Author Topic: 12 x 16 House  (Read 123419 times)

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Offline Beavers

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Porch design help needed
« Reply #25 on: July 04, 2009, 09:56:44 AM »
Thanks for the detailed drawing John.  [cool]

Poppy,

I'm looking forward to following along with your timber frame construction!  Have you built timber frame before, or is this the first?
One of these days I want to buy some land in northern Minnesota and build a timber frame cabin there.  Here in Nebraska there's not much timber, so to buy big beams cost big $$$  d*


I'm building a 8' deep covered porch on the front side of the house, and have a few design questions.

I'm planning on using continuous 4x6 posts from the footings to the porch roof.  I would then bolt a 2x8 onto each side of the posts for the floor joists to rest on.  From what I've read this is not allowed by code, they want you to notch the posts or have the beam sit on top of the posts.  Doing it that way, I would them have to use some kind of brackets to then attach a second post to go up to the roof?  Doesn't seem as strong to me.  ???  What am I missing here?

I was also thinking that it would be better not to have the shed roof over the porch tie directly into the house roof.  My thinking is that in high winds the porch roof has a lot higher chance of getting blown off, and if I have it tied into the house roof it will also take that roof with it.  Is it ok to attach the high end of the shed roof to a ledger board bolted to the side of the house?

Thanks for any help on this.




Offline poppy

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Re: 12 x 16 House
« Reply #26 on: July 04, 2009, 10:28:48 AM »
Quote
I'm looking forward to following along with your timber frame construction!  Have you built timber frame before, or is this the first?
OK Beavers, now you've gone and done it.  You've asked the critical question, am I a virgin builder?  Yes, I am. :-[ There I said, I feel better now.

I did take a wood shop class in high school and built a bookcase out of ash, and turned a few goblets from bowling pins.  I also built a few wood items when I was in 4-H, and built a couple of things for the band in HS.  I did some minor home improvements at my parents house.

During the college years I built my own sterio (Heathkit) and speaker boxes; then I built a complete sterio system for my sister-in-law.  And I built a toy box for my daughter (was a baby myself when we got married).

Since I worked for a residential steel door company for awhile, I was able to salvage some doors (entry and french) and installed them in our second house.

So yea, this is my first real construction project. As I said in my build thread, I know just enough to think I might just be able to do this. There are a variety of reasons for going slow and one of them is to learn as much as I can before the next phase, which, if you've been following my progress, doesn't always work. d*

Sorry about the long answer to a simple question.


Offline John Raabe

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Re: 12 x 16 House
« Reply #27 on: July 04, 2009, 11:06:59 AM »
Consider this as an option for the porch beam that doesn't rely on the shear of the bolts.



(This sketch based on the  wrap around deck and porch plans (Sht. 6) for the 20' wide 1-1/2 story cottage.)
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Offline PEG688

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Re: Porch design help needed
« Reply #28 on: July 04, 2009, 11:07:41 AM »




I'm building a 8' deep covered porch on the front side of the house, and have a few design questions.

I'm planning on using continuous 4x6 posts from the footings to the porch roof.  I would then bolt a 2x8 onto each side of the posts for the floor joists to rest on.  From what I've read this is not allowed by code, they want you to notch the posts or have the beam sit on top of the posts. 


  Humm, I don't think your idea would be a issue, I'd thru bolts the 2x8's , your just looking at deck load here so that would be workable down at the deck level.  If it's a code build the building dept will let you know if this meets code in your area. If they have a issue with the two 2x8, thru bolt a beam on the inside of the posts. I really think the double 2x8 would be excepted.

   Doing it that way, I would them have to use some kind of brackets to then attach a second post to go up to the roof?

  Your continuous post would be the better way.  

   Doesn't seem as strong to me.  ???  What am I missing here?

  It the top a beam might be a better idea if your in a snow load area. For a couple of reasons

  #1:  a beam will take more weight.

  #2:  You'll have a easier time getting solid bearing from rafter to beam with one surface , the beam top , to attach to.

 Use H-1's to tie both your floor joist and your rafters to the beams.

 
 



 


I was also thinking that it would be better not to have the shed roof over the porch tie directly into the house roof.  My thinking is that in high winds the porch roof has a lot higher chance of getting blown off, and if I have it tied into the house roof it will also take that roof with it. 


