Temporary stairs: 5 limits to check before takeoff

Key takeaways

• Measure the rise and landing footprint before counting units.
• Check building height and stories before choosing the stairway count.
• Measure the angle and step consistency across the system.
• Identify bearing and anchor points, and confirm responsibility for the structural check.

Why measure before you count

Temporary stair access looks like a small line item until someone has to build it, inspect it, use it every day, and take it down. A stair unit comes with landings, handrails, anchors, and crew time spent working around it. If you count units before you know whether the layout meets the basic limits, you may end up pricing the wrong thing, or pricing the right thing with the wrong quantity.

This post covers five limits to measure first. It is not a full code review, and it does not replace the rules that apply where your job is. Most of the examples come from Washington's construction stair rule, plus one general Oregon rule about walking and working surfaces, because those are official pages with specific numbers. Your job is to find out which limits apply on your project, measure the building against them, and then count.

Use the list as a checklist for the site walk. Bring the drawings, a tape, a level, an angle finder, and a notebook, and record each measurement next to the limit it tests. The numbers you write down on site are the ones that will hold up when the bid is questioned.

1. Vertical rise and landing spacing

Start with the total vertical rise the access has to cover. Then check how often the stair needs a landing. Washington's rule for stairways that will not be a permanent part of the structure says they "must have landings of not less than 30 inches (76 cm) in the direction of travel and extend at least 22 inches (56 cm) in width at every 12 feet (3.7 m) or less of vertical rise." ( WAC 296-155-477)

A landing that is wide enough but too shallow along the path of travel does not satisfy the rule, and a landing that is deep but narrow does not either.

Here is the method for a sample building. Suppose the access must climb well over 12 feet. Divide the total rise by 12 feet and round up to a whole number of runs. The number of landings between the bottom and top is one fewer than the number of runs. Each landing needs to be measured against the size in the rule. If your drawings show fewer landings than the method gives, you have a short count, and the price is wrong by at least one landing.

Landings also affect direction. The rule speaks of the landing's size in the direction of travel, so a stair that turns at a landing has to fit the landing in the path the crew walks, not just the space the stair occupies on the plan. Check the turn on the plan and on the ground, then price any extra footprint the turn needs.

Measure the rise from finished floor to finished floor, not from the nominal height on the drawings. Slab thickness, deck build-up, and temporary platforms can change the number. A few inches on each level can add up over several floors, and it may push the count across a threshold in the third limit below.

Price each landing as its own item: materials, placement, fasteners, and the handrail or guardrail that goes with it if your contract requires one. Don't treat landings as free parts of the stair. Use the related guardrail bid checks when counting protection around elevated work.

2. Stair angle

The second limit is the angle of the stair. Washington's rule says: "You must install stairs between 30 degrees and 50 degrees from horizontal." ( WAC 296-155-477)

The same section has a separate sentence that reads: "The stair must be installed at an angle of 70 degrees or less." That is a second angle figure in the same section, and it is not the same as the 30 to 50 degree range. Don't assume one covers the other. Read the full section, and confirm with the authority having jurisdiction which requirement applies to your access unit.

To check the angle on a unit, take the horizontal run and the vertical rise, then compute the angle with the arctangent of rise divided by run. Measure both from the bottom of the stair to the top. If you have only a drawing, compute it from the drawing, then confirm on site.

Tread depth and riser height are part of the same check. A stair that meets the angle range can still have treads too shallow for a comfortable step, and the riser variation limit in the next section applies to those same steps. Measure both dimensions for every unit, not just the overall angle.

Angle changes the price in two ways. A shallower stair takes more horizontal space and more length, so it needs more material and more site area. A steeper stair may fit the footprint but fall outside the range, which can mean a different product or a different layout. Settle the angle before you pick a unit from a catalog, because a unit that looks right on a spec sheet may not fit the space.

3. Number of stairways

The third limit is how many stairways the building needs. Washington's rule says that "In all buildings or structures two or more stories or 24 feet or more in height or depth, you must install suitable permanent or temporary stairways." ( WAC 296-155-477) That sets the point at which a stair becomes required at all.

Once a building meets that threshold, the access and exit count matters. The same rule says: "You must provide a minimum of one stairway for access and exit for buildings and structures to 3 stories or 36 feet; if more than 3 stories or 36 feet, you must provide two or more stairways." ( WAC 296-155-477)

For estimating, this turns into a yes-or-no check at a few points. The rule names both stories and feet, so check both figures. A building of three stories that is taller than 36 feet is over the height figure, so you cannot rely on the story count alone.

Stories are not always the same as floors on a plan. A mezzanine, a partial level, or a split-level area can make the story count unclear. Write down how you counted, and ask the owner or the authority having jurisdiction to confirm the count before you price two stairways against one.

Treat the stairway count as a major line, not a detail. Moving from one stairway to two is not an extra step; it is a second complete unit, with its own landings, anchors, inspection, and crew time for installation and removal. Put the count on the bid as its own line so the owner or general contractor can see the reason for the price.

