A brick step is walked on, holds water on a flat surface, and meets the ground at its base. That combination sets the selection: a brick rated for severe weather and foot traffic, and a mortar suited to horizontal, ground-contact work. A brick chosen only for its colour, or a mortar chosen only for its strength, can fail a step long before it fails a wall.
Which brick should a step tread use?
Use a brick made for paving, or a facing brick rated for severe exterior weathering. A paving brick under ASTM C902 is made for pedestrian and light traffic paving. A facing brick under ASTM C216 can serve a step only when its grade matches the weather the step will face, which the next section covers.
Check the manufacturer's stated use before anything else. A unit sold for an interior floor or a sheltered wall is not a step tread because it looks like one. The product sheet, not the display stack, decides whether the brick belongs on a step.
Write "C902 paving brick" or "C216 facing brick, Grade SW" on the selection record. A colour name alone cannot be checked later.
How do you match the brick to the weather?
Match the weathering class to the wettest, coldest condition the step will face. A step tread can sit saturated after rain, then freeze overnight. That is the severe case, and the class must cover it.
| Standard and class | What it covers | Step reading |
|---|---|---|
| C902 Class SX | Brick that may be frozen while saturated with water | The default for an exterior step where freezing is possible. When no class is specified, C902 makes SX govern. |
| C902 Class MX | Exterior use where resistance to freezing is not a factor | An exterior step in a climate without freezing, recorded with that climate reason. |
| C902 Class NX | Not intended for exterior use | Never an exterior step. Interior use only. |
| C216 Grade SW | Severe weathering for facing brick | The facing-brick route for an exterior step in severe weather. |
| C216 Grade MW | Moderate weathering for facing brick | The facing-brick route only where the weather is moderate and the record says so. |
For C216 facing brick, Grade SW carries an average compressive strength of 3000 psi, a maximum boiling absorption of 17.0 percent, and a maximum saturation coefficient of 0.78. Grade MW carries 2500 psi, 22.0 percent, and 0.88. Those figures describe the grade. They do not, on their own, approve a product for a step. The class, the stated use, and the project specification approve it together.
How do you match the brick to the traffic on the tread?
Match the abrasion type to the foot traffic the tread will carry. Paving brick is used horizontally and exposed to traffic, so ASTM C902 assigns it a traffic type as well as a weathering class.
| C902 type | Traffic it covers | Step reading |
|---|---|---|
| Type I | Extensive abrasion | A public entry, a shopfront step, or any step that carries constant public traffic. |
| Type II | Intermediate abrasion | An ordinary home entry step and an exterior walkway step. |
| Type III | Low abrasion | A light-traffic home patio or floor, not a busy entry step. |
Wear concentrates on the tread nosing, the front edge of each step. A type chosen for a flat patio can still be wrong for an entry step that takes the same feet on a narrow edge, day after day. Record the traffic reason beside the type, so a later substitution cannot quietly downgrade it.
Which size and joint should the selection record first?
Choose the brick size and the joint width before measuring, because both set the coursing the measuring page counts. A modular brick is nominally 4 by 2-2/3 by 8 in, and a standard brick is 3-5/8 by 2-1/4 by 8 in, each at a 3/8 in joint under the Brick Industry Association coverage figures. The measuring page turns face area into a brick count at one size and one joint. Change either after measuring, and the count must be redone.
Record the nominal size, the actual size, and the joint width as three separate lines. A nominal size without its joint width cannot be checked, and a coverage rate cannot be carried to another size or joint. The brick sizes and coverage chart holds the named size rows and their estimating conditions, and the measuring guide for brick steps shows how the chosen size and joint enter the count.
Which mortar type should brick steps use?
Start from the project specification. Where no specification names a mortar, Type S is the usual starting point for an exterior step flight. The ASTM C270 selection guide puts pavements, walks, and patios in exterior at-or-below-grade work, and it flags masonry in a nominally horizontal surface as extremely vulnerable to weathering, with its mortar selected with due caution. A step flight is horizontal, walked on, and grounded at its base, so it sits in that cautious group.
| Mortar type | 28-day strength | Step reading |
|---|---|---|
| Type M | 2500 psi minimum average | Only where a specification or a heavy-load condition requires it. Strength alone is not a reason to pick it. |
| Type S | 1800 psi minimum average | The usual starting point for an exterior step flight with no specification, and the at-or-below-grade choice in the C270 guide. |
| Type N | 750 psi minimum average | The general above-grade mortar. It fits a step only when the project record supports it for that step. |
| Type O | 350 psi minimum average | Not for an exterior step. Interior, non-weathering work only, and never where masonry is likely to be frozen while saturated. |
Do not pick the strongest mortar by default. Mortar harder than the brick can damage the brick first, spalling the units while the joints stay intact. The mortar and the brick are chosen as a pair, and the pair is checked against the manufacturer's guidance before ordering.
