Author Topic: two story porch build (Read 944 times)

iosborne · « **on:** November 08, 2022, 06:05:25 PM »

So I'm in the early planning stages of a two story porch tear down and rebuild. You wouldn't want to see the existing porch cobbed together. Anyway my local sawmill gets mostly oak which I love to work with, but I am leery of it's reaction issues.
My dilemma is can I trust 20 plus foot lengths of green white oak to stay relatively straight/plumb for these porch posts? Order a few extra that I could always cut down for other projects?

Or do I build it floor by floor? I haven't seen a lot of that in timber frames for obvious reasons, the posts run to the plate, but can think of joinery that could work.
I've gotten 16' 8x8s from this Amish sawmill that I'm happy with, but even they are leery above 20 foot. They occasionally get pine, I asked him what kind and he goes 'oh i don't know the sticky kind'. Made me laugh. I wish I could still get hemlock oh well another gift from China.
I have looked into other sawmills but this guy is very reasonable and I haven't found anyone else so helpful. Kind of thinking out loud here so I guess I am wondering mostly about the option of floor by floor building and joinery. Anyways thank you!

Don P · « **Reply #1 on:** November 09, 2022, 07:34:22 AM »

That's a fully loaded series of questions

.
Can you trust a 20' stick of white oak? No, you can't trust a 2' stick. I would expect multiple culls prior to and dissapointment after. It's a heavy oak timber in the weather. If you are on board with everything having that timber in the weather entails, then proceed. It will not remain furniture quality. It will likely twist, check and decay more heavily and rapidly than pressure treated timber.

Actually box, or platform framing is not uncommon. The real "rule" there is that column members should begin and end at a point of lateral support. Studs supporting the work above can run from floor to floor but you don't want to put a hinge in the middle of the wall at midheight... and by extension, it isn't a real great idea to build high posted capes and such either

Tom King · « **Reply #2 on:** November 11, 2022, 08:40:17 AM »

I built a timber framed two story porch out of treated Pine in 1983. It's still is in fine shape, and has seen several hurricanes. Posts are 12x12x16' and span both stories. Those columns sit on short brick piers. I set the pieces with a crane.

iosborne · « **Reply #3 on:** December 19, 2022, 06:29:44 PM »

iosborne · « **Reply #4 on:** December 19, 2022, 06:41:43 PM »

Thanks for the replies. I am curious what folks think of this design. Is there too much going on at the 8x10 intersection?
I did come across this http://www.buildingarchaeology.org/wp-content/uploads/2015/03/Jettying-Floor-Framing-Hewett.pdf which was very interesting to read.
I realize my design varies from the bressummer quite a bit. Tried to keep it simple but it's possible I need to redesign without the 2 ft cantilever. They want the second story screened in otherwise I would bring the outer posts back over the lower posts. Any input is greatly appreciated.

iosborne · « **Reply #5 on:** December 20, 2022, 09:45:07 PM »

iosborne · « **Reply #6 on:** December 20, 2022, 10:00:31 PM »

ok theres a rough sketchup without all the joinery detailed. Was planning on soffit tenons for the joists, stub tenons for second story posts and anchoring those back posts into the stone house. But the more I look seems like a lot of bearing out in no mans land on weakened 8x10s. could incorporate a beefy jetty brace but even then.. Have I over sailed the jetty and time to abandon ship?

Don P · « **Reply #7 on:** December 20, 2022, 10:29:17 PM »

For me, oh yeah

Everything from the floor framing down would be treated, hangers, boring and safe. I'd look at why the joists are running in that direction, not that it is incorrect but it might solve some issues. But, that is the world I live in

.

iosborne · « **Reply #8 on:** March 13, 2023, 12:01:00 PM »

Thanks for you replies. Don you are right to change joist direction. It turns out that because the 2nd story is an increase in area that would require a variance and that is not worth the extra trouble anyway.
I am curious what folks recommend for 2 story post attachment to the frame. Seems I could use a splice plate down to a lower member, a steel post base (which always seems flimsy to me especially in compressive strength), or a stub tenon. Wondering if anyone has any other creative ideas? I can't find the requirement in the code.
Also curious what experience folks have with inspectors and splices/scarfs. Seems per code all splices have to be over posts yet many have scarfs over braces. Is this something that can only be surmounted with a stamp?

Don P · « **Reply #9 on:** March 13, 2023, 02:01:36 PM »

Technically the residential code, the "prescriptive" IRC building code applies only to light frame construction. If you follow the prescribed methods, span tables and charts, you may build without the oversight of a RDP, registered design professional.. an engineer in this instance, an architect is optional. Heavy timber falls under the IBC which requires a stamp. Enforcement is local, my understanding is PA has gotten tighter. Which, to me, that design deserves an engineer.

I'm not sure which post base connection we're talking about? Any holes down into the frame outdoors even with drainage are admitting water into the timber.

iosborne · « **Reply #10 on:** March 13, 2023, 02:18:00 PM »

I was referring to a simpson post base with standoff or something similar. Everything gets holes in it which then get filled in. They could be sealed or flashed which may be self defeating as it would trap moisture too, but there will be a roof overhead. With a tight waxed joint how much water can get in there? It could get toe nailed or screwed to lower member to have no cavity. Just wondering how others would approach a 2nd story platform or box frame. There could be a timberlinx connection but that too would be a cavity.

Forestry Forum
Sponsored by: