Signs you need this
- Mortar between basement stones can be scraped out with a fingernail
- Sand and grit collecting along the base of the basement wall
- A stone has shifted, dropped or rotated out of line
- Water running in at a specific point after heavy rain
- A porch pier or column base is leaning, cracked or crushed at the top
- Efflorescence or flaking paint across the inside of the foundation wall
What is actually holding your house up
Walk into a basement in Shaw, Soulard or Old North and you will usually find a rubble limestone wall: irregular blocks of local limestone, laid up in wide lime mortar joints, sometimes with a brick course near the top where the wall meets the floor framing. Limestone was quarried here in quantity and it was cheaper than brick below grade. Those walls have held for well over a century, and the stone is rarely the problem. The mortar is.
Lime mortar in a damp basement gives up slowly. It washes, it powders, and eventually you have a joint that is open several inches behind the face with nothing in it. You can see the result as a small cone of sand at the base of the wall. Repointing catches this while the stones are still bearing on each other. Left long enough, stones start to shift and the repair becomes a rebuild.
Water first, mortar second
Almost every wet basement in this city starts above ground. A downspout discharging at the wall, soil graded toward the house after decades of mulch, a cracked concrete areaway beside the kitchen door, a window well with no drain, or a gangway between two flats that funnels the whole roof of both buildings into a six foot strip. We walk the outside before we price the inside, and we will tell you when the fix is a $200 downspout extension rather than a masonry scope.
We also look at what previous owners applied. Tar, cement parge, waterproof paint and plastic panels all get used on these walls. They rarely stop the water, and they usually move it. The test patch we open tells us whether the coating is holding sound mortar behind it or hiding a wall that has been quietly washing out for twenty years.
Piers, areaways and garden walls
Above grade, the stone work that fails first on a St. Louis property is rarely the house. It is the porch piers, the areaway walls beside a basement entry, the stone retaining wall at the sidewalk, and the low garden wall. All of them are exposed on more than one face, all of them sit in wet ground, and none of them have a roof.
The expansive clay soil across much of St. Louis County makes this worse in Kirkwood and Webster Groves, where it swells in a wet spring and shrinks in an August drought. Porch piers on shallow bases move with it, the porch above racks, and the brick cracks in a stair step pattern. Rebuilding the pier without addressing what it sits on gets you the same crack in five years, so we look at the base and the drainage around it before quoting.
What a written scope gives you here
Foundation work is easy to sell badly, because most of it is out of sight. Our estimate names each wall, the square footage, the depth we are raking to, the mortar we are using, and the photographs we took of the test area. You get the photos whether or not you hire us, which means you can take them to another mason and compare like for like.
How the work runs
- 1
Look behind the coating
Most basements here have been parged, painted or covered at some point. We open a test area to see the actual stone and mortar, because a waterproof coating hides the condition underneath rather than fixing it.
- 2
Trace where the water starts
Foundation water usually starts above ground: a downspout at the wall, negative grade, a cracked areaway, a failed window well. We check outside before recommending anything inside.
- 3
Repoint in lime, from the bottom up
Joints are raked back to sound material, flushed, dampened and packed in lifts with a lime mortar that breathes. Deep voids behind the face are filled before the face joints go in.
- 4
Reset, pin or rebuild what has moved
Stones that have dropped out of line are lifted and reset on a full bed. Piers that are crushed or leaning come down and go back up on a sound base.
What it typically costs
| Job | Typical range |
|---|---|
| Interior foundation repointing, per sq ft Rubble limestone raked, flushed and pointed in lime mortar. Access and headroom move the price | $18 to $40 per sq ft |
| Porch pier rebuild Per pier, taken down and rebuilt. Shoring the porch above is included | $900 to $3,000 |
| Reset a displaced stone Lifted, cleaned, re-bedded and pointed. Price rises when the wall above needs shoring | $350 to $1,100 |
| Retaining wall repointing Garden and areaway walls. Drainage behind the wall is quoted separately | $35 to $75 per linear ft |
| Retaining wall rebuild Taken down, drainage added behind, rebuilt with the original stone where it is sound | $180 to $420 per linear ft |
| Areaway or stair well repair The sunken entry beside a flat. Usually the wettest masonry at ground level | $1,200 to $5,000 |
Typical ranges for St. Louis and the surrounding area , reviewed September 2026. Every quote is written and fixed before work starts.