The safest way to strap a mattress to a car is by using ratchet straps or heavy-duty ropes passed through the open windows of the car's doors, creating a secure anchor point that locks the mattress down over the roof. This method prevents the mattress from shifting or flying off at highway speeds. You will need at least two straps, moving blankets or cardboard to protect the car's finish, and red flagging to mark an overhanging load.
The most critical step is creating a solid anchor. Do not just loop straps around the side mirrors or bumper, as they can break. Instead, open the front and rear doors on the same side of the car. Pass the strap through the door frame and close the door on the strap (be careful not to pinch the strap in the locking mechanism). Repeat on the other side so the straps crisscross over the mattress. Tighten the straps until the mattress is compressed and cannot be moved by hand.
| Item | Specification / Recommendation | Purpose |
|---|
| Ratchet Strap Working Load Limit | 1,000 lbs (454 kg) minimum | Ensure strength for securing load |
| Number of Straps | 2 to 4 | Provide multiple points of security |
| Mattress Overhang (Rear) | Max 3-4 feet (0.9-1.2 m) | Maintain vehicle balance and visibility |
| Red Flag Size | Minimum 12x12 inches (30x30 cm) | Legally required for overhanging loads |
| Speed Limit | Reduce speed, avoid highways if possible | Minimize wind force on the mattress |
Always use moving blankets or a large piece of cardboard between the mattress and the car's roof to prevent scratches. If the mattress overhangs the back of the car by more than a few feet, you are legally required to tie a bright red flag to the end. Drive cautiously, avoid sudden maneuvers, and check the tightness of the straps after the first few miles. For large mattresses like king-size, a roof rack is a much safer investment, but the door-anchor method is the best option without one.
