I spent eleven years on scaffolds before I moved into estimating, and the argument I still have most often with owners starts the same way: someone repointed a 1920s building with a bagged Type S mortar, it looked sharp for four winters, and now the brick faces are shelling off in dinner-plate flakes while the joints sit there untouched. The mortar won. That is the whole problem in one sentence.
What the two mortars are actually doing
Mortar in an old solid-masonry wall is not glue. It is the part of the wall that is supposed to move, absorb water, and fail first. Pre-war New York brick — especially the softer common brick behind the face on Upper West Side buildings — was fired at lower and less consistent temperatures than modern extruded brick. Compressive strength on that common brick can run anywhere from 1,200 to 3,000 psi, and the original lime or lime-cement mortar was deliberately weaker than the units it bedded.
A bagged Type S mix lands around 1,800 psi and keeps climbing for years. Put that against a soft brick and the hierarchy is inverted. Water still gets in — it always does — and when it freezes it has to expand somewhere. If the joint is harder than the brick, the brick face spalls. If the joint is softer, the joint crumbles, which is a $30-a-square-foot problem instead of a $60-a-square-foot one, and nobody loses original material.
Reading the wall before anyone picks a mix
The mix should come from the wall, not from a spec sheet. Three things settle it:
- Scratch the existing joint. If a key or a screwdriver furrows it with light pressure, you are in lime or a very weak lime-cement. If it skates off, someone already got in there with Portland.
- Check the brick with the same key. If the brick scratches more easily than the joint, that wall is already telling you which repair failed.
- Look at exposure. A parapet, a chimney above the roofline, and a north-facing wall at grade all see different wetting and drying. It is normal for one elevation to need work while another has thirty years left.
On buildings over six stories the whole conversation gets folded into the facade inspection cycle, and the report drives the scope whether you like it or not. That is worth knowing before you budget, because a critical-condition finding puts a sidewalk shed up and sheds run $60 to $120 per linear foot per month while you sort the work out.
What repointing actually costs
On a pre-war building in Manhattan or the outer boroughs, expect roughly:
- $18 to $35 per square foot of wall for cut-and-point at pipe scaffold height, assuming 100 percent of joints get done.
- $40 to $75 per square foot where access is by suspended scaffold or swing stage, which is most upper-floor work.
- $900 to $2,500 per opening to reset a sill or rebuild a jamb return that has gone soft.
Access is usually more than half the number. That is why a $40,000 job and a $180,000 job can involve the same amount of trowel time.
Where the work goes wrong
Four things, in the order I see them:
- Grinding with an angle grinder on a running bed joint. It is fast, it overcuts head joints, and it takes the arris off the brick. Joints should be raked to two and a half times their width — usually 5/8 to 3/4 inch — with a chisel or a properly guided saw, not freehand.
- Pointing wet or pointing dry. The joint should be damp, not saturated. Mortar packed into a bone-dry joint on a July afternoon loses its water to the brick before it can cure and turns to sand by spring.
- One mix for the whole building. A parapet takes a harder mix than a sheltered courtyard wall. Crews hate mixing two batches. It matters.
None of this is exotic, but it is the difference between a repair that lasts eighty years and one that hands the next owner a spalled facade. On pre-war stock I would rather see a crew that spends two days on mockups and mix trials than one that shows up Monday with forty bags of Type S — and for parapet and cornice work specifically, that usually means bringing in a New York facade repair contractor who does probes and mockups as a matter of course rather than a general mason with a scaffold license.
Frequently asked questions
How do I know if my building has lime mortar? Scratch a joint in a sheltered spot with a key. Lime and weak lime-cement furrow under light pressure and the dust is pale and chalky; Portland resists the key and dusts gray. If the building went up before about 1920 and has not been repointed, lime is the safe assumption until a lab says otherwise.
Can I mix lime and Portland? Yes, and most repair mortars do. A Type O mix — roughly 1 part Portland, 2 parts lime, 9 parts sand — lands near 350 psi and suits most soft pre-war brick. The mistake is not using Portland at all, it is using too much of it.
How long should repointing last? A correctly specified and tooled job on a wall with working flashings and gutters should run 50 to 100 years. If a repointing job is failing in under 15, the failure is almost always the mix, the joint prep, or water getting in from above — not the mason’s speed.