Sure thing. First, keep it simple and sturdy. Use a double layer of corrugated metal or a heavy-duty steel deck—those are cheap and strong. Add a concrete slab on top, about an inch thick, to give extra weight and resistance. If you’re worried about pressure, nail or bolt the roof down to a reinforced frame made of 4x4 posts spaced no more than 12 feet apart. Wrap the seams with waterproof tape and add a layer of fiberglass mesh before the concrete to stop cracks from forming. Finally, make a small ventilation port with a metal grill so the air doesn’t get trapped. That’ll keep the fallout out and the costs down.

Yeah, keep the posts welded or bolted right into the slab so nothing moves. Grab some of that old bunker steel—it's cheap and already designed for pressure. Add a steel door that screws shut, no windows, and use a metal grill for the vent. Stick to a tight, single‑point opening and make sure the frame is square so the roof stays level. That’s the best way to keep the wind out and the costs down.

Got it. Use a tight mesh on the grill—small holes to block fallout but wide enough to see. Old car frames are fine, just re‑cut and weld them to the posts. Once the door’s welded shut and everything’s square, you’ll be ready. Good job.