I watched a roofer named Miguel go down in Fort Worth last July. 102 degrees on the ground. God knows what it was on those black shingles.
He’d been drinking water all morning. Thought he was doing everything right.
He wasn’t. Here’s what nobody tells you about hydration in extreme heat.
The math of sweat
Miguel was sweating about two liters per hour. That’s what happens when you’re working on a surface that hits 160 degrees.
He was drinking about one liter per hour. Seemed like a lot. It wasn’t enough.
By 11 AM, he’d lost four pounds of body weight in sweat. That’s the danger zone. Lose more than 2% of your body weight and your performance tanks. Lose more than 4% and you’re in heat exhaustion territory.
For a 180-pound roofer, that’s a 7-pound sweat loss. Miguel was almost there.
How much water you actually need
The old rule was “drink before you’re thirsty.” That’s wrong. Thirst is actually a pretty good indicator—most of the time.
But in extreme heat, you need to get ahead of it.
For roofers in 90+ degree weather:
- 16-20 ounces (about half a liter) before you start
- 8 ounces every 15-20 minutes while working
- Don’t go more than 30 minutes without drinking
That adds up to about a liter per hour in moderate heat. In extreme heat—100+ on the ground, 140+ on the roof—you might need one and a half liters per hour.
Here’s the thing: Your stomach can only absorb about a liter per hour. If you’re sweating faster than that, you’re fighting a losing battle. You need breaks, shade, or a different approach.
The electrolyte problem
Remember: Miguel was drinking water. Plain water.
Here’s what went wrong. When you sweat, you lose sodium and potassium. If you replace the fluid without replacing the electrolytes, you dilute what’s left in your blood.
It’s called hyponatremia. Your sodium levels drop too low. Symptoms look exactly like heat exhaustion: headache, confusion, nausea.
Miguel wasn’t heat exhausted. He was water poisoned. Same symptoms, different cause.
The right approach
Morning prep: 16 ounces of water with electrolytes before you climb the ladder. Not coffee. Not energy drinks. Water plus sodium.
During work: Alternate between plain water and electrolyte drinks. A 50/50 split is about right for most guys.
After work: More electrolytes. Your body is still recovering. This is when products like Built Daily Supply’s hydration formulas make sense—they’re designed to replace what physical labor burns through.
The pee test: Dark yellow? You’re behind. Clear? You’re overdoing it. Light yellow is the target.
The bottom line
Miguel spent a night in the hospital. Could’ve been worse.
If you’re roofing in summer, water alone isn’t enough. Your body is a machine. You wouldn’t run an engine without oil. Don’t run your body without electrolytes.