood, to any bay width from 500 mm to 800 mm, in our workshop in Norfolk. The price shows as you design, including VAT and delivery to mainland UK addresses. In October 2026, our one-bay Open shelving layout cost £828.34, and one bay with a cupboard cost £1,181.37. We make each order in 2 to 10 weeks, and you fit it with our manual and the fixings and tools in the box. You supply the drill. It comes with a ten-year warranty and a 60-day Home Trial.

Next step

Get our free planning guide for the measuring checklist, or send us your measurements and a photo through a fit review. We will suggest a layout and check the fit, free. If you already have your figures, set a bay to your alcove in the configurator and see the price.

Frequently asked questions

How much gap should I leave either side of alcove shelves?

It depends on the shelving. For our system, allow 20 mm at each side, so a 632 mm wide bay needs an alcove at least 672 mm wide. For scribed shelves, give the joiner your exact measurements and let them decide the allowance.

Do I measure an alcove with or without the skirting?

Both. Measure the width above the skirting, and the clear space between the skirting boards at floor level. Note the skirting’s height and how far it stands off the wall, and include it in your photos.

How deep should alcove shelves be?

Deep enough for what goes on them, and no deeper than the alcove if you want them inside it. Most books fit a 220 mm shelf, large hardbacks a 300 mm shelf, and records a 360 mm shelf.

What if my two alcoves are different widths?

Measure each one separately and size the shelving to each. With our system, you set each bay to its own alcove in 1 mm steps, so the two sides can match in style while differing in width.

What if my alcove walls are not straight?

Use the narrowest width. A straight unit will leave small gaps where the walls lean or bow. If you want no gaps at all, choose shelves scribed to the walls by a joiner.

Can I put shelving in the alcoves beside a working fireplace?

Yes, if it stays outside the distance your fire or stove must keep from combustible materials. Check the stove’s manual or ask your installer before you design.