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WillK 11-06-2011 11:38 AM

Pre-planning: converting front room back to porch
I'm in the midst of a lot of work and I'm approaching floor joist and subfloor replacement. The front room on our house seems like it was originally a porch which was converted to a part of the interior space.

So here's some relevant details of the project: The house is on concrete blocks and was built in 1917. There is a triple 2x6 beam in the center and 2x6 floor joists butt over that beam. These are on 16" spacing. Under the front room there are 2x4 joists on 24" spacing.

I am installing new support structure specified by an engineer, although I am making modifications due to interferences - I've run the modifications by the engineer and the city inspector, and they have no issues since I am increasing from the original specifications. For example, originally the triple 2x6 beam was remaining, and 2 triple 2x10 beams were going in at the outside. I am getting rid of the center 2x6 and using 4 triple 2x10 beams, replacing the 2x6 joists with 2x8 joists which will be lapped over the 2nd and 3rd beam.

So for the porch, I'd like to know if there's requirements related to the height of the porch floor relative to the floor of the house. If it's an open porch, does the porch floor have to be lower to prevent water intrusion? Is there a height requirement that relates to tripping hazards?

At this point my primary concern is planning for the floor joists, and if the floor of the porch is the same as the interior floor it's 2x8 joists on the beams, if it's lower then maybe I have to notch 2x8 joists, or if it's too complicated maybe I stick with the porch being enclosed.

ddawg16 11-06-2011 11:56 AM

If an open porch, you want it lower....I don't think there is any standard.....I'm putting in a balcony on the second story of my addition....and the floor level on it is 2" lower.

Sounds like you have a lot of 2x beams.....have you considered going with a PSL beam? I think you could get more strength with less.....surprised the engineer didn't spec it.

Another option...instead of being on top of the main beams, you could use joist hangers....I would suggest that over notching joists. Not to mention the fact that I don't think you can notch the joists any usable amount.

WillK 11-06-2011 12:42 PM

My understanding, which I don't know that it's necessarily correct, is that 1/3 is allowed, and I was considering building my beams up to the existing 2x6 and later replacing with 2x8 but notching with precision over an entire house would be difficult... Might be that it requires a ledger board or joist hangars... I also was consider going to 2x6 joists for the porch. Being that the porch doesn't have the load of a second floor above it, and also being that I'm reducing the span, I'm sure 2x6 should be okay.

I'd check span tables before I went through with it, but regardles I mostly am interested in understanding any floor level placement requirements there may be for the time being.

I'll consider the joist hangar option, I think an 8" would probably be plenty for water intrusion and make the step fairly obvious. What I would need to understand, though is how do I handle the part that is outside the beams? Of course, I don't think I'd be entirely opposed to losing that last 6" either.

And another question comes up, is there any way that an open porch could be built where the triple beam underneath doesn't need to be PT? One beam is already started using non-PT douglas fir.

WillK 11-06-2011 12:47 PM


Originally Posted by ddawg16 (Post 765046)
Sounds like you have a lot of 2x beams.....have you considered going with a PSL beam? I think you could get more strength with less.....surprised the engineer didn't spec it.

I basicly am constrained on that matter to what I can work with myself and what I can snake through the crawlspace and all the pipes, wires, pillars of concrete blocks and furnace that is in there. There would be no way I could easily get a 1-piece beam into the crawlspace and into position.

Demolition of the house would've been the easy way to get everything done, but we're buying on land contract and living in the house so we can't drop the property value on any kind of interim basis without the sellers approving, and I can't get into anything that would leave a huge hole to outside up for more than an hour or so at a time. So I'm stuck doing this the hard way.

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