Alcoves are the most useful awkward space in a British home. Either side of a chimney breast, tucked beside a bay window, or squeezed in next to a doorway, they are usually the right size for books and the wrong size for almost anything you can buy. Two options come up again and again: floating shelves, or built-in shelving that fills the gap properly. They ask different things of your budget, your toolbox and your landlord, and they suit different rooms. Here is how to work out what your alcove is actually asking for.

What each option really involves

Both look simple in photographs. Both have a fiddly bit that decides whether the result looks deliberate or homemade in the wrong sense.

Floating shelves

A floating shelf is a board with no visible support. Behind it sits either a steel rod bracket that slots into holes drilled into the back of the timber, or a timber frame fixed to the two side walls and the back wall, with the shelf built as a hollow box that slides over it. Either way it relies on solid fixings at each end, plus one or two along the back.

Built-in shelving

Built-ins are a frame first, shelves second. Two vertical panels down the sides, a top and bottom, then either fixed shelf positions or drilled holes for adjustable pins. Add edge banding or a face frame at the front, scribe the sides to the wall, then fill, prime and paint. Done well, it reads as part of the house rather than furniture that happens to be standing there.

Cost: where the money actually goes

Two or three floating shelves are usually the cheaper project. The timber is modest, and you can often get away with one trip to a timber merchant. The cost climbs when you buy the hidden bracket systems, which are not cheap, and climb again when you buy a cheaper one and watch it sag under the weight of hardbacks after a year.

Built-ins use more material. A full-height alcove run typically swallows several sheets of sheet material, plus pins, screws, edge banding and paint. The bigger difference is time: cutting, scribing, assembling, filling and painting a built-in can take a weekend or several. The consolation is that it uses the whole alcove, including the dead space above head height and the full depth at the bottom.

Material choice matters for both. MDF paints beautifully and machines easily, but it sags over a long span unless the shelf is thick or supported. Plywood is stiffer for the same thickness. Solid timber looks lovely and moves with the seasons, which is fine on a shelf and annoying on a long span in a centrally heated room.

Tools and skill level

Neither job needs a workshop, but they need different skills. Floating shelves are less about woodworking and more about fixing and level. Built-ins are about squareness, scribing and a tidy finish at the edges.

For either project, you will want:

• A long spirit level, ideally around 1200mm, not a stubby one
• A tape measure and a combination square
• A drill, plus an SDS drill and masonry bits if you are going into brick
• A pipe and cable detector, because alcoves hide central heating pipes and sockets
• A circular saw or a fine-tooth hand saw, plus a straight edge
• A countersink bit, wood screws and a driver
• Filler, decorator's caulk, primer and paint

Floating shelves punish sloppy measuring. If the fixing points at each end are out of level, the board will not sit flat, and there is no trim to hide it. Built-ins punish sloppy scribing. Old houses rarely have square corners or plumb walls, so the side panels usually need cutting to follow the wall rather than expecting the wall to meet the panel.

Rentals: what you can take with you

If you rent, read your tenancy agreement before you buy timber. Many agreements require permission for wall fixings, and some ask for the wall to be made good at the end of the tenancy. Both options leave holes; the question is how many.

Floating shelves generally leave fewer. A few well-placed fixings per shelf, filled and touched up, is a small repair. A built-in run may need battens or uprights fixed along the full height of the alcove, which means more holes and possibly a length of new skirting where you had to cut around it.

There is a third route worth considering: a free-standing alcove unit sized to the gap, held with a single anti-tip strap. It keeps the fixings to a minimum, moves house with you, and can be sold on later.

Storage and how the room feels

Floating shelves suit lighter loads and a calmer look. They keep the floor visible, which makes small rooms feel bigger, but they offer less usable volume because there is no structure around the contents. Things can fall off the ends, and heights are fixed once you drill.

Built-ins hold more and hold it more tidily. You can run shelves to the ceiling for rarely used items, work in a cupboard at the base for the ugly stuff, and drill adjustable pin holes so the shelf heights can change as your needs do. The trade-off is visual weight. A deep alcove filled floor to ceiling will make a narrow room feel narrower.

A quick decision guide

• Choose floating shelves if you want a lighter look, you are renting or planning to move, your budget is tight, and you mainly store books, plants and a few boxes.
• Choose built-ins if the alcove is a permanent feature of your home, you need serious storage, you want adjustable shelf heights, and you are happy to spend a weekend or more on finishing.
• Mix the two if you want storage without the bulk: a low built-in cupboard at the base with floating shelves above it is a common and practical compromise.

Before you commit, do three things

First, measure the alcove at three heights and three depths. The width at the top is often different from the width at the skirting, and a shelf cut to the narrowest point will leave gaps at the widest.

Second, tape the proposed shelf positions onto the wall with masking tape and live with them for a few days. It is surprising how often a shelf that looked right on paper sits exactly where a lamp, a radiator pipe or a light switch needs to be.

Third, decide what will actually go on the shelves before you choose the thickness and span. Heavy art books and a record collection demand a stiffer shelf and closer supports than a row of paperbacks. If you are unsure about fixings into an older wall, or you are drilling near pipes or wiring, bring in a qualified tradesperson rather than guessing.

Photo: Vilkasss / Pixabay