dont know much about building boats so help

[texas steve]

i have a 27' pontoon boat and i striped it down to just the deck. i want to build a inclosed space on half of it and was wondering if i could make a wood frame out of 2x4's (like a house frame) for this and have it be strong enough to work.

[alan white]

Spruce is very strong actually. The method for marine construction would require:

Straight wood without cracks, loose or dark knots, sap, etc. Choose wood carefully. Go through the pile, sighting and examining every piece.

Screw together rather than nailing, and better still, glue with thickened epoxy top and bottom

Screw and glue (construction adhesive is fine) plywood to "studs". Or nail with ss ring nails, 7d. Set heads and putty (Bondo is okay for puttying and smoothing out, but epoxy and filler is better).

3/8" ply over 2x3s, 16" o.c., and 80" high is more fitting a boat to keep weight down.

Simply paint plywood exterior AND interior. Some filling will be involved, but keeping ecerything exposed will limit mold and rot. Do not hide framing behind non-removable panels or furnishings. you can dress up the studs inside by routing a bevel/chamfer on the corners facing inward.

Use PT lumber for bottom "plate". Also seal all playwood edges with epoxy after cutting but before installing. This can be done by buttering up the joints as you are attaching the ply.

The roof can be made from crowned spruce boards 12" on center to keep weight down, maybe 2" higher in the middle of an 8 ft span, using 1x5s and 1/4" plywood covered by rubber membrane roofing material. This is very light and will last as long as all is painted first, edges sealed with epoxy. It can be nailed on with stainless ring nails. The rubber is set in ribber cement.

Windows can be aluminum storms with screens, the kind used on houses, probably obtainable for free from window/siding companies. Aluminum storm doors are also okay, may have to be shortened.

Altogether, this should all help keep weight down. You can analyze the actual weight by calculating the wood at 35 lbs a cubic foot average, and then seeing what weight the pontoons are going to float. It is very easy to build too much weight into the structure, so think light whenever choosing materials. Leave plenty of reserve capacity!

Alan