Precast Concrete Steps: Sizes, Weights and Installation

Standard precast step sizes

There is no industry-standard size, but the stock range is consistent from plant to plant: 3 to 6 feet wide, one to six or seven risers, risers of 7 to 7-1/2 inches, and treads of about 11-1/2 to 12 inches. What varies most is the top platform, and that is the dimension that matters most.

One exception to watch for: some 3 foot units are made with 8 inch risers. Century Group lists 8 inch risers on its 36 inch wide steps, and Landis Block & Concrete stocks its 3 foot steps with an eight inch rise. That is over the IRC's 7-3/4 inch maximum for steps serving a house, so check the riser before you order a narrow unit for an entry door.

The platform is the trap. The residential code requires a landing at an exterior door that is at least 36 inches deep in the direction of travel and at least as wide as the door, under IRC R311.3 as reproduced by Indiana's building code office. A 24 or 30 inch stock platform does not meet that. Order a 42 or 48 inch platform for any step unit that serves as the landing at a door. The code does allow a stair of not more than two risers outside a door with no top landing, provided the door does not swing over the stairs, per Jefferson County, Colorado under the 2024 IRC, so a short set under an inswing door is the exception. Check with your building department.

The platform width should be at least the width of the door, and a step a foot or two wider than the door is easier to use with a storm door swinging out.

How to measure for precast steps

Measure from the finished walk or grade where the bottom step will sit, up to the top of the door threshold. Divide by the manufacturer's riser height and round to a whole number of risers. Then check where the top lands.

Say the threshold is 22 inches above the walk. Three risers at 7-1/4 inches is 21-3/4 inches, so the platform sits 1/4 inch below the threshold. Three at 7 inches puts it 1 inch below. Both work: IRC R311.3.1 allows the landing at the main exit door to be up to 1-1/2 inches below the top of the threshold. The bigger limit is the code's 7-3/4 inch maximum riser, which every 7 to 7-1/2 inch stock riser meets.

Two more measurements to take before ordering. The gap between the platform and the house: Wilbert Precast's measuring guide allows 1/2 inch maximum for accessibility and 1 inch as standard. And the bottom riser: the code wants every riser within 3/8 inch of the others, measured to the finished walk, so if the walk is sloped or settled the bottom step can come out short or tall. Fix the grade before the steps arrive.

A handrail is required at four or more risers under IRC R311.7.8. Some manufacturers, Hampton Concrete for one, cast in anchors for railings, so order them with the steps rather than drilling later.

How much precast steps weigh

Precast steps are hollow shells, open at the back on most sizes, which is why they are lighter than poured steps of the same size. Rainbow Concrete publishes the only full weight table we found, in kilograms. We converted it to pounds:

For comparison, a poured 4 foot set of three solid steps is close to a ton, per the stairs calculator. The platform is most of the weight in a precast unit: a 4 foot platform roughly doubles a three-riser set. Anything over a few hundred pounds is a boom truck job, not a two-person carry.

What precast steps sit on

This is where precast steps fail, and the manufacturers' own instructions differ more than you would expect:

• Blocks on compacted fill. Carey Precast: "Units should be installed with flat concrete blocks under each corner on compacted sand or gravel fill." Shea Concrete describes the same idea, with the weight carried by blocks under each corner, and notes that if the steps settle they can be lifted and reset.
• A gravel bed or concrete pad. Shea's delivery overview lists a bed of crushed stone, a concrete pad, or frost footings "if the situation requires." NuCast's installation manual warns that precast steps "are heavy and can sink into loose soil" and, for multi-step units, describes digging out 12 inches, placing 8 inches of compacted gravel and pouring a reinforced 4 inch pad.
• Frost footings. Some building departments require them. Minneapolis's exterior entry landing bulletin lists precast concrete stoops among typical construction, requires a permit to build or replace an exterior landing, and requires frost-depth footings for landings attached to a dwelling, with frost depth there at 42 inches.

The practical reading: a precast unit set on a well-compacted base and left free of the house can move a little with frost and be reset, which is why many manufacturers sell it that way. One that is anchored to the house or bridging a door threshold cannot move without damage, and that is the case where building departments ask for footings. Ask before you order. The gravel calculator sizes a stone base and the pad calculator sizes a slab under the steps.

Delivery, removal and the rotted sill

Precast steps arrive on a boom truck and are lifted into place. Shea describes its trucks as about 40 feet long and 13 feet 6 inches high, driving onto the driveway or lawn, and asks customers to check for overhead wires, low branches and the septic tank location before delivery. Shea's terms put any damage to the driveway or lawn on the homeowner.

Old precast steps can often be lifted out as one piece. Old poured steps have to be broken up. Either way, Shea warns that removing old steps "may reveal a rotted wooden sill," because water has been running behind the steps into the framing for years. Budget for that and look before the new steps go on. New concrete steps also need to sit below the siding: IRC R317.1 requires siding and framing within 2 inches of concrete steps or a porch slab to be treated or protected, as Middleton, Idaho's code determination explains.

How strong they are, and how to keep them that way

Precast steps are typically cast from 5,000 psi concrete. Steps Plus specifies "5000 psi air-entrained concrete" and Keeler Vault publishes 5,000 psi at 28 days with 5.5 percent air. That is well above the 3,000 to 3,500 psi the residential code asks of poured steps in cold climates, and it is the main durability argument for precast.

The care instructions are short and unanimous. Shea's price list says "DO NOT use salt or deicing products on stairs," Century Group and NuCast say the same, and both recommend resealing once a year. Use sand for traction instead of salt.

Precast or poured

Precast wins on speed, strength and usually price for a standard set: a three-riser, 4 foot unit lists in the hundreds, not thousands. What concrete steps cost has a real manufacturer price list and the comparison with poured steps. Poured wins when the shape is not standard: wraparound steps, a curve, an odd height that stock risers will not divide into, or a landing wider than the plant makes. Most plants will make custom sizes to order, at a price.

If you are pouring instead, start with how to build concrete steps. If you want a block-and-cap build, see cinder block steps.