Straight, dog-leg and multi-flight steel staircases

Straight flights, dog-legs and multi-flight stairs

A straight flight is the simplest stair and the cheapest to make: two stringers, a run of treads and a handrail. It needs a run of floor a little longer than the height it climbs: for a 2.7 metre floor to floor, three to three and a half metres plus a landing at the bottom.

When that run isn't there, the stair turns. A quarter landing turns it through 90 degrees; a half landing brings it back on itself, the dog-leg in most houses. Landings also break a long climb, and in a workplace Building Control will normally want one after 12 to 16 risers.

Multi-flight stairs stack landing on landing up a stairwell, a warehouse wall or on to a mezzanine. We draw the whole thing as one structure, so every flight lands where the floor is.

Stringers, treads and what they are made of

The stringers carry the stair. We use flat steel plate, usually 10 or 12mm thick and 250 to 300mm deep, or parallel flange channel where the span is long or the stair is open underneath.

What you walk on depends on where the stair is. Inside, on an architectural stair, folded steel pan treads take a timber, stone or glass infill and look clean. Outside the treads stay metal: open mesh grating drains and grips in frost, and chequer plate suits a workshop or a plant room. Stainless steel makes sense where the stair is on show or near the coast; mild steel, properly finished, does everything else for less.

A floating stair on a single spine, or treads cantilevered from a wall, is possible where the structure can take it. We check at the survey.

Building Regulations for a steel staircase

A new staircase falls under Approved Document K. In a house that means a rise between 150 and 220mm and a going between 220 and 320mm, the same on every step, with two metres of headroom and a handrail 900mm to one metre above the pitch line. Stairs in offices, shops and shared buildings have tighter limits on rise and going and need guarding 1,100mm high around landings.

Gaps in the balustrade must stop a 100mm sphere wherever children could use the stair. BS 6180 gives the sideways load the guarding must take, from 0.36 kN per metre in a house up to 1.5 kN or more in a shop.

If the stair is an escape route, Approved Document B comes into play too. We supply the drawings and structural calculations Building Control asks for.

Finishes: galvanised, powder coated or painted

Anything outside is hot-dip galvanised to BS EN ISO 1461. The steel goes into molten zinc after fabrication, so every weld, edge and inside face is coated, and hollow sections are vented and drained so the zinc gets through. Left as it is, it gives a dull grey finish that needs nothing doing to it for decades.

Where you want colour, we powder coat over the galvanising. The plant etches or sweep blasts the zinc so the polyester powder keys, then bakes it on. Anthracite (RAL 7016) and black (RAL 9005) are the usual choices, but any RAL colour is available.

Inside, a stair can be powder coated straight over blasted steel, or primed in the workshop and painted on site to match the joinery. Stainless steel is left brushed or polished and needs no coating.

What the site survey checks

Photos or an architect's drawing are enough for a written estimate within the working day. Before we draw anything, one of us comes out to measure, free of charge, anywhere in Kent, Surrey and South London.

Inside we take the floor to floor height at the exact spot, check the trimmer and the size of the opening, look at the joist direction and what the walls are built of, and work out how the stair comes into the house in sections. Outside we look at the ground where the base will sit, the wall we would fix to, where the water goes, and whether a lorry or a small crane can get near.

You get a drawing to approve and a fixed quotation that only changes if the design does.

What affects the price, and how long it takes

Height and width set the base cost, because they set the weight of steel. After that it is the number of landings, the tread type (grating is the cheapest outside, glass the dearest inside), the balustrade and the finish. Powder coating on top of galvanising is a second process at the plant, so it costs more and takes longer. Structural calculations, awkward access and a new concrete base each add something, and the quotation shows you what.

In round terms, a straight flight is a few weeks from the approved drawing to the fitting day: fabrication in the workshop, then about a week at the galvanisers, and another week if it is being powder coated. Multi-flight stairs with calculations take longer. Fitting a domestic stair is usually a day.

Commercial, industrial and fire escape stairs

Commercial jobs across Kent, Surrey and South London run from access to a mezzanine floor and a link between a shop and the flat above to plant room stairs, loading bay steps and fire escapes. These get heavier stringers, grating or chequer plate treads, tube handrails on both sides and guarding to 1,100mm.

For a fire escape the width, the landings and the doors on to the stair all have to satisfy Approved Document B, and the stair is galvanised so it does not need painting. An external escape stair also needs a base and wall fixings that will carry the load, which the survey checks. We work from your architect's package or draw it ourselves, and the structural calculations come with the drawing.

Straight answers on steel staircases