Several manufacturers had aluminum floors in the 1980's but their popularity has waxed and waned for the past thirty years. It was claimed that they were discontinued because of cost, but in the modern era when pontoon boats seem to be built with no concern whatsoever for cost the aluminum floor has never made a come back. I suspect that it has more to do with manufacturing labor than costs. Assembling aluminum planks 20+ feet long and locking them together takes more labor than fastening pieces of plywood.
There has been discussion that aluminum decks sometimes feel “spongy” or springy to walk on, however I suspect that people who like aluminum decks would think they're just fine.
An aluminum deck may not be the benefit to the rebuilder. You never have to change the plywood but getting glue off an old aluminum deck to put down new carpet can be a huge project. Sometimes the old carpet pulls up but often the carpet backing sticks to the aluminum and it can be a nightmare removing the old glue and scraps of carpet.
New boat manufacturers and rebuilders have experimented with composite material for decks. A product is officered by Coosa Composites LLC, Alabama. But like aluminum floors, the idea has never widely caught on. Composite flooring is generally more expensive than wood and in some cases it's considerably heavier (almost twice the weight of plywood).
In 2018 the Forest River brands (Berkshire, South Bay, and Trifecta) adopted a one-piece composite deck. The deck is one large piece (18’-27’) of 8’6” wide composite. It's claimed to be lighter than plywood. Marine grade plywood decking is about 63 lbs. a sheet. We’ll have to wait and see if it will replace wood decking.
A Final Thought on Wood-Aluminum and Composite flooring.
As explained elsewhere the entire marine industry is geared towards the new boat buyer. Decking treated against rot with an extended warranty (sometimes 50 years) was introduced in the late 1980’s. Because of the improvement in wood decks, interest in alternative flooring seems to have declined. If a CCA wood deck will last 20 years, even though its warrantied for 50, that’s probably enough to satisfy most new boat buyers. They realize that the carpet, furniture and top will show age over time. Plus, the children and grand children that the boat was bought for might not be visiting as often. The rebuilder faces a similar situation. How long do you really need your rebuild to last. If your boat has a good used-engine, there is reason to believe that you may get another 8+ years out of it. A floor that will last forever might not be worth extra money. It’s like so much that I’ve dealt with in this website, when is good, good enough and better just more?
Deck Joint Tape
The joint between decking should be sealed. This prevents water from working its way up between where the pieces of decking meet. Butyl tape laid on top of the cross channel (where seams meet) will prevent wet lines in your carpet. Another method is to simply to caulk the deck seams.