hello everyone,
our ground level wood deck is covered by a lexan roofed sloping structure which I built. It sits on 4 4X6 posts set 3 ft in the ground in concrete. Across the posts are 2X12 header type beams glued and screwed with angle supports on each side. 17 ft span. Rafters are 2X6 on 24 in centers--their span is 12 ft. Across those are the 1X4 crossing boards to attach the lexan.

It is sloped toward the house and overlaps the house roof to avoid putting a gutter on and to allow for open sky looking out and away from the house.

i want to change this cover into a second elevated deck. to do this i'll need to raise the side abutting the house roof. I will do this by cutting each of the two 4X6 posts and using two jacks. After it is up and nearly level to allow for drainage I'll insert new sections of post and secure them using double steel plates on each post with 8 bolts. i'll have the plates made.

max anticipated weight will be 1000 pounds in addition to the decking material which will be 2X6 treated lumber.

I would like to place the decking directly on top of the lexan which is the 20 year version with 10 years left on it. This would allow the upper deck to continue to serve as a cover for the lower deck.

I need to figure out a way to fill in the valleys in the lexan along each rafter so as not to crush or break the lexan.

Also I'm writing to ask if this plan is flawed and in how many ways. I'll post a picture later today.

thanks in advance for your interest and comments.

I don't know what the codes are in your area but here. The maximum span for a 2x12 floor joist on 16" centers is 12' (feet).

quote:

Originally posted by ron45:
I don't know what the codes are in your area but here. The maximum span for a 2x12 floor joist on 16" centers is 12' (feet).

Hum. I live in the county here, but I expect code is likely the same as city and as most other places. Doubtful it's more restrictive.

the structure i've built may not already be in code. i didn't think i needed a permit for a deck roof. but a change to a deck probably would require a permit.

i was hoping the current structure could work as a deck with limited loading. the 2X12 primary beams are doubled up with 5/8 plywood in between, glued and screwed. and the angle supports reduce the span to less than 12 feet. but i've only got 2x6 rafters on 24 in. centers. i wonder if doubling up would be enough support? Dang, this could get expensive what with treated wood costs nowadays.

This message has been edited. Last edited by: Ricker62,

To make your life a little easier, ron45's numbers are either just off or are more restrictive in his area compared to 'normal'. I'm looking at the latest copy of of framing specs for decks - got it from my inspector about two weeks ago. This is all based on IRC numbers:

2x12 joists set 16" OC can span 18'-10"
2x10 joists set 16" OC can span 16'-1"
2x8 joists set 16" OC can span 12'-10"

Just so you know.

I'm not getting a clear picture of what you are doing but the weak point I see are only having four support points for the entire deck. If this is one post in each of four corners then you will likely have some sagging over time. However, it this means there are four posts in a line and the other half of the deck is supported by a ledger on the house, then it could be fine. Again, I'm not getting a clear picture of what you have to begin with.

First....
Let me say that I am sorry for typing in the wrong information. What I meant to say is.

2x12 floor joist on 24" centers is 12' (feet).
I should say different wood will get you different max. lengths. I will also say if you use the IRC max. lengths you will have a bouncy deck.

hey, no worries. you are trying to help and that's much appreciated of everyone. i'll take some photos tomorrow evening and post them. at the same time i'll take some more precise measurements of spans, etc.

i tried to post pics. smallest i can make them is 200kb. dang, that's small, but this site only allows 100!!!!