Stainless Steel for Visible Architectural Metalwork

Visible stainless steel is accepted or rejected by eye, after it has been installed. What the client sees is a bright weld, a brushed grain that changes direction at a joint, or one upright post of a railing that is slightly out of line. The drawing may have been right, but the brief to the workshop was not. The architect may notice the fault at the final inspection, or the contractor may see the client stop in front of one joint and not the others. By then the pieces are already fixed to the wall, and "we can polish that later" has become a discussion on site about rework that nobody included in the price.

The products TH Steel makes for this work, from handrails and stairs to screens, panels and counters, are listed on the architecture and interior page. That page lists the processes. This article covers the brief: the decisions that stop a good drawing from turning into an uneven finish. If you have time for only one step before you enquire, send the drawing, and use this article as a list of the things the drawing does not say.

Mark the faces that will be seen

Architects, interior designers and contractors are usually trying to protect the design rather than teach a workshop how to weld. Even so, the workshop needs to know which surfaces a person will stand in front of and which joints sit at eye level. It also needs to know which faces end up against a wall or under a ceiling. Dressing a weld (grinding it and blending it into the surrounding finish) on every face takes many extra hours, while leaving a visible weld undressed gets the installation rejected. Both mistakes come from the same gap: nobody said which face mattered, so every face was finished to the same middle standard.

On the drawing, or in a note beside it, mark the faces that are seen. A highlighter and the words "this side is seen" are enough. Then say where a joint must disappear into a brushed or polished surface, and where it can stay a neat welded corner because nobody will look at it. The first instruction protects the installed appearance, and the second saves the hours that would otherwise go into dressing a face that ends up hidden.

Before you assume that weld colour can be wiped off later, read Why stainless steel rusts around welds. Heat tint is the coloured oxide that welding leaves on stainless steel. It is controlled while the joint is being made and dressed, and it is much harder to put right once the piece is on site.

Grain direction, joints and alignment

On adjoining panels, screens and handrails, the brushed lines run in one direction. That is why two panels that each have an acceptable No. 4 finish (a brushed finish with fine parallel lines) can look wrong once they hang side by side. One grain runs across and the next runs down, or one weld was blended harder, so the satin surface around it is duller than the panel next to it. None of that shows on a drawing that says "stainless, brushed" and nothing more. State the grain direction where the panels meet, and state it once for the whole run. If each piece is finished on its own, you may receive a set of acceptable panels that do not match when they are hung together as a wall.

A small sample of the brushed finish, with an arrow showing the grain, is clearer than the finish name alone. No. 4 covers a range, and that range only becomes obvious when two batches sit next to each other.

Alignment is a separate instruction, and it is easily buried in the same note as the finish. A staircase or a balustrade is judged as one line rather than as a collection of parts. So tell us which lines must look straight or evenly spaced once the piece is installed. Tell us too which fixings may absorb the difference between the drawing and the site. Slotted holes have to be decided before the steel is cut. We fabricate to the information we are given, and we do not install the work. We also cannot slot a hole that has already been drilled to a fixed size because someone hoped the opening would match the drawing.

Outdoor does not always mean marine

A sheltered lobby, a city balcony and a coastal handrail are three different environments, even when the drawings look the same. For most indoor and sheltered work, grade 304 is the usual starting point, and it is the grade most people mean when they ask for stainless steel without thinking further. Grade 316 becomes the safer choice for salt air, a swimming pool, or regular contact with chlorides (salts such as those in sea spray and pool water). On the day they are installed, the two grades can look identical, but they do not stay that way.

Duplex 2205 is a grade for marine sites, not the default for every outdoor stair. Specifying it "to be safe" on a dry city balcony adds cost without improving the finish. When duplex is worth the extra cost is explained in Stainless steel for marine and coastal environments. Use that article when the site really is coastal, and not as a substitute for describing the site.

Brown marks on exposed grade 304 are often tea staining (a light brown stain on the surface) rather than a failure of the metal. They still show, and on a minimalist design they are the whole complaint. So tell us how the piece will actually be cleaned, and choose a grade and finish that suit that cleaning, not a cleaning routine that will never happen. Tell us too whether the setting is indoor, exterior or coastal. "Outdoor" on its own is not enough, because a covered walkway and a rail facing the sea are both outdoors, and they are different jobs.

Approve a sample before the run, and confirm the sizes

For a repeated screen, handrail or panel, ask for a sample or first piece before the batch is made. A hidden bracket can be accepted by checking its dimensions, but a visible run cannot. So the sample is where the grain, the weld dressing and the choice between a brushed and a mirror finish are agreed. At that stage a correction affects only one piece, and the batch then copies what you approved rather than a new reading of the drawing.

When you approve the sample, check the things a person will see:

• the direction of the brushed grain
• the dressed welds and joints
• the ends of the rail
• the way two panels meet

That approval is for appearance, not a structural sign-off. We are asking you to judge the finish, and the structural engineer is still responsible for the loads.

Tell us what "approved" allows us to do next. It is normal for a sample to be agreed for appearance while the sizes are still waiting for a site measurement. But if that sample is quietly treated as the release for fifty panels, the approved finish gets copied onto the wrong dimensions. The architecture page already says a sample can be made before a full run. Use that option when the finish is the product. For a one-off bracket that nobody will see, skip it, or you will wait for an approval the job does not need.

Site sizes are often the larger gap. A stair drawn at design stage and the opening that was actually built are different objects, so tell us whether to fabricate to the issued drawing or to measured sizes. If you do not know yet, send the drawing and tell us that the site sizes may still change. We would rather wait than cut a handrail that cannot be installed.

If the rail is curved, read Bending stainless steel without cracking. Send the grade and the wall thickness with the radius, because the radius alone does not show whether the tube will flatten in the bend.

On visible work, the finish is part of the drawing. If it is not written down, someone else will decide it.