4. Riser and tread consistency

The fourth limit is how even the steps are. Washington's rule says: "Variations in riser height or tread depth must not be over 1/4-inch (0.6 cm) in any stairway system." ( WAC 296-155-477)

The limit is about variation, meaning how far one riser or tread differs from the rest. A stair can look neat from the bottom and still fail it if one step is taller than the others.

That limit covers the whole stairway system, not just one unit. If you chain several units to reach a higher level, or if the stair uses shims, adjustable feet, or separate sections, the variation can build up across the system. Each unit can look close to right and the system can still fail the tolerance.

For estimating, add a measurement step. Measure every riser and every tread on each unit where the supplier does not provide written dimensions, and check the joins between units. Also measure the total height of the system after it is set, which is not the rule but tells you how the stack came out. If the crew has to shim or re-level, that is labor you should plan for in the schedule and the price, not something to absorb at the end.

A tight tolerance is why this deserves a line of its own. Ask suppliers for the dimensions they will guarantee, and put in the bid whether you are relying on their numbers or your own measurements.

5. Structural strength of the stair and its supports

The fifth limit is structural. Oregon's administrative rules say: "The employer must determine if the walking/working surfaces on which its employees are to work have the strength and structural integrity to safely support employees." ( Oregon Secretary of State Administrative Rules, rule 437-003-1501)

For your estimate, that means you should not treat the surface a stair sits on, hangs from, or lands on as strong enough just because the drawing shows it.

Practical steps: identify each bearing point, where the stair rests on a slab, deck, platform, scaffold, or ground. Identify each anchor point, where the stair attaches to the building or to a temporary frame. Ask the supplier for load and anchor details for the specific unit, and ask whether the existing structure needs a check before the stair goes on it. If an engineer or a qualified person must sign off, price that time and the site visit as a separate line. If the structure cannot take the load, the answer may be a new footing, a bracing frame, or a different location, and each of those changes the cost.

Temporary stairs often sit on surfaces built for other purposes. Ask whether the surface was built for the loads the stair puts on it, and whether the design assumed a permanent load or a temporary one. Those are different answers, and the person who signs the structural check should know which applies.

Note in the bid that the structural check is a precondition, and that you did not verify the structure yourself unless you did.

Illustrative example: counting intermediate landings

That gives 2 intermediate landings between the bottom and top. Count those separately from any top or bottom landings the layout needs. Then check each landing's dimensions, the stair angle, step consistency, and supports before pricing the layout. This arithmetic counts landings for the assumed layout; confirm the required number of stairways separately from the building's height and stories.

Turn the five checks into a count

Build a one-page sheet covering total rise, landing count and size, angle, number of stairways, riser and tread variation, and structural check with the name of the person who signs off. Fill each item from drawings first, then from a site visit. Where drawings and site measurements disagree, use the site measurement and flag the difference.

Work through the items in order. Start with the rise and stairway count because they set how many units you need. Then check angle and riser variation on the unit you plan to use. The structural check comes last in this list, but it can change the layout, so raise it early with the supplier.

Once the sheet is complete, count what the sheet says, not what the first drawing suggested. Count each stairway unit, each landing, each handrail or guardrail the rule requires, each anchor, each shim or leveling kit, and the time to install, inspect, and remove. Then compare the count to the limits one more time. If a value fails, don't quietly adjust the number. Flag it, and show the owner what would change the count.

A useful habit: put the rule and the measurement on the bid next to each line. Lines like "landings: counted from total rise and maximum spacing" are easier to check than "landings: as needed." It also protects you if the layout changes later and someone asks why the price moved.

What to send with the bid

A short assumptions list protects both sides. Include the building height in stories and feet, the number of stairways you priced and why, the landing count and spacing, the angle range you designed to, the riser and tread tolerance you relied on, and the name of the person responsible for the structural check. If any item is still open, say so in the bid and state the price assumption behind it.

That list also helps when the general contractor changes the schedule or the layout. You can point to the assumption that changed, not argue about the whole price. Use the construction estimate audit for the wider bid review.

Common mistakes

Estimators tend to miss the same few things. Watch for these:

• Counting one stairway when the building crosses the story or height line for a second one.
• Using nominal floor heights instead of measured floor-to-floor heights.
• Pricing landings as if they were part of the stair.
• Accepting a catalog angle without measuring the space.
• Checking one unit's steps but not the whole system's variation.
• Assuming the structure can carry the stair because the drawing shows a slab.

Each one is a small check at the start, and each one is an expensive fix at the end.

Limits of this list

These five limits are a starting point, not a full list. Guardrails, handrails, lighting, clearances, and inspection requirements can all apply, and this post does not go through them. The Washington and Oregon rules quoted here are examples of what official pages say; they may not apply to your state, province, or country. Confirm the requirements that apply to your project with the authority having jurisdiction and with the site safety lead before you finalize a price.

Today, mark the rise, landing locations, and unresolved measurements on your drawings, then arrange the site walk before counting units.

Common questions

Can I count from drawings alone?

Confirm drawing measurements on site before finalizing the count. Flag differences and show which measurements your bid uses.

Does checking the stair angle cover step consistency?

Check step consistency separately from the overall angle. Measure the risers, treads, and joins across the stairway system.

What should I do when a structural check is still open?

State the open check and its price assumption in the bid. Identify who is responsible before treating the layout as settled.