New porch floor – to subfloor or not to
The porch floor is on the to-do list for my 80-year old home. I just ripped up 3 of the 5/4″ end boards and lo and behold! No subfloor! I now have a lovely temporary skylight into my basement, plus a question. With these old floor joists 18″ on center, should I do which of the following to minimize bounce in the finished porch floor?
1. Lay new tongue and groove 5/4″ mahogany right over the existing joists, with a dose of construction adhesive on each joist? 2. Lay a plywood subfloor first, and undercut the bottom clapboards and the door threshold to allow enough room for even the thinner grade of mahogany? 3. Lay a plywood subfloor first, and remove the bottom clapboards and the door threshold and rip them to fit (easier achieved with the clapboards than the threshold)? 4. Skip the subfloor, double up on the floor joists, which span about 10′, and would be easily accessible once the old floor is up? Photo available at http://www.phaze-3.com/porch.jpg
Replies
First ya gotta ask yourself....how bad was the "bounce" in the original floor?
5/4" T&G is gonna stiffen those joists up pretty good.
If it was that bad, I'd go with the beefing up of the framing as opposed to adding a subfloor.
Can you add a girder at midspan?
J. D. Reynolds
Home Improvements
Bounce was slight. Then again, we're on a busy street and typically use the back door, not this door. No place to hang a girder midspan, but plenty of room for a few extra joists between the 18" centers. My gut feeling was to avoid a subfloor.
NEVER use subfloor on a porch. Those deck boards will get wetted and they need to dry both ways.
IP` can span 24"OC, I'm sure 5/4 Mohagany can handle 18"
What puzzles me is the view into your basement. The deck is not a roof. To cover something like this roofing a living space, the whole design and procedure is 100% wrong.
Seal all six sides of the new T&G before installing it. One thing I have done that helps is to use Gorilla glue in the grooves. It expands so it will fill the space left that typicallly traps moisture that accelerates rot.
Another option you could consider is to use Tendura on this deck.
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Looked at Tendura, but it's thinner than the original flooring, which is 5/4, which would mean more trim work than I care for at the moment. Will go with the 5/4 mahog, sealed, glued and screwed, on the original joists.
As for the top finish, I'd rather stain and seal than paint. The porch is covered, but open, and gets it's share of rain snow, southern exposure sun, and a healthy dose of road grime. I've read positive and some VERY negative things about Cabot's Flame Mahogany - something about Cabot changing their formula. Or, should I think like a boat builder and go with spar varnish?