  Is it ok to attach the high end of the shed roof to a ledger board bolted to the side of the house?

   Sure lag bolt a 2x10 to each stud , two per stud , all the way across , two lags into each stud , per drill to prevent splitting the studs.

   Lay out your rafters so the miss the studs , or let in flush every lag bolt head and use this hanger to attach your rafters to the ledger,

 

   



b]

Thanks for any help on this.






 G/L PEG
When in doubt , build it stout with something you know about .

Offline PEG688

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Re: 12 x 16 House
« Reply #29 on: July 04, 2009, 11:12:17 AM »


Consider this as an option for the porch beam that doesn't rely on the shear of the bolts.





 How much shear have we got on a exterior deck? Whats the shear strength of two 5/8" or 1/2 " galv. thru bolts?

 I think his method would work , whether it's code pass-able I don't know.

 The knotch you drew would work as well ,    IF   ,   he used 6x6 instead of the 4x6's he mentioned.

 

 
When in doubt , build it stout with something you know about .

Offline PEG688

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Re: 12 x 16 House
« Reply #30 on: July 04, 2009, 11:18:10 AM »


You might take a look at this thread. http://countryplans.com/smf/index.php?topic=1418.0



 Nice to see this threads been useful.  [cool]
When in doubt , build it stout with something you know about .

Offline John Raabe

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Re: 12 x 16 House
« Reply #31 on: July 04, 2009, 11:32:26 AM »
PEG: I agree that the shear force is unlikely to exceed the strength of the bolts (I show 2 - 5/8" lags) and the post needs to be a 6x6. (You may find that the square 6x6 also looks better.) Local code may require a bearing notch but either method is likely to be fine structurally, especially for a near grade deck. Things get more serious for a high deck or 2nd level - both at the beams and at the ledger.

PS - PEG's visual tutorial on notching is very helpful (see link above).
« Last Edit: July 04, 2009, 12:00:06 PM by John Raabe »
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Offline PEG688

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Re: 12 x 16 House
« Reply #32 on: July 04, 2009, 12:05:48 PM »

 Ya  a 6x6 would be a better post choice in this case.
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Offline glenn kangiser

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Re: 12 x 16 House
« Reply #33 on: July 04, 2009, 12:16:56 PM »
Just a note from some things I have banging around in the cobwebs upstairs.

The shear on the bolts is much greater than the fiber stress of the wood will support.  As I recall the 1/2 or 5/8 lags support around 500 lbs or a bit more each allowable due to fiber stress on the wood.  Shear on the bolts is likely in the area of 8 to 10,000 lbs each.

Fiber stress on an inch and a half notch in a stud should allow around 1500 lbs.  These are just rule of thumb numbers I keep in my head -- likely stretching capacities a bit as I round them up and wood types vary.  

Please feel free to correct me if these numbers are way off or you know the correct ones. :)
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Offline Don_P

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Re: 12 x 16 House
« Reply #34 on: July 04, 2009, 04:11:01 PM »
The 2x8's bolted on the posts is prohibited, I imagine you're remembering the detail with the circle and slash through it showing that from DCA6. That document is being picked up nationally, and its just bad practice, you're asking to split the beams. You could stand a 2x6 under them to the footing as long as they were well nailed to the 4x6. That would be the strongest option IMO. You can also mount hangers on the sides of the posts, the kind with the ears turned in and run the beams from post to post. That gets done in post frame sometimes, don't care for that one though.

(Glenn, Whitlock, thats a thought too, weld em up with the angle turned in next time, bolts and ears hidden, less obvious  ;))

A 1/2 bolt through a 4x with a 2x on each side, in SYP, loaded perp to side member grain, wet service, is good for 559 lbs/bolt. 5/8 bolts are good for 788 lbs per bolt. If we call the deck load 50 psf and if you had a pair of 1/2" bolts then 1118/50= 22.36 square feet could bear on that connection. Add some weathering...
here's the link to the connection calc set up for the 1/2" bolt described;
http://awc.org/calculators/connections/ccstyle.asp?design_method=ASD&connection_type=Lateral+loading&fastener_types=Bolt&loading_scenario=Double+Shear&mm_type=Southern+Pine&mm_thickness=3.5&mm_thickness_text=&theta_angle_mm=0&sm_type=Southern+Pine&sm_thickness=1.5&sm_thickness_text=&theta_angle_sm=90&fast_dia=0.5&load_duration=1.0&wet_svc_factor=0.7&temperature=1.0&submit2_LBD=Calculate+Connection+Capacity

