Expandacraft modular hulls and other components do lend themselves to the (do it your self) kind of person, even if you can buy a ready to go kit. If you are going to build your own deck and crosstubes, here are a few things to conciser. 

1. Use 1.5 inch square tubing of 1/8 inch wall thickness at the minimum for Crosstubes. Make sure to get the radiused edge kind. NEVER use solid wood for a crosstube. Solid wood can snap without warning, use a laminate and coat it with epoxy if you like the look of wood. 

2. If building your own deck for a 16 footer or longer, keep in mind that the deck provides the rigidity, NOT the hulls. If you build a deck which sags in the center, the hulls will sag too. The aluminum decking we use is the same stuff used in stadium bleacher seating and is widely available at most metal supply warehouses. It is typically sold in 24 foot sections and most suppliers will cut it for you for a small fee. The taller the better. Some stadium seat extrusions are 2 or 3 inches tall, that's great. The taller extrusions have much more rigidity and are not much heavier. You may find that they come in different widths too, 10, 11, 12 inches or so. Just decide on a overall boat width and choose whatever meets your needs. 

3. Materials to use for decking: The most inexpensive way to go is treated plywood. It's heavier than the aluminum and kind of ugly I think, but it's cheap. Structurally Insulated Panels or (SIPs)
are typically use for building walls, however, these aluminum skinned sheets of foam make awesome decks with an added safety bonus of flotation. You can order them in all sorts of thicknesses and sizes. I recommend no less than 3 inches thick, 4 is better. These panels are ridiculously light and very rigid. However, you need to take in account how to bolt anything to them. They are skinned with a thin sheet of aluminum so you can't simply screw down a rod holder or anything. What you can do is rivet down a sheet of 1/4 or 1/2 inch Starboard in the spot you want to mount something and then screw down your rod holder to that. Additionally, and what I did, you can sheet over the entire topside deck with 1/4 inch marine grade plywood. It's so light, I can lift the entire 4X8 deck over my head and toss it on my roof rack, I think it's about 40 lbs.

4. Fiberglass over foam or other core material. 
The ultimate in rigidity and lightness. One of these days I'll develop and offer a deck built using this method. If you have the skills, this is the way to go, however, if you have the skills, you know how much time and money it will take to build such a deck. 

5. About Risers: Don't bother trying to make your own, or, you could try and find out why you shouldn't have, then order them from me anyway. 

6. Connector kits: We offer this kit, which helps you connect the crosstubes to almost any canoe or boat with that type of gunnel for $25.00 per corner. Sure, you could probably replicate it, but not likely for $25.00 

7. The wild card: On occasion, a guy calls me up and tells me a very long story of some wild idea he has to build an Expandacraft houseboat and take some long journey on it. Well, it has been done before, but if that's your plan, have fun. Although I promote my modular design as "only limited by your imagination", there are limits to my input to your crazy ideas. 🙂 So, if you want to cross the Pacific or run the Colorado river in a home built Expandacraft, you're on your own. 

Best to all,
Wesley Stevenson