Record whether the mortar follows the proportion specification or the property specification. The Brick Industry Association notes that the proportion specification is the typical route. Either route must be named on the record, because a type letter alone does not say how the mortar was specified.
What goes into the mortar?
Three ingredients need a line each on the record: sand, water, and colour. Sand follows ASTM C144. Water must be potable. Pigment, where used, is limited to 10 percent metallic oxide and 2 percent carbon black by cement weight, halved for masonry cement and mortar cement.
Judge colour from a dry sample, laid as a short course in daylight, not from a screen photo or a wet mix. Mortar colour is part of the selection, and a sample course shows the brick and the joint together, which is how the finished step will read. Approve the sample in writing before ordering, and keep one sample brick and one joint sample with the record.
A complete selection record
One selection record, checked before measuring, prevents most substitutions. The example below shows one complete record for a home entry in a freezing climate. It is an example, not a rule for every step. Change the climate, the traffic, or the specification, and the record changes with it.
| Line | Example entry | Check |
|---|---|---|
| Brick standard and class | C902 paving brick, Class SX | Frozen while saturated is covered |
| Traffic type | Type II | Ordinary home entry traffic |
| Size and joint | Modular, 3/8 in joint | Matches the measuring count |
| Mortar type and route | Type S, proportion specification | Horizontal, at-or-below-grade work |
| Sand and water | ASTM C144 sand, potable water | Named on the supplier record |
| Colour | Dry sample course approved in daylight | Sample kept with the record |
| Project control | No conflicting specification found | Specification checked before ordering |
Use the Brick Calculator once the selection record is set, and return to the Brick Calculators hub for the related brick tools.
Selection mistakes that cost a step
- Using an interior NX brick on an exterior step because its colour matched.
- Putting a Type III light-traffic brick on a busy public entry step.
- Using a smooth glazed wall face as a tread without checking its stated use.
- Choosing Type O mortar for an exterior step, or Type M mortar for strength alone.
- Picking a mortar harder than the brick, so the brick spalls first.
- Judging mortar colour from a screen photo instead of a dry sample course.
- Choosing the brick size after measuring, which invalidates the count.
- Recording a colour name without the standard, class, type, size, joint, and mortar type.
Safety and professional scope
Brick and mortar selection does not set the step geometry, the foundation, the drainage, the handrail, or the load path. Those decisions follow the project drawings, the applicable code, the site conditions, and the responsible qualified people. A selection record keeps the material choice checkable. It does not replace a specification, a structural check, or a site inspection.
Handle mortar materials with the supplier's safety guidance, keep dust and wet mortar off skin and eyes as the product sheet directs, and wash tools and hands after laying. Store brick and bagged mortar dry, off the ground, and covered until use.
Sources and scope
- ASTM C902, Standard Specification for Pedestrian and Light Traffic Paving Brick: paving brick scope, weathering classes SX, MX, and NX, traffic types I, II, and III, and the SX default when no class is specified. Accessed 2026-10-26.
- Brick Industry Association, Technical Note 10, Dimensioning and Estimating Brick Masonry, February 2009: modular and standard brick sizes, 3/8 in joint, coverage rates, bond basis, and estimating limits. Accessed 2026-10-26.
- Brick Industry Association, Technical Note 8, Mortars for Brickwork, March 2020: mortar complying with ASTM C270, proportion specification as the typical route, ASTM C144 sand, potable water, and pigment limits. Accessed 2026-10-26.
- ASTM C270, Standard Specification for Mortar for Unit Masonry: property-specification minimum average 28-day strengths M 2500 psi, S 1800 psi, N 750 psi, O 350 psi, and the selection guide for horizontal and at-or-below-grade masonry. Accessed 2026-10-26.
- ASTM C216, Standard Specification for Facing Brick: Grade SW and Grade MW weathering grades and their strength, absorption, and saturation figures, as verified on the sibling veneer page 2026-10-25.
- Construction Specifier, Keeping Mortar Compatible: mortar harder than the adjacent brick can spall the brick while the mortar stays intact. Accessed 2026-10-26.
Scope: the classes, types, sizes, strengths, and ingredient limits in this guide come from the standards and notes listed above. The governing project specification, the manufacturer's stated use for the chosen product, the site climate and traffic, and the responsible qualified people control the accepted selection for a given step. The selection record, the step reading of the mortar table, and the example record are editorial method, not standard requirements.
Review responsibility: Saleem Sial owns the published calculation, source, and editorial checks. Waseem Sial, External Reviewer and Engineer, remains listed for ongoing external review; no completed external-review date is claimed.
Next, use the measuring guide for brick steps once the selection record is approved, or return to the Brick Calculators hub.
