Galvanised steel staircases, drawn to fit the zinc bath

The short version

• Straight and turning steel stairs for outside, landings included.
• Hot-dip galvanised after all the welding is done. Leave it bare, or have it powder coated over the zinc.
• Sections bolt together on site. Nobody welds coated steel.
• We survey free, at your property, before anything is drawn.
• You get a written price after the survey, and it holds unless the drawing changes.
• We do the drawings for your Building Control application.
• We work within about forty miles of Warlingham.

Why we galvanise anything that lives outside

Paint is a skin on the steel. Galvanising bonds into the steel itself. When paint cracks at a weld, water gets in behind it and the rust creeps sideways where you can't see it. Scratch galvanising and the zinc round the scratch corrodes first, which keeps the bare steel covered.

We'd rather galvanise than paint anything that lives outside. In 32 years we've taken out a lot of tired outside stairs, and they nearly always go in the same places. The back of a stringer tight to the wall. The inside of a box section. Anywhere a brush never got to.

Designing a stair around the zinc bath

Molten zinc has to get into every hollow section and drain back out again. Seal up a 40x40 box post and the trapped air and moisture can split it open in the bath. So every tube and box gets vent and drain holes, at the corners that hang highest and lowest when it's dipped. Those little holes on a finished stair aren't a mistake.

The bath also limits how long a piece we can dip. A long flight with its landing often won't go in as one, so we decide on the drawing where it splits. Usually that's at a landing bearer, where the joint is strong and nobody looks at it.

Then there's the heat. The zinc runs at around 450°C, and thin sheet that heats unevenly can bow. We've had a 3mm kick plate come back with a ripple in it. Where flat plate is on show, we go thicker or fold a stiffening edge on it.

Bolted on site, never welded

Weld through zinc and you burn the coating off both sides of the joint. So the sections of a galvanised stair meet at flange plates and bolt up. We cut and drill those flanges at our workshop on Westerham Hill before anything goes off to the galvaniser, which leaves the fitting day mostly lifting and lining up.

Every hole drilled on site goes through the coating, wall anchors included. Each one gets a dab of cold-galvanising paint, a zinc-rich touch-up, before the fixing goes in. It does the job, but it's not as good as the dipped zinc, so we keep site drilling to the few holes the workshop can't do. A fire escape staircase goes together the same way.

Bare zinc, paint or duplex powder coat

Bare galvanising needs nothing from you. It comes back from the galvaniser bright and a bit patchy, and over the next few months it dulls down to an even matt grey. A lot of customers are happy to leave it at that.

If you want colour, we do it duplex: galvanised first, then powder coated over the zinc. A chip in the powder still has zinc under it, so rust can't creep along beneath the colour. Brushing ordinary paint straight onto new zinc is a different story, as it tends to flake off, and we'd talk you out of it.

Duplex adds another stage of work, so expect to see it as its own line on the quote.

Treads that suit a dipped stair

Open bar grating is the best match for galvanising. The zinc drains out of it cleanly in the bath, and for years afterwards the rain goes straight through it. Chequer plate works too. A wide sheet of it does hold water, though, and in a shady spot that means ice. Perforated plate sits somewhere between the two and looks tidier by a front door.

We won't use smooth flat plate for treads. Plain zinc is slippery when it's wet. For landings, bases and wall fixings, see our external staircase page.

A side-passage stair between a wall and a fence

One of the stairs in these photos goes up a paved side passage to a raised level at the back of the house. There's a stone wall on one side and a timber fence on the other. It's a plain straight flight with bar railings, left in bare galvanised.

Against the old stone the new zinc already looks fine, and it'll dull down within the year. There's more finished work on our installations page.

Building Control, upkeep and the survey

Galvanising doesn't change the rules. Approved Document K sets the rise, going, handrails and guarding for any new stair. The limits for a private house aren't the same as for a stair shared by flats or used at work. Our main steel staircases page has the detail.

Upkeep is light. New zinc that stays wet in its first months can grow a white powdery bloom called white rust. A nylon brush and a bit of air usually shift it, but never use a wire brush. Once a year, check the fixings at the foot and at the wall, and sweep the leaves off the grating.

We don't charge for the survey, and it's done by the people who'll build your stair. Afterwards you get a written price, and our quotations page explains what's in it. The easiest start is a couple of photos on WhatsApp to 07973 205888, with a tape held from the ground up to the top step or door. That number is for messages and photos only. If you'd rather talk, ring 07861 936 888, any day from 6am to 10pm.

Straight answers on galvanised steel staircases