Lets calc bearing on a notch or the end of a 2x6. We're worried about crushing the side grain of the 2x8 on the notch here;
#2 SYP compression perp to grain is 565 psi, wet service = 565 x .67=378.55 psi allowed
1.5" X 5.5" X 378.55=3123 lbs
Divide that by 50 psf=62.46 square feet allowed on that one notch, double that if you bear both rims. So if you either notch them in or stand 2x6's up under each 2x8 you bolted through the allowable load goes from 1118 lbs to 6246 lbs. Add weathering induced checks, no strength problems.

Well, Glenn asked  :)

If you have some blocking mounted between studs above the upper floor and bolted the ledger to them rather than weakening the studs I'd be happier but that's getting into my opinion not code.

Never cheap out or underbuild a deck or porch, they cause deaths about monthly, failures weekly. We were shown slide after slide of failed decks and railings that caused massive injuries and deaths, almost always family and friends, usually at a party, wedding or funeral.

One thing that would work here at the house side is to simply mount joist hangers to the lower treated beam. Then there is no ledger hanging on something the beam is supported from posts under it. A step and landing at the door, and a shorter flight of steps to grade. Just a thought.

Glenn, one more, you got me curious. minimum yield on bolt steel is 45,000 psi. 1/2" bolt... pi *R^2 *45000=8831 lbs bending yield strength. I couldn't find a top link pin last week while moving some rocks, used a bolt, it looks like a pretzel  :D. But you're right, although it yielded, the steel doesn't fail till way up there, the wood is without a doubt the weak link.

Oh notch in a stud, dry use .. SPF is only 425 psi 1.5x1.5x425=956 lbs. DF/SYP would get up to around 1200 lbs in dry use, wet wood crushes at 2/3 what dry wood does.

Offline glenn kangiser

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Re: 12 x 16 House
« Reply #35 on: July 04, 2009, 10:04:33 PM »
Thanks for taking the time to do the numbers, Don, and it looks like I may not kill myself with my rule of thumb numbers at that. 

I'm really a steel guy and a bit of a lazy one at that but in general know enough about strengths to make myself dangerous.

I found that in working on Caterpillars, if I welded the grade 8 bolts onto the machine to hold guards they would break off easier than a soft bolt which yielded and bent rather than fail.  How that applies to this discussion I don't know - but thought I would throw it out there anyway. :)
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Offline Don_P

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Re: 12 x 16 House
« Reply #36 on: July 05, 2009, 03:06:39 AM »
One way it relates. People oftentimes want to frame with screws. Most screws are hardened to some extent so that the heads don't strip out while you're driving them. Instead of a ductile failure, which is what you want, bending and slowly failing, they just snap, a brittle failure, no warning, not good. My helper figured that one out when he screwed some toeboards up on the roof, Whee!

Offline Beavers

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Re: 12 x 16 House
« Reply #37 on: July 05, 2009, 07:49:03 AM »
Thanks Guys!

I had to read thru it all a couple times to process all the info.  :o

I'll go with the 6x6 posts, I wanted to avoid them just because they are such a PITA to cut, but it looks like they are what I need.
For the roof I do the same thing as the floor?  Notch the posts and bolt in the doubled up 2x8's?


I found a ton of info on the web for regular deck design, but couldn't find anything for one with a roof over it.  d*

Offline Don_P

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Re: 12 x 16 House
« Reply #38 on: July 05, 2009, 08:57:28 AM »
One old design you might find on some of the land grant university ag plans is the post notched on each side to accept the roof carry beam and 2x material ripped the same width as the remaining width of the notched post, 2-1/2". This is nailed between the beams alongside each rafter and protrude above the beam to nail to each rafter or truss. There's your hurricane tie. It would work below for the deck too if you go that route. Spacing those members can be a bee and bird concern though.

