The Essential Tools
These are the tools I reach for every time I check my cracks.
Crack Gauge Cards
This is the single most useful purchase I made. A crack gauge card is a piece of clear plastic with lines of graduated widths printed on it. You hold it against the crack and find the line that matches. Mine has widths from hairline up to 1/2 inch.
I bought mine for $15 from an engineering supply site. Hardware stores sometimes carry them for a few bucks more. Either way, cheap. And way more accurate than trying to use a ruler.
I keep one in my wallet now. Sounds obsessive, but whenever I'm at someone else's house and they mention foundation worries, I can do a quick check. I've pulled it out at Gary's place, at Helen's, even at my uncle's house before his settlement problem got fixed.
A Good Flashlight
My basement is dark. Corners especially. A bright flashlight makes cracks visible that I'd miss otherwise. I use a 500-lumen LED that cost maybe $25. Overkill? Probably. But I can see everything.
Raking light helps too. Shine the flashlight along the wall at an angle instead of straight at it. Cracks pop out more when the light comes from the side.
A Tape Measure
For measuring crack length and marking measurement points. Any tape measure works. The one that's been in my kitchen drawer since I moved in is fine.
I use it to measure from a fixed point, like a corner, to my measurement location. That way I can find the same spot again even if my tape marker falls off.
Pencil and Notebook
Carpenter's pencil for marking crack ends on the wall. Regular notebook for recording measurements. Nothing fancy. The notebook lives in the same drawer as my flashlight. I've filled maybe ten pages in five years.
Tools Worth Adding
These aren't essential, but they've been useful.
Crack Monitors
These are two-piece plastic gauges you epoxy across a crack. One piece has crosshairs, the other has a grid. If the crack moves, the crosshairs shift on the grid and you can read exactly how much.
I installed three of these on my worst-looking cracks. Cost about $12 each. Took maybe ten minutes each to install. They've been there for four years now, reading exactly zero movement the whole time.
Gary installed the same kind when his wall was bowing. His showed movement within the first month. The monitors don't lie. They just sit there and report what the crack is doing.
Digital Calipers
I bought a $20 pair of digital calipers after the first year. They measure to hundredths of an inch. More precision than I need, honestly, but satisfying to use.
The trick with calipers is consistency. You have to measure in exactly the same spot every time. I mark my measurement points with tape. Without the marks, caliper measurements are useless because you're never measuring the same place twice.
A 4-Foot Level
Not for measuring cracks directly, but for checking if walls are plumb. I hold it vertically against each wall a few times a year. Any lean or bow would show up. My walls have been straight and plumb every time I've checked.
This was especially useful when I was worried about wall movement after reading about Gary's problem. My level confirmed my walls were fine. His showed his wall was out of plumb by almost two inches at the top.
Phone Camera
Already in your pocket. Put a ruler or something for scale in every photo. Same angle every time. Date your photos or organize them in dated folders. My phone has become a critical part of my monitoring system.
Tools I Tried and Stopped Using
Not everything marketed for foundation monitoring is worth it.
Feeler Gauges
These are thin metal strips mechanics use. The idea is you slide them into a crack to measure width. I tried this for a few months. Problem is, my cracks are vertical. You can't really slide a gauge into a vertical crack the same way you would a horizontal one. And on horizontal cracks, the crack gauge card works better anyway.
They're fine if you have them for car work already. Not worth buying just for foundation monitoring.
Optical Crack Microscopes
I found one online for $60. Engineers use them for precise measurements. I used it twice. It's sitting in a drawer now.
The problem is overkill. I don't need to know if a crack is 0.127 inches versus 0.131 inches. I need to know if it's getting bigger. A crack gauge card tells me that for $15. The microscope tells me the same thing for $60 while being harder to use.
Digital Crack Monitors
High-end versions of crack monitors that record data automatically and can send alerts. Saw one online for $300. Briefly tempted.
But for homeowner monitoring, this is ridiculous. I check my cracks four times a year. I don't need a sensor recording 24/7. The $12 manual monitors tell me everything I need to know.
Laser Levels
Thought I was being fancy buying a $40 laser level to check wall plumb. Turns out my $15 regular level does the same thing. The laser is in a drawer somewhere. I just use the regular level.
Using Tools Consistently
The tool matters less than how you use it.
Same Spot Every Time
I can't emphasize this enough. Mark your measurement spots. I use small pieces of blue painter's tape above each measurement point. Some of my tape markers are five years old now. Faded, but still there.
Without consistent measurement spots, your data is noise. A crack can be 1/8 inch at one point and 3/16 inch six inches away. If you measure different spots, you'll think it's changing when it's not.
Same Conditions
Temperature affects crack width slightly. I try to measure in similar conditions each time. Basement in winter versus basement in summer is different. I note the rough conditions in my notebook. "January, cold," or "July, warm." Helps interpret any small variations.
Write It Down Immediately
I used to think I'd remember measurements until I got upstairs. I was wrong. Now I bring my notebook into the basement and write down each measurement as I take it. Can't misremember what you wrote down on the spot.
Keep Tools Together
My monitoring kit lives in one kitchen drawer. Flashlight, crack gauge, notebook, pencil, tape measure. When it's time to check, I grab everything at once. No hunting around for tools means I actually do my quarterly checks instead of putting them off.
My Monitoring Kit
Here's exactly what I use after five years of refinement.
The $35 Kit
Crack gauge card, $15. Good flashlight, $20. That's the essentials. Add a tape measure and notebook you already have. This is all you need to start monitoring effectively.
The Full Setup
Crack gauge card, $15. Flashlight, $20. Digital calipers, $20. Three crack monitors, $36. Notebook and pencil, $5. Under $100 total, and I've been using the same tools for five years.
The crack monitors are optional. They're more for peace of mind than necessity. But I like having permanent, attached gauges on my most concerning cracks. Zero effort to check them. Just glance at the readout.
Skip the Fancy Stuff
Optical scopes, digital monitors, specialized software. None of it. For a homeowner checking cracks a few times a year, simple tools work perfectly. Save that money for the $350 engineer visit if you ever need one.
Helping Gary With Tools
When Gary's wall started bowing, I lent him my crack gauge and helped him install monitors.
His Horizontal Crack
His crack was different from mine. Horizontal, not vertical. Water seeping through. The crack gauge showed it starting at 3/16 inch. We marked the ends and installed a crack monitor right across the widest point.
What The Monitor Showed
Within two months, his monitor showed the crack widening. The crosshairs had shifted maybe 1/16 inch. Doesn't sound like much, but for a two-month period, it proved the crack was active.
If he'd been measuring with a ruler and guessing, he might not have caught that small but real change. The monitor made it undeniable.
Tools Can't Fix Problems
Tools tell you what's happening. They don't fix anything. Gary's monitors showed progressive failure. The fix was $8,400 in wall anchors. The tools just told him he needed that fix before his wall failed completely.