diff --git a/health-check.sh b/health-check.sh
index 32bf594..8aba9a1 100755
--- a/health-check.sh
+++ b/health-check.sh
@@ -62,6 +62,17 @@ check_disk() {
             ok "Disk usage at ${pct}% on $mount"
         fi
     done < <(df -h | awk 'NR>1' | grep -v ' /dev' | grep -v ' /sys' | grep -v ' /proc' | grep -v ' /run' | grep -v ' /snap' | grep -v 'overlay2' | grep -v 'docker')
+    local used_kb total_kb total_pct
+    used_kb=$(df --block-size=1K / | awk 'NR==2 {print $3}')
+    total_kb=$(df --block-size=1K / | awk 'NR==2 {print $2}')
+    total_pct=$(( used_kb * 100 / total_kb ))
+    if [ "$total_pct" -ge 90 ]; then
+        fail "Total disk usage at ${total_pct}% on / — critically low"
+    elif [ "$total_pct" -ge 80 ]; then
+        warn "Total disk usage at ${total_pct}% on /"
+    else
+        ok "Total disk usage at ${total_pct}% on /"
+    fi
 }
 
 check_common() {