Offline Don_P

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Re: 12 x 16 House
« Reply #39 on: July 05, 2009, 03:46:29 PM »
Backtrack warning;
You had asked a couple of days ago what I meant when I mentioned a horizontal beam to help reinforce the tall gable wall. We've asked a few homeowners if we could build them a plant shelf on the gable wall ;) This helps to stiffen a tall wall. see if this pic makes sense;

Offline Beavers

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Re: 12 x 16 House
« Reply #40 on: July 05, 2009, 04:46:12 PM »
Backtrack warning;
You had asked a couple of days ago what I meant when I mentioned a horizontal beam to help reinforce the tall gable wall. We've asked a few homeowners if we could build them a plant shelf on the gable wall ;) This helps to stiffen a tall wall. see if this pic makes sense;



Thanks Don, makes perfect sense now... a picture really is worth a thousand words!  [cool]

I like the old school hurricain ties too.  I've got more time than money, so ripping some 2x4's sounds a lot better than giving more of my cash to Simpson!  ;D


Offline csiebert

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Re: 12 x 16 House
« Reply #41 on: July 10, 2009, 05:29:31 AM »
I cant tell from the picture, but you might want to use Pressure Treated Plywood for your plumbing box.  I did a similar thing with 1/2" CBX and it went about 14 inches below grade and the plywood de-laminated and edges were rotted in about 5 months.  Replaced it with 5/8" PT plywood and after a year, its holding up just fine.

Offline Beavers

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Re: 12 x 16 House
« Reply #42 on: July 10, 2009, 06:04:45 PM »
I used PT 2x4's and PT 3/4 plywood, so hopefully it should last a few years.  ;D

Offline Redoverfarm

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Re: 12 x 16 House
« Reply #43 on: July 10, 2009, 06:22:23 PM »
You could also use "concrete backer board" .  I think it would last about as long as anything else.  Besides it would be impervious to insects.  You could also sparay foam the interior for some frost or freeze protection.

Offline John Raabe

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Re: 12 x 16 House
« Reply #44 on: July 10, 2009, 06:27:45 PM »
Don_P

Great plant-shelf wall stiffener! A tall gable wall may face the view and be made mostly of windows - This is especially true of vacation homes from the 1970's. In a storm those window walls can flex and drum in a pretty frightening way.

Your horizontal beam could stabilize that wall and serve as an indirect lighting trough, bookshelf or any number of uses. Cuts way down on the flexing too! :D
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Offline Don_P

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Re: 12 x 16 House
« Reply #45 on: July 11, 2009, 07:53:14 AM »
We are a decade or two behind the times  :D. This is another wall stiffening scheme. I stood up steel plate in a pair of columns that flanked the center stack of windows in a tall window wall.

This was a log wall below with a big hole in the wall and stick framing above. I got some 10x10 timbers and put one on top of the log wall between the windows and door to act as my "plate" then stick framed above it. I've also bolted large beams inside of a regular stick framed wall like the plant shelf drawn above. Just a few more ways to stiffen things.


The plumbing chases here can become termite highways, its a good place to dump some boric acid or similar, lime would probably even do it.

Offline poppy

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Re: 12 x 16 House
« Reply #46 on: July 11, 2009, 08:10:58 AM »
I have been a little concerned about how to efficiently stiffen my high gable walls, since the loft does not extend to either end.

Thanks for the ideas, Don.

Offline John Raabe

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Re: 12 x 16 House
« Reply #47 on: July 11, 2009, 10:15:26 AM »
Since I am in earthquake country some of my custom home designs have incorporated welded steel moment frames (these stiffen and absorb shear in walls with lots of openings). I'm sure Glenn has made many of these.

They certainly work well but are for the most part custom designed, and custom fabricated. My engineer at the time was just out of employment at Boeing and loved these things. I'm sure the home owner spent an extra $10-12k and the builder would have rather worked with wood, but nobody worries when the wind blows in off the ocean.
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Offline glenn kangiser

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Re: 12 x 16 House
« Reply #48 on: July 11, 2009, 01:49:50 PM »
I have done tons of moment frames that were designed by engineers.  One  4.5 million $ cabin - with moment frames hidden inside of 2 to 3' diameter logs. d*




There were many in the above cabin.

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Offline John Raabe

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Re: 12 x 16 House
« Reply #49 on: July 11, 2009, 06:00:51 PM »
And it all looks so casual and rustic! :D :D ;)
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