Bill Danna

06:42AM | 02/26/03
Member Since: 02/25/03
3 lifetime posts
I am looking for the proper way to do floor framing over an existing concrete porch. The porch has a full roof over it, and I'm trying to determine the best method for framing on top of the existing concrete and expanding the living space.

Can anyone provide some guidance for me on the best approach to framing this out.

I've looked for resources on the internet, but have found very little information on this topic.



07:00AM | 02/26/03
Member Since: 12/27/02
543 lifetime posts
How close is the top of concrete slab to your interior finish floor?

Then we can walk you through it, fairly simple, it'll be pt sleepers or joists dependent on that height.

Bill Danna

12:04PM | 02/26/03
Member Since: 02/25/03
3 lifetime posts
It's about 6 inches at the close point to the house, increasing to about 7 inches at the furtherest point from the house.

Couple things that concern me most are how to protect against moisture, and do I need to cut the concrete slab where it would go beyond the new outside wall?

Thanks for your help.


06:34AM | 02/28/03
Member Since: 12/27/02
543 lifetime posts
You'll be using treated 2x6 on edge @ 16 o/c w/ 3/4 T&G ply.
Find the exact height at the door, taper the joists to obtain level, on the oposite end you'll use a 2x8 ledger ripped to level & use joist hangers to get the 7" fin floor.
Layout the joist and connect the ledger to the house at the 6" side, lay down a 6mil poly on the existing concrete.
The 6" side will get ripped blocking between the joists rather than hangers, ask if you don't know what that is.
You'll also need to have solid blocking at 7' min across the span, so most likely a row midway.
Insulate with the polyisosianurates sheets, or styrofoam sm it also acts like a moisture barrier & you'll get more r factor per inch, you want to get r-13 so a 3" sm will get you R-15.
You'll need to cut the slab at the perimeter as you suspected, there you'll need to hang the sheathing at least an inch past the concrete for moisture.

Bill Danna

08:47AM | 02/28/03
Member Since: 02/25/03
3 lifetime posts
Thank you

A couple of questions:

1. The ripped blocking, could you explain further, you were right, I'm not familiar with this.

2. For the styrofoam sm, do I just cut this from a sheet and place between each set of joists, right on top of the plastic?

3. What's the maximum span I can have for the 2x6 joists?


07:51PM | 02/28/03
Member Since: 12/27/02
543 lifetime posts
1. The ledger & joists will be cut to match the height, so you will need to cut the blocking to match (rip: cutting in the direction of the grain).
The blocks are used in lue of metal hangers due to the height restriction. They are nailed between the joists to the ledger. Then the joists are nailed to the blocking. It's how we did it before metal hangers.
2. Yes, the poly will go under the joist for a coninuous barrier, the sm can be cut and fit in for the R factor. You'll get an air flow for the bays because the one end of the joist will be up on hangers, so if you place two vents at these wall locations it will help with any moisture build up as well.
3. I don't know the species for your area so I'll assume DF (doug fir) #2 at a live load of 40 and dead load of 10 @ 16" o/c it would be 9'9. In your case that span will be from where the joist contacts with the concrete to the larger ledger with the hangers.

Note: You should always contact a local building dept. if you are in doubt of any project, they are there to help.

[This message has been edited by Altereagle (edited March 01, 2003).]

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