Metal stairs are installed by setting the fabricated stair in place, fastening the top to the floor structure and the bottom to the slab or footing with the connections shown on the shop drawings, then checking level, plumb and every riser before treads and railings are finished. Most of the work happens before the stair arrives: the opening, supports and finished floor heights have to be right, because a steel stair is built to the site and doesn't trim like wood.
This guide explains the installation process so you know what to prepare and what to expect. A stair is a structural element with code requirements, so the connections should come from the stair's designer or fabricator, and the work is normally part of a building permit.
Before the stair arrives
A smooth install is mostly preparation:
- The opening is framed and final. Header, trimmers and any landing framing are built to the drawings. The fabricator measured the opening; if it has changed since, tell them before the stair ships.
- Finished floor heights are confirmed. The top and bottom risers depend on the finished floor at each end. If you have changed from carpet to tile, or added a concrete topping, the first or last riser will be off. Our article on Ontario Building Code rules for steel stairs explains the tolerances.
- Supports are ready. The beam, header, ledger, slab or footing the stair connects to must be in place and able to take the load. Concrete should be cured enough for anchors.
- The access route is clear. Measure doors, hallways, turns and stairwells against the largest piece. Plan who carries it and how.
- The permit is in hand if the work needs one.
Getting the stair into place
Steel stairs are heavy. A straight residential stair frame is a multi-person lift; long stairs, stair towers and stairs with landings need lifting equipment.
How the stair is delivered depends on access:
- One piece: fastest to install, if it fits through the building.
- Sections bolted together on site: common for stairs with landings, long flights or tight access.
- Separate stringers and treads: the stringers are set and fastened, then treads are bolted or welded on. This suits finished homes where a whole stair won't fit through the door.
While positioning, the stair is supported temporarily (blocking, shores or a lift) so it never hangs from an unfinished connection. On construction sites, lifting and temporary support are planned like any other steel lift; our guide to steel erection safety in Ontario covers the site rules.
Top connections
The top of the stair carries a large share of its load into the floor structure. The connection depends on what it fastens to:
| Supporting structure | Typical connection | Points to check |
|---|---|---|
| Steel beam or channel header | Plates or angles on the stringers, bolted or welded to the steel | Bolt size and hole alignment match the shop drawings |
| Wood header or rim board | Angle or plate fastened with through-bolts or structural screws as detailed | The wood member must be designed to carry the stair; framing may need doubling or hangers |
| Concrete slab edge or wall | Plates fastened with anchors, or welded to embedded plates | Edge distance, embedment and anchor type from the designer and anchor manufacturer |
| Masonry wall | Anchors into solid or grouted block | Hollow block needs grouting or a different detail |
The installer sets the top first, at the height and position on the drawings, then checks the stair's slope and alignment before fastening the bottom.
Bottom connections and steel stairs on concrete
Most interior steel stairs land on a concrete slab. The bottom of each stringer usually has a base plate or angle.
The installation sequence, in outline:
- Set and align. The stair is brought to its final position, with the bottom plates on the slab and the top connection fitted.
- Level and shim. Slabs are rarely perfectly flat, so steel shims or non-shrink grout under the plates bring the stair level side to side and set the bottom riser height.
- Check what's in the slab. Before drilling, installers check for in-floor heating tubing, conduit, rebar and post-tensioning. Commercial jobs often scan the slab. Drilling into a radiant heating loop is an expensive mistake.
- Anchor. Holes are drilled to the anchor manufacturer's diameter and depth, cleaned, and the anchors installed and tightened or cured. Anchors need enough distance from slab edges and from each other.
- Tighten and recheck. All bolts are tightened, and the stair is checked again for level and plumb.
Exterior stairs usually land on concrete piers or a pad with footings below frost, and on base plates that keep the steel above grade and out of standing water. Our guide to exterior steel stairs covers foundations, drainage and finishes.
Installing steel stair stringers
When a stair arrives as separate stringers and treads:
- Set both stringers at the drawn width, with top and bottom connections fitted loosely.
- Check parallel and level. Measure the width at the top and bottom, check the stringers are level with each other along their length, and measure diagonals to make sure the frame is square.
- Fasten the connections once the geometry is right.
- Install treads on their supports, bolted or welded as detailed, working from the bottom up.
- Measure each riser and run as treads go on. The code allows only small variations between steps, so measure rather than eyeball.
For stringer sections and how they carry treads, see steel stair stringer sizes.
Railings, treads and final checks
After the frame is fastened:
- Railings and guards go on, bolted to tabs on the stringers or fixed to walls and floors. Handrail heights are measured from a line along the tread nosings. See how metal handrails are installed.
- Finished treads such as wood or stone are usually installed late in the job, so they don't get damaged. Protect steel treads with covers if other trades will use the stair.
- Touch-up any field welds, scratches and drilled holes in the finish.
Before calling for inspection or handing over, walk the stair and check:
- Every riser and run within tolerance, especially the top and bottom steps
- No bounce, rattle or sideways movement
- All bolts installed and tight, all anchors set
- Headroom over the full stair
- Handrails continuous and at the right height, guards in place where required
- Nosings free of sharp edges
Who does what
On most jobs:
- The designer or engineer sets the stair's layout and, where needed, designs the steel and connections.
- The general contractor builds the opening, the supports and the slab or footings.
- The fabricator measures, draws and builds the stair, and may install it or hand off to an installer.
- The building inspector checks the finished stair against the permit drawings and the code.
Clear responsibility for the top connection matters most. Agree up front who provides the header or embedded plate and who supplies the bolts and anchors.
Getting a steel stair made for your project
We fabricate custom steel stairs, railings, gates and ladders to your drawings, with in-house shop drawings, CWB certified shop welding and delivery across the GTA and Ontario. Installation is by your installer or contractor. Send your drawings or measurements for a quote, or see our fabrication services. For how the stair itself is built, read how steel stairs are fabricated.
Frequently asked questions
How are steel stairs attached to the floor above?
Usually by connection plates or angles at the top of the stringers, bolted to a steel beam, fastened to a designed wood header or rim, or anchored to concrete with embedded plates or anchors. The connection is detailed on the shop drawings to suit the structure it fastens to.
How do you install steel stairs on concrete?
The bottom of each stringer has a plate or angle that is set on the slab, shimmed or grouted level, and fastened with anchors rated for concrete. Installers check for in-floor heating, conduit and rebar before drilling and keep anchors back from slab edges.
Do you need a permit to install metal stairs?
New or replacement stairs are usually part of permitted work in Ontario, especially inside a house or where the stair changes the structure or exits. Check with your municipality's building department before you start.
Can steel stairs be installed in one piece?
Small stairs often can. Longer stairs, stairs with landings and stairs going into finished homes are usually delivered in sections or as separate stringers and treads, with bolted joints so they can be carried in and assembled without field welding.
Should wood treads go on before or after the stair is installed?
Usually after. The steel frame is set and fastened first, then finished treads are installed near the end of the job so they don't get damaged by other trades.
