I actually tried one of those fire pit pads last year, mostly because I didn't want to spend a ton redoing the deck if things went wrong. Here's how it went for me...
First off, they're pretty easy to set up—just unroll and position under the pit. But here's something to watch out for: make sure your pad is large enough. I underestimated the size at first and had some sparks land dangerously close to the edge (yikes). Once I sized up, though, it worked pretty well.
As far as moisture goes, I didn't notice any mold or discoloration underneath after several months. My deck is composite too, and airflow isn't amazing underneath, but the pad seemed breathable enough that water wasn't an issue.
My only gripe was aesthetics—it looked kind of bulky and industrial on my otherwise cozy deck setup. But hey, I'd rather sacrifice a bit of style than risk damaging the deck or worse...
I get what you're saying about the industrial look—those pads can definitely clash with certain aesthetics. When I set up my fire pit, I skipped the pad altogether and went with a layer of decorative gravel and stone pavers instead. It took a bit more effort, but honestly, it blended beautifully with the deck vibe and still protected everything underneath. Plus, sparks landing on stone felt way less stressful than watching them hit fabric...just something to consider if you're open to alternatives.
I went the gravel and stone route myself, and it's held up well. But just a heads-up from my experience—make sure your gravel layer is thick enough. I initially skimped on depth, thinking it wouldn't matter much, but after a few fires, I noticed some heat discoloration on the deck boards underneath. Nothing serious, thankfully, but it was a bit unsettling. Ended up redoing it with a deeper gravel bed and some thicker pavers, and it's been perfect since. Sparks hitting stone definitely feels safer than fabric pads, no doubt about that. Still, I'd recommend checking underneath every now and then, especially after longer fires, just to be safe.
Good call on the gravel depth—I had a similar issue when I built mine. Thought I'd done everything right, but after a couple of longer fires, I noticed the pavers underneath were getting pretty warm. Ended up adding an extra layer of sand beneath the gravel to help dissipate heat better, and it made a noticeable difference. Definitely agree about checking underneath occasionally...better safe than sorry, especially if you're using it regularly.
Good points raised here, especially about the sand layer. When I built my fire pit last summer, I initially thought gravel alone would be sufficient too. After a few uses, though, I noticed the pavers underneath were still warmer than I'd expected—not dangerously hot, but enough to make me reconsider my setup.
After doing some research, I found that adding a reflective heat barrier beneath the sand and gravel layers can also help significantly. It's basically a thin sheet of aluminum or specialized reflective material designed to bounce heat back upward rather than letting it seep downward. I installed one beneath mine, and it noticeably reduced the heat transfer to the base. Might be worth considering if you're regularly using your pit for longer fires or if you're concerned about heat buildup over time.
Also, another thing I've learned is that airflow matters more than you'd think. If your fire pit walls are too high or too enclosed, heat tends to concentrate downward instead of dissipating outward and upward. Adjusting the design slightly—like adding small gaps or vents around the base—can improve airflow and reduce heat buildup underneath.
Of course, regular checks are still essential. Even with these precautions, it's always good practice to periodically inspect the area beneath your pit after extended use. Better to catch any potential issues early rather than dealing with bigger problems down the road.
Just my two cents based on personal experience and a bit of trial and error...
