Is it the brick or the mortar?
Look at where material is missing. Recessed or sandy joints are a mortar problem. Shallow pits, chips or thin peeling layers across the brick faces are a brick problem. The two often show up together, but repointing the joints does not bring back a lost brick face. A white, powdery crust on the surface is usually salt deposits rather than brick loss; see how efflorescence differs from mold on masonry.
One pattern points straight at the mortar. If the joints look sound and sharp while the bricks around them are eroding, the joints may have been repointed with a hard, cement-rich mortar. The Park Service's Common Problems with Brick Masonry notes that hard mortars are less permeable than the brick and move differently, so the brick wears away first.
Read the damage pattern from the ground
Photograph the area, then zoom in. Note whether the worst damage sits under a gutter, a downspout, a window sill, a roof edge or a parapet. Near the base of the wall, look for downspouts dumping water at the foundation, low soil, sprinklers hitting the brick, or a spot that stays dark after the rest of the wall dries. Fresh flakes on the ground after a freeze mean it is active.
Park Service Preservation Brief 39 lists faulty roofs and gutters among the most common sources of unwanted moisture in old buildings. On a Philadelphia rowhome, damage high on the front or rear wall often traces back to the roof drain, scupper or parapet; flat-roof drainage on rowhomes is worth checking first. Don't climb up or pry at loose faces to look. Fixing brick while a gutter keeps soaking it just resets the clock.
Why harder mortar can hurt old brick
Park Service Preservation Brief 2 and Brief 47 call for repointing mortar that is slightly weaker than the masonry around it, so the joint, not the brick, takes the wear. Brief 2 notes that buildings put up between 1873 and 1930 used a wide range of mortars, from straight lime and sand to mixes with some portland cement, and by the 1930s most masons used a mix of equal parts portland cement and lime.
So ask the mason how the new mortar was chosen for your brick and the original mortar, not just for color. Brief 2 also says old mortar should be raked out to a depth of 2 to 2½ times the joint width, and it recommends test panels so you can approve the mortar and workmanship on a small area before the whole wall is done.
Don't sandblast, pressure-wash or seal it
The Park Service says abrasive cleaning such as sandblasting strips the hard outer skin of the brick and exposes the softer core, which then weathers quickly. High-pressure washing can do similar harm. Preservation Brief 1 also warns against assuming a waterproof coating or clear sealer will stop spalling: a coating can trap water that enters from elsewhere, and when that water freezes the damage gets worse. If someone proposes a coating, ask what problem it fixes and how the wall will dry.
Philadelphia historic properties need review first
If the house is on the Philadelphia Register of Historic Places, either on its own or inside a historic district, the city says masonry cleaning, painting, pointing, repair and replacement all need Historical Commission project review, usually as part of the building permit application. Review is free, and the city says staff approve more than 90% of applications without sending them to the full commission. Check whether your property is designated before you sign a contract, and make sure your contractor knows.
When to call a mason and when to call an engineer
Call a mason who works on older brick when faces keep shedding, the damage is spreading or many bricks are affected. Ask them to assess both bricks and joints, not just price repointing. Bricks with deep loss can often be cut out and replaced with salvaged brick that matches.
Bowing or leaning walls, bulges, displaced brick, or cracks that run around windows and doors call for a structural engineer who knows masonry. The Park Service notes that sagging or rusting lintels over openings commonly cause this kind of cracking. If pieces are falling or the wall looks unstable, keep people away from it and get it assessed right away.
What to ask before you approve the work
- What is causing the damage, and what is the evidence?
- What water source has to be fixed first, and by which trade (roofer, gutter installer, mason)?
- Which bricks will be replaced, and where will matching brick come from?
- How was the mortar selected for strength and permeability, not only color, and will you do a test panel?
- Does this house need Historical Commission review or a permit for this work?
- Will the written scope separate drainage fixes, brick replacement and joint work?