Why Moisture Matters
Water causes more foundation problems than anything else.
What Gary Taught Me
Gary's horizontal crack wasn't just a crack. It was seeping water during rain. The soil behind his wall was saturated. The water pressure was literally pushing his wall in. The moisture was the cause. The crack was the symptom.
If Gary had fixed his drainage years ago, maybe his wall never would have bowed. By the time we were installing crack monitors, it was too late for prevention. He needed $8,400 in wall anchors.
Wet Soil Pressure
Dry soil doesn't push very hard against a wall. Saturated soil pushes much harder. Hydrostatic pressure from water-logged soil is what overcomes foundation walls. Keeping soil drier keeps pressure lower.
This is why drainage is so important. Every time I think about Gary's wall, I check my downspouts.
Freeze-Thaw Damage
Wet concrete freezes. Ice expands. The concrete cracks a little more each winter. Dry concrete doesn't have this problem. Keeping moisture out of your foundation extends its life.
Water Entry Predicts Problems
If water is getting in somewhere, the path for that water could be getting worse. A crack that seeps today might be a crack that flows next year. Monitoring where water gets in helps you address problems before they grow.
My Moisture Monitoring Tools
Didn't cost much. Provides ongoing value.
Pin-Type Moisture Meter
I bought one for about $30 at a hardware store. Has two pins you press into wood or poke at concrete. Reads out moisture content. I use it on my sill plates and floor joists quarterly. Looking for elevated readings that would indicate moisture getting in.
So far, everything reads dry. Under 10% for the wood, which is normal. If I ever saw readings above 15%, I'd investigate.
Hygrometer
A $15 digital hygrometer sits on my basement shelf. Tells me humidity. My basement runs about 50-55% most of the year, occasionally up to 60% in spring. That's acceptable. Over 60% consistently would mean too much moisture getting in.
Water Alarms
I have three of these, about $10 each. One by the sump pump, one at the northeast corner where I used to get water, one at the lowest point of the floor. They shriek if they detect water. Haven't gone off once since I fixed the drainage. But they're my early warning system.
My Eyes
Most important tool. Looking for stains, efflorescence, wet spots, damp patches. I walk the perimeter twice a year, sometimes more often after heavy rain. Visual inspection catches most moisture issues before they become serious.
Where I Check for Moisture
Problem areas get extra attention.
The Floor-Wall Joint
This is the most common water entry point in basements. The joint where the wall meets the floor can admit water under pressure. I check the entire perimeter for staining or dampness along this joint. My northeast corner still has old water stains from before I fixed the grading. But no new moisture in years.
Around Cracks
Cracks can admit water even when dry. I check moisture around my tracked cracks, especially after rain. Elevated readings near cracks would mean they're not watertight. So far, mine are dry. I sealed one crack specifically because it was showing slight moisture after rain.
Near Windows
Basement windows and their wells collect water. I check around window frames for moisture, and I check the wells themselves for standing water. Clogged window well drains can force water into the basement through or around the window.
Sill Plates
The wood sill plate sitting on top of the foundation wall can wick moisture and rot. I probe mine with my moisture meter a few times a year. All reading dry. If they started reading wet, I'd have a moisture intrusion problem to track down.
When to Check
Timing affects what you find.
After Heavy Rain
This is when water problems reveal themselves. Within 24 hours of significant rain, I walk through the basement looking for any new moisture. Anything wet that wasn't wet before tells me where water is getting in.
Most of the time, everything is dry. But the one time I find a problem, I want to catch it immediately.
During Snowmelt
Spring thaw puts enormous amounts of water into the ground over extended periods. This is when basements are most likely to leak. I check frequently during snowmelt. It's when I found my original drainage problem.
Quarterly Baseline
Every three months, I do moisture readings on my sill plates and note humidity levels. These baseline readings help me understand normal conditions. If spring readings are always a little higher, that's normal. If fall readings suddenly spike, something changed.
After Drainage Work
Whenever I do anything that affects water flow, extending a downspout, adjusting grading, cleaning gutters, I check for effects on basement moisture at the next rain. The work should help, but I want to verify.
What the Numbers Mean
Understanding readings helps interpret data.
Wood Moisture Content
Under 15% is generally fine for wood in a basement. 15-20% is elevated and worth monitoring. Over 20% creates conditions for rot and mold. Over 25% is an active moisture problem needing immediate attention.
My sill plates run 8-10%. Bone dry. That's what I want to see.
Humidity Levels
Under 50% is ideal for a basement. 50-60% is acceptable but watch for mold. Over 60% consistently means too much moisture is getting in. Over 70% is problematic.
My basement averages about 52% most of the year. Runs a dehumidifier in summer when it creeps toward 60%. But the dehumidifier is treating humidity, not masking active water entry.
Establishing Baseline
Take readings when everything is dry. That's your normal. Future readings compare to this. If the same spot that reads 3% dry is reading 10% after rain, water is getting to it. The baseline makes the comparison meaningful.
Connecting Moisture to Cracks
The relationship goes both ways.
Water Causes Cracks
Saturated soil pressure can cause new cracks or widen existing ones. Freeze-thaw cycles in wet concrete cause deterioration. If moisture is high, crack activity might follow. Gary's wall crack coincided with his moisture problem.
Cracks Admit Water
Once a crack exists, it's a pathway for water. Monitoring moisture around cracks tells you whether they're letting water through. A crack that's dry after rain is well-sealed or in a dry area. A crack that shows moisture needs attention.
Tracking Together
I keep my moisture observations in the same notebook as my crack measurements. Looking for correlations. Do cracks seem worse when moisture is higher? Does water entry increase after crack width increases? Understanding the relationship helps with prevention.
The $89 Lesson
My cheapest fix taught me the most.
The Original Problem
Water in the northeast corner after rain. Freaked me out. Thought I had foundation problems. Called around getting repair quotes. Someone was going to sell me interior drainage for thousands of dollars.
What Rick Noticed
Rick came over, looked at my basement for thirty seconds, then walked outside. Pointed at the downspout. It was dumping water directly at the foundation. The grading sloped slightly toward the house. All the rain from half my roof was ending up against that corner.
The Fix
Downspout extensions to direct water 6 feet away from the house. Some dirt to fix the grading so water flows away instead of toward. $89 in materials and an afternoon of work. Problem solved. Permanently.
The Ongoing Lesson
Now I obsess about where water goes around my house. Every downspout is extended. Every grade slopes away. Every time it rains hard, I mentally trace the water flow. Moisture monitoring starts outside the house, with drainage. Fix that first, and many interior moisture problems disappear.