Let the sideboard set the boundaries

Before you think about frames, spend ten minutes looking at the space as a whole. The sideboard is not just a convenient place to lean things; it dictates the proportions of everything above it. As a rule of thumb, your gallery should span roughly two-thirds of the sideboard's width — so a 1.5-metre sideboard wants an arrangement about 90 centimetres to 1.1 metres across. Any wider and the art starts to feel unmoored from the furniture beneath it; any narrower and the pairing looks mean and tentative.

Next, set your vertical limits. Leave at least 15 centimetres of clear wall above the sideboard surface, and ideally 20 to 25, so you can still rest a lamp, a bowl or a small vase on top without crowding the lowest frame. Mark faint pencil lines for your top, bottom and side edges, then check that this box sits comfortably within the wall. If a radiator, plug socket or light switch intrudes, work around it now rather than discovering it halfway through hanging.

Plan it on paper before you touch a hammer

Every good gallery wall has been built twice: once on paper, once on the wall. Draw your wall to scale on graph paper, then cut paper templates for each frame and move them about until the composition clicks. Alternatively, trace around the frames onto lining paper or newspaper, cut the shapes out, and tape them to the wall in position. Live with the arrangement for a day or two — a slight reshuffle is far easier with paper than with plaster.

A few principles will help you get there quickly:

• Start with your anchor piece — the largest or boldest work — and place it just off-centre rather than dead centre, which gives the whole group a more natural, collected feel.
• Build outwards from that anchor, balancing weight and colour as you go, so one side does not end up visually heavier than the other.
• Keep a strong outer shape. You can be as loose as you like inside the arrangement, but a roughly rectangular or gently rounded outer edge stops the group from looking scattered.

Mix frame sizes and artwork styles

Variety is what makes a gallery wall interesting, but variety needs discipline. Aim for at least three frame sizes: one large anchor piece, two or three mediums, and a handful of smaller works to fill the gaps. Mixing a landscape, a portrait and a square or two creates rhythm and keeps the eye moving.

On style, resist buying a matching set. A plain black frame, a slim natural oak, a wide white mount and one brushed metal piece will sit together beautifully provided the artwork shares some thread — a colour, a subject, a mood. If your taste leans traditional, keep the frames darker and the mounts generous; for a lighter, more contemporary look, pale wood and white mounts work well. Whatever you choose, repeat one or two frame finishes across the wall so it still reads as one collection rather than a jumble sale.

Keep your gaps even and generous

Consistent gaps do more for a gallery wall than expensive frames ever will. As a working rule, leave 5 to 8 centimetres between neighbouring frames in a tight arrangement, or up to 10 centimetres if your pieces are large. Measure every gap rather than eyeballing it — a difference of two centimetres is surprisingly visible once the wall is finished.

When frames are different sizes, align at least one edge. Line up the tops of a row, or the centres, or the bottoms — just pick one rule and follow it. It gives the eye something to rest on and makes an informal layout feel deliberate rather than accidental.

Hang the centre at eye level

The single most common mistake is hanging art too high. The centre of your whole arrangement should sit about 145 to 150 centimetres from the floor, which is roughly eye level for an average adult and feels instantly right in most rooms. Note that this is the centre of the group, not of each individual frame — the middle of the cluster stays put even when the pieces around it are wildly different sizes.

Fix two hooks per frame for anything bigger than A4, spaced a third of the way in from each side. Two hooks keep a frame level and spread the weight. Use proper wall plugs for plasterboard and take note of the weight limits printed on your hooks. Run a spirit level across each frame once it is up, and erase your pencil marks last of all.

Finish the arrangement below

A gallery wall above a sideboard works as a single composition, so style the surface with restraint. Two or three objects is plenty: a lamp at one end for warm, low light, a small stack of books, a bowl or a single stem in a slim vase. Keep the tallest piece shorter than the lowest frame so nothing competes, and leave a little breathing space on either side. If the gallery is busy and colourful, keep the objects beneath plain; if the art is calm and monochrome, you can afford something with a bit more character. Get those proportions right and your sideboard will look as though it was always meant to be there.