How to Resurface Concrete Steps

The riser rule a resurfacer can break

The IRC's stair rules apply to exterior entry steps as well as to stairs inside, and section R311.7.5.1 sets two limits on risers, quoted here from Placer County's handout on the California version:

• The riser "shall be measured vertically between leading edges of the adjacent treads."
• "The greatest riser height within any flight of stairs shall not exceed the smallest by more than" 3/8 inch.

The maximum riser is 7 3/4 inches in the model code. The section also says dimensions are measured "exclusive of carpets, rugs or runners," and nothing else, so a bonded layer of cement is part of the step for this purpose. That last point is our reading; we found no official commentary on toppings.

Now follow a layer of thickness t up the steps. Every tread rises by t, so the risers in the middle of the flight do not change. The bottom riser, from the walk to the first tread, grows by t, because the walk does not rise. The top riser, from the last tread to the landing, shrinks by t unless you resurface the landing too.

That arithmetic is ours, from the code's own measuring rule, and it assumes your risers are even now. Many old steps are not, so measure each riser before you buy. A bottom step that is already 7 1/2 inches goes over the 7 3/4 inch maximum with anything thicker than 1/4 inch. The fixes are to keep the layer thin, to resurface the landing as well, or to raise the walk at the foot of the steps by the same amount.

Is a cosmetic resurface something an inspector would ever see? Probably not, and some cities do not require a permit for it. But the rule exists because an odd-height step is a trip hazard, and that is true whether anyone checks or not. Minneapolis, for one, requires a permit to "alter, or replace exterior landings at doors and stairways."

Rebuild broken edges first

Quikrete's step repair instructions note that damage on concrete steps "usually occurs at the leading edges of the tread or at corners." A resurfacer will not rebuild a missing nosing. Quikrete's Re-Cap sheet says to repair broken edges with its Quick-Setting Cement first, and every repair source we read agrees on how to prepare the break.

• No feather edges. ACI's free repair guide RAP-6 says to sawcut the edges "to a depth of 1/2 in." to avoid feather edging, and to keep the cavity "generally square or rectangular in shape." Quikrete says to "Undercut and widen the broken area."
• Use a material made for vertical faces. A resurfacer sheet gives no build figure for a vertical face. Repair mortars do.
• Form the nosing. Quikrete: "Use forms for larger repairs or when the tread projects out from the riser." A board clamped to the riser face, flush with where the tread edge should be, gives you a straight nosing to work to.

From the Quick-Setting Cement sheet, Sakrete's broken edge guide and Top 'n Bond sheet, and the SikaQuick VOH sheet.

We looked for any authority that recommends pins or anchors in a nosing or corner repair and found none. The sources rely on a square, clean, sound-edged cavity and a material rated for the job.

How to resurface concrete steps

1. Measure every riser and decide your layer thickness from the table above.
2. Repair edges and corners with a vertical-rated mortar and let them cure.
3. Clean to bare concrete. Pressure wash, remove sealer or paint. Re-Cap goes "only to bare concrete."
4. Work top to bottom so you are never kneeling on fresh material, and dampen the concrete first so it is wet with no puddles.
5. Treads: spread the resurfacer to your thickness, no more than 1/4 inch per pass for Re-Cap, keeping a slight fall forward so water runs off. The IRC caps tread slope at 2 percent.
6. Riser faces: a thin coat troweled on, or leave them if they are sound. Keeping every riser face the same thickness keeps the tread depths equal.
7. Broom the treads when they are thumbprint hard, all strokes the same way, across the direction of travel.
8. Cure. Keep it damp for 24 to 48 hours, protect it from rain and frost, and keep everyone off for at least 8 hours with Re-Cap. Quikrete's Re-Cap Trowel Grade, the version whose sheet names steps, allows walking on it in 3 hours.

Put a temporary sign up and a second way in if you have one. Steps are the one surface people use without thinking.

What it costs

Steps take little material. Four risers 48 inches wide with 11 inch treads and 7 inch risers, plus a 4 by 4 foot landing, come to about 36 square feet. At 1/4 inch that is 3 bags of Re-Cap, about $111 at $36.97 a bag, plus a bag of repair mortar for the edges. Most of the job is the edge repair and the prep.

Replacing the same steps is a different scale of money, with demolition, forms and a footing. The concrete steps cost calculator prices new poured or precast steps, and the concrete steps guide covers building them.

When steps need replacing, not resurfacing

A 2000 HUD inspection guide puts the skeptical view bluntly: "Concrete cannot be repaired by resurfacing with a thin layer of more concrete," and "Deteriorated stairs should be repaired or replaced." That predates today's polymer resurfacers and was written about paving, but its point stands for steps that are failing rather than worn. Replace them if:

• They have settled or tipped, or pulled away from the house. The problem is the footing. Minneapolis, for example, requires stoop footings at least 42 inches below grade so frost cannot lift them.
• They are cracked through and the pieces move. Quikrete's sheet concedes that reflective cracking "cannot be completely prevented."
• Large sections are spalled deep on several steps, not just at the nosings.
• The risers are already uneven by close to 3/8 inch, so any layer pushes them over.

Precast steps are a special case. We found no manufacturer instructions for resurfacing them, and at least one precast maker's warranty requires its permission before any repair. If yours are under warranty, ask first.