Why Block Walls Are Different
My house has poured concrete walls. One solid piece. My parents' house has walls made of individual blocks held together with mortar. That difference matters a lot when it comes to cracks.
The Mortar Is the Weak Link
The blocks themselves are pretty tough. Drop one on your foot and you'll believe me. But the mortar between them? That's where cracks happen.
In my poured walls, a crack just goes straight through the concrete wherever it wants. In my parents' block walls, cracks follow the mortar joints because that's the path of least resistance. It creates those distinctive stair-step patterns.
The Hollow Core Question
This part surprised me. Those blocks have hollow cores. In newer construction, they're supposed to fill those cores with concrete and rebar. Makes the wall way stronger.
My parents' walls? Built in 1962. Nobody filled the cores. They're basically stacked hollow blocks with mortar. The contractor who eventually looked at them said this is super common in older homes. The walls work fine until they don't.
What We Found in My Parents' Basement
When I actually looked closely, there was more going on than the one crack my dad had noticed.
The Stair-Step Cracks
The main cracks followed the mortar joints in a zigzag pattern. Up, over, up, over. Like climbing stairs. They ran from one corner toward a basement window.
I later learned this usually means settlement. Part of the foundation is dropping relative to the rest, and the wall cracks along the mortar to accommodate the movement.
The Crumbly Mortar
When I poked at the mortar with my pocket knife, some of it just fell out. Not everywhere, but in spots. My mom said it had been like that "forever."
Turns out 60-year-old mortar doesn't hold up the way it used to. It gets sandy and weak over time. Doesn't mean the wall is failing, but it does mean the mortar isn't doing its job as well as it once did.
The Slightly Inward Wall
This was the concerning part. When I held a level against the wall, I could see it wasn't perfectly straight anymore. Maybe half an inch to an inch of bow in one section. My dad had never noticed because it happened so slowly.
The soil outside had been pushing on that wall for 60 years. Eventually it started winning.
What the Contractor Said
My parents got a structural engineer first (my insistence) and then a foundation contractor. Total cost for opinions: about $400 between them.
Not an Emergency
Good news first. The engineer said the wall wasn't in danger of failing tomorrow. The movement had been gradual over decades. The house wasn't going to collapse.
But he recommended doing something before it got worse. Another decade of doing nothing could turn a $6,000 fix into a $15,000 fix.
The Recommended Fix
Carbon fiber straps. Basically these thin black strips that get epoxied vertically to the wall. They prevent the wall from bowing any further. Can't straighten it back, but can stop the progression.
The quote: $5,800 for six straps plus some repointing of the worst mortar joints.
The Drainage Lecture
Both the engineer and the contractor mentioned drainage. The downspouts on that side of the house emptied right at the foundation. All that water soaked into the clay soil and expanded, pushing harder on the wall.
My dad spent $150 on downspout extensions the next weekend. Should have done it 30 years ago.
Checking Your Own Block Foundation
After going through this with my parents, I have a better sense of what to look for in block walls.
Look at the Mortar
Is it solid, or can you scrape it out with your fingernail? Old mortar gets soft. If it's crumbling in places, that's not necessarily a crisis, but it's worth noting.
Follow the Crack Patterns
Stair-step cracks following mortar joints are the classic sign of settlement or lateral pressure. A few small ones at corners might be nothing. Long cracks that run most of a wall deserve attention.
Check for Bow
Hold something straight against the wall. A level, a 2x4, anything long and flat. If you can see a gap in the middle, the wall is bowing. Half an inch might be old and stable. An inch or more needs someone to look at it.
Look for Block Damage
Are the faces of the blocks themselves flaking or crumbling? That's called spalling. Usually from water getting in and freeze-thaw cycles breaking the surface apart. Minor spalling is cosmetic. Severe spalling is a durability problem.
Consider the Age
If your house is 50+ years old with a block foundation, it's lived through a lot. Doesn't mean something is wrong, but it's worth an annual walk-through to see if anything is changing.
My parents did this walk-through zero times in 60 years. Don't be like my parents.