It's January, the house has no HVAC yet, temps are hovering around 40°F and the finisher is running a propane torpedo heater in a closed-up house.

Immediate Problems:

1. Propane heater safety hazard - Carbon monoxide buildup in a sealed house is life-threatening. This must be stopped immediately.

1. Temperature too low for drying - All-purpose joint compound requires minimum 50°F (per manufacturer specs) to properly cure. At 40°F, the compound will stay soft and never fully dry.

1. Moisture trapping - Cold surfaces + warm humid air from the heater = condensation throughout the structure, ruining taped joints and creating mold risk.

What Will Happen:

• Tape will bubble, peel, and fail within days
• Compound will remain tacky, never harden properly
• Moisture damage to walls and ceilings
• Potential CO poisoning

Immediate Fixes:

1. Stop using the propane heater - Use electric heat or ensure proper ventilation
2. Raise temperature to 60-70°F minimum
3. Use a dehumidifier to control moisture
4. Switch to setting-type compound (90-minute) which cures chemically rather than by drying
5. Extend timeline - allow 7-10 days minimum for proper curing

Code Reference: International Residential Code requires 50°F minimum for interior finishes. OSHA 1926.55(c)(1) mandates CO monitoring when fuel-burning equipment is used in enclosed spaces.

This job will fail completely if continued as planned. Stop work until proper heat and ventilation are established.

You will get joint failure, bonding issues, and a serious safety hazard.

The Chemistry (USG/GA-216): All-purpose compound requires 55°F minimum (air, substrate, and material) for 24+ hours per coat to cure via hydration. At 40°F ambient:

1. Evaporation stops. Water cannot leave the mud.
2. Hydration stops. The chemical set doesn't happen.
3. Result: You are stacking wet slurry on wet slurry. The tape embeds in soup. When heat eventually arrives, differential shrinkage cracks every joint; tape bubbles/looses adhesion; mud powdery/soft.

The "Morning Recoat" Fallacy: Recoating over uncured mud traps moisture. The propane heater adds massive humidity (1 gal water/100k BTU). You are creating a mold incubator behind the tape.

The Code/Safety Violation (IMC 303.3, IFGC 303.3, NFPA 54):

• Unvented heaters are prohibited in tightly sealed residential structures during construction (oxygen depletion/CO risk).
• Makeup air is required. A "closed-up house" has none.
• Fire hazard: Propane + drywall dust/flammable vapors (paint/primer later) = explosion risk.

*The Fix (Do this now):*

1. Stop taping. Pull the heater out.
2. Install temporary heat: Indirect-fired (vented) construction heater ducted in, or electric. Maintain 55°F+ constant (not just daytime).
3. Ventilate: Open windows for air exchange (drywall needs dry air to cure).
4. Switch material: Use setting-type compound (Durabond/Easy Sand 45/90) for taping/first fill. It sets chemically, not just by drying. Still needs 50°F+.
5. Timeline: Minimum 5–7 days proper cure before paint in these conditions.

Tell the finisher: "No heat, no tape. We wait for the permanent HVAC or a proper indirect heater. I'm not warrantying mud that freezes or ferments."