A rooftop deck is the ultimate space-saving hack for a tiny house. It doubles your outdoor living area without increasing your footprint. But to get up there, you need a hole in your roof that doesn’t leak.
Installing a Roof Hatch (or egress skylight) is a high-stakes project. If a window leaks, you ruin some drywall. If a roof hatch leaks, you ruin your ceiling, insulation, and potentially your subfloor.
This guide covers how to select, frame, and flash a roof hatch specifically for a Tiny House on Wheels (THOW).
The Height Restriction Challenge
Before you cut a hole in your roof, you must check your clearance.
- Legal Road Height: 13′ 6″ (in most US states).
- The Problem: Most commercial roof hatches sit on a “curb” that sticks up 6–12 inches.
- The Math: If your roof peak is at 13′ 4″, adding a standard hatch will put you over the legal height limit.
- The Solution: You need a Low-Profile Hatch or an Egress Skylight (like Velux) that sits flush or nearly flush with the roofline.
Choosing Your Hatch
1. The Commercial Curb Hatch
- Pros: Heavy-duty steel/aluminum; built-in gas struts; bomb-proof latching.
- Cons: Industrial ugly; poor insulation (R-value); adds significant height.
- Best For: Flat-roof tiny houses where the roof is well below 13′ 6″.
2. The Egress Skylight (Recommended)
- Pros: Looks like a window; lets light in; sits low to the roof; high residential insulation value.
- Cons: Expensive; requires careful handling of the glass.
- Best For: Gabled roofs and lofts where every inch of headroom counts.
Installation Steps
Step 1: Framing the Rough Opening (H3)
You are cutting through your structural rafters. Structural integrity is key.
- Double Headers: When you cut a rafter, you must install “headers” perpendicular to the cut ends to transfer the load to the adjacent uncut rafters.
- Double Trimmers: The rafters on either side of the hatch usually need to be doubled up (sistered) to carry the extra weight of the hatch and the person climbing through it.
- Squareness: The box must be perfectly square. If it’s a parallelogram, the hatch won’t seal, and it will leak.
Step 2: Building the Curb (If needed) (H3)
If using a curb-style hatch:
- Build a 2×6 or 2×8 box on top of the roof deck.
- Insulate the Curb: This is often forgotten. If you don’t insulate the curb box, it will condense in winter and drip water onto your head, mimicking a leak.
Step 3: The Flashing (The “Make or Break”) (H3)
Waterproofing depends on your roofing material.
- For Metal Roofs (Standing Seam/Corrugated):
- You cannot just caulk a hatch on top of metal ribs.
- The Correct Way: You must install the hatch before the roofing panels. Use a “curb flashing kit” that wraps up the sides of the hatch. The metal panels then terminate at the bottom of the curb, and a counter-flashing hangs down over the top of the panels.
- For EPDM/TPO (Flat Roofs):
- The rubber membrane should run up the side of the curb and over the top edge under the hatch flange. This creates a seamless bathtub effect.
Step 4: Security and Gas Struts (H3)
- Wind Uplift: A roof hatch is a sail. If you forget to latch it and drive down the highway, the wind will rip it off. Install a padlock or heavy-duty internal draw latch.
- Gas Struts: Opening a heavy door while balancing on a ladder is dangerous. Ensure your hatch has gas pistons (like a car trunk) to assist with lifting and to hold it open while you climb out.
Maintenance Tip: The Annual Seal Check
Roof hatches vibrate during travel.
- Inspect the Gasket: The rubber seal around the lid can dry out or get compressed. Wipe it down with silicone spray twice a year.
- Check the Flange Screws: Road vibration can back out the screws holding the hatch to the curb. Check them annually and re-seal the heads with lap sealant.
Conclusion
A roof hatch transforms a roof from a “lid” into a “living room.” By choosing a low-profile model to stay road-legal and doubling down on your flashing efforts, you can enjoy sunsets from the top of your tiny house without worrying about rain getting in.