Raising Subfloor Height

Richmond

Hi, I'm preparing to finish some unfinished space in the second floor of my home. The unfinished space is about 14 x 14 with dormers in the front and back. It has a simple gable roof, so there is a flat ceiling, sloped ceiling, and knee walls. The unfinished space is about 5 inches lower than the floor height in the finished space. I want to bring up the floor height to match the finished space, but I'm not sure about the best way to accomplish this. Currently the room has 1/2 inch plywood over 10 inch joists spaced 16 o.c. I'm not really worried about the load, I'm simply trying to decide how to build up the floor, and how to fasten it. Is it reasonable to build a frame on top of the plywood? Should I run the new supports perpendicular to the floor joists? What is the best way to fasten this? Honestly, since I need to raise the floor up about 4 & 1/3 inches to accommodate 3/4 inch tongue and groove plywood, I just figured I would rip some 2x6's down to size and run these perpendicular to the existing joist but on top of the 1/2 plywood that sits on these currently. (after making sure the plywood was thoroughly screwed down to the existing joists.) I would then sit these 2x6's on their ends and glue them to the floor, and tie them into the walls with nails and maybe some sort of joist hangers? Possibly adding some cross supports. Any thoughts?



(P.S. I have some extra ceiling height, so I'm not worried about raising the floor)

just a guy

maybe screw 2x4 flat to existing floor deck and screw your new floor joist into the 2x4's side ways, cross bridging is a good idea

kwikfishron

A picture is worth .....

forresth

I'd say run ripped 2x6s diagonally, anchor them with long screws (maybe some landscaping screws), and block or cross brace it in a few spots.

Richmond

Thanks for the responses, just trying to get some different ideas.

UFoPilot

However you proceed, make sure you use LOTS of construction adhesive or you will have squeaks.

tfahlberg

How did it turn out? I have to do the same thing, and I was wondering what you ended up doing, and if you had any suggestions. Thanks!

Richmond

Actually, I ended up leaving the floor height as is because my wife decided she would prefer to have the additional headroom. Glued and screwed down another layer of plywood and installed prefinished hardwoods. Sorry I can't help you with the subfloor height issue.

tfahlberg

Thanks Richmond. No worries. I'll figure it out when I get there. I like the idea of a cross or diagonal layer of ripped 2x6s.