The interior design guide
Open Rayon

The interior design guide. A definitive knowledge base for interior designers.

From first principles to the finishing touches: shell, surfaces, space planning, furniture, electrics, plumbing and joinery, in the order a project runs.

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The Lexicon.

Every term, in plain words.

From hue and light reflectance to bonding and kick space, every term the guide uses has a short definition, what to know in practice and the pages that use it.

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The interior design guide.

A definitive knowledge base for interior designers.

Eleven chapters take a home from first principles to the moment you show it to the client. Start with Foundations and read in order, or search for a topic, a term or a rule of thumb.

Chapters.

Eleven steps, from principles to presentation.

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Where to go next.

Sections.

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Surface layout and transitions,

how materials meet, repeat and turn corners.

A material’s effect depends as much on its layout as on its look. Boards change a room when they change direction; a tiled wall looks balanced or awkward depending on where the cuts fall; a poor junction between two fine materials can dominate a room. Plan direction, module, alignment, edges and thickness together.

Orientation and direction.

Which way it runs.

Timber boards, rectangular tiles, veined stone and wall panels all have a direction, and their repetition sets the eye moving. Boards often follow a room’s main axis, or continue between connected rooms, but there is no universal rule: proportions, sightlines, the product and the substrate decide. Keeping one direction across a threshold joins two spaces; turning it separates them.

The same room, boards along it, across it and on the diagonal, and how each reads from the door.

Patterns and modules.

The piece plus its joint.

Most tiled and panelled surfaces repeat a module: the size of one piece plus its joint. Planning from the module avoids awkward cuts and lines the finish up with the architecture. Some tiles limit the offsets they can take, because of dimensional variation or warpage: follow the manufacturer, rather than assume every pattern suits every tile.

Six patterns in identical pieces, so only the geometry changes.
PatternCharacteristicsTypical use
Straight layRegular aligned gridStone, ceramic and porcelain tile
Running bondOffset parallel coursesBrick, wall tile, flooring
HerringboneRepeating zigzag of rectangular piecesTimber, parquet, rectangular tile
ChevronAngled pieces meeting along a straight axisParquet, decorative floors
BasketweaveInterlocking groups of rectangular piecesParquet and decorative tile
Modular patternA combination of element sizesStone and ceramic flooring
Try a pattern in a material, and turn it.

Setting out a tiled surface.

Where the first tile goes.

A setting-out drawing fixes where the first tiles start and how the pattern meets the room’s edges. The aim is not just fewer cuts, but cuts placed on purpose, important features aligned, and no narrow slivers where they show. Set a reference axis, work out the module, and test the edge pieces.

Take a wall 2,450 mm across, with 300 mm tiles and 3 mm joints: the module is 303 mm. Eight whole tiles and seven joints take 2,421 mm, leaving 29 mm; centred, that becomes two slivers about 12 mm wide. Seven whole tiles centred on the wall leave balanced cuts of about 163 mm at each end, a far better result.

The arithmetic uses nominal sizes and leaves out installation tolerances. On site, use measured tile sizes, the movement allowances needed and the joint specified.

Started at one corner: a 26 mm strip at the far end.
A tile centred on the wall: 163 mm cuts at both ends.

Change the wall, the tile, the joint and the start, and watch the cuts.

Aligning surfaces with architecture.

Joints that mean something.

Patterns convince when they relate to the room. Tile joints can line up with window reveals, the centre of a vanity or the edge of built-in furniture; panelling can be organised around door openings; a floor pattern can reinforce a route through the room. Not every joint must align: too many constraints add cuts and complexity, so favour the most visible axes. Large-format tiles need particular care with substrate flatness: larger pieces do not mean fewer problems.

Floor transitions and thresholds.

Where two floors meet.

A transition must resolve three things: the difference in material thickness, the change in performance, and the visible joint.

Four ways two floors meet, in section. The finished floor level, FFL, is dashed.

Flush transitions

A flush transition keeps both finished floors at one level, often best for circulation and accessibility. It means planning the whole floor build-up, not only the visible finish: tile on adhesive and timber on underlay differ in total thickness, so the layers beneath may need adjusting.

Transition profiles

Metal, timber, stone and polymer profiles protect exposed edges, absorb a change of material and can hide a small difference in height. Any raised profile on an accessible route must meet the applicable accessibility and safety requirements.

Movement joints

Materials expand, contract and respond to temperature and humidity. Floors may need movement joints at perimeters, structural joints, large areas and changes of assembly. A rigid grout or hard filler cannot take movement; position, width and treatment depend on the product, substrate and relevant standards.

Wall-to-floor and wall-to-ceiling junctions.

Where construction shows.

At the floor, skirtings hide perimeter gaps and protect walls from cleaning and knocks; wet areas may need coved or sealed junctions, depending on the waterproofing. At the ceiling, a plain painted corner is restrained; cornices, shadow gaps and recesses mark the change, or separate ceiling from wall. A shadow gap is not an omitted strip: it needs a support system, a formed edge, and thought for movement, fire and acoustics.

Six junctions, drawn at one scale.

Surface continuity and visual hierarchy.

Not every surface should compete.

A continuous floor can join several spaces, while a change of wall material can mark an activity or an architectural feature. Choose which transitions to emphasise and which to quieten: a strong change can make a threshold or a zone, a discreet joint keeps continuity. Resolve the hierarchy together with the technical needs: sometimes a joint is required where an unbroken surface would look better.

Checklist.

Before the layout is fixed.

Check each surface’s layout and every place it meets another. Your ticks are kept in this browser.

Layout and transitions

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Where to go next.

Previous

Surface types and properties

Next

Surface documentation

Units