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Author Topic: "cheating" post and beam construction  (Read 30764 times)

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Offline Night Raider

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"cheating" post and beam construction
« on: May 23, 2009, 09:14:48 AM »
I've tried searching for this but not too much luck.  I'm looking at building a new post and beam sugar shack and a mill shed, not sure in what order yet.  I have no experience with post and beam construction but I have done lots of stick framing. 
They're both going to be very simple structures with just a single sloped roof, probably 9' high on the high side and down to about 6.5' on the low side and a width of about 10' and basically the sides would be open for now.  All the posts I am going to use rough 5.5X5.5 and probably the same for the beams across the top of the posts.  But on the mill shed I'll have a bigger beam over the 19' openeing, I just have to figure out how to cut a beam longer then the longest log my mill can cut, but that's another problem. 
Then for the rafters I was just thinking 2X6s seemed like the easiest (but if there was simpler way to do it with beams I'd be open to suggestions).
I was thinking of a concrete peir in a sonotube under each post with a metal bracket bolted to it to hold the 6X6.  The joints between the post and beams are what I was really wondering about, I was wondering if there are metal brakets available to make that joint instead of cutting a mortise and tenon?

Any advice at all on this project would be appreciated.

Thanks

Offline Jim_Rogers

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Re: "cheating" post and beam construction
« Reply #1 on: May 23, 2009, 01:45:14 PM »
First of all, welcome to this section of the forum.

Your design should be carefully understood and possibly reviewed to insure that the sizes of these timbers you want to use are large enough for the load they will be carrying.
From your profile I see that you're in Ontario. You'll need to know the snow load for your area to correctly size the beams for holding up the rafters. As well as correctly size the rafters.
Especially the mill shed roof.

Once that is done then you can size the joinery or brackets to hold the timbers in place.

Whatever you do, have fun doing it!
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Offline Night Raider

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Re: "cheating" post and beam construction
« Reply #2 on: May 23, 2009, 02:01:58 PM »
Thanks Jim,
I've looked at the building code for sizing up the beams and rafters, a 2X6 on 24" centres is enough and I've sized up the beam for over the big opening and I'll either need double posts or make bigger posts but it will still be 6" wide, the beam will be 6x10 hemlock I believe.  I've looked at home depot and they don't seem to have an obvious bracket for what I'm trying to do, I assume I'm looking for a formed piece similar in construction to a joist hanger.  The only other thing I was thinking was a flat metal nailing plate on either side.

Offline Rooster

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Re: "cheating" post and beam construction
« Reply #3 on: May 23, 2009, 03:50:27 PM »
Hey Night Raider,
There is a fastener system called Timberlinx that is used to help connect timbers, and posts to concrete. If you did an internet search you will probably find it.

Also, I don't own a mill but I know a few guys that do.  We have used a sliding deck system to mill logs longer than the mill can handle normally.  We have used LVLs (Laminated Veneer Lumber) (1 3/4"X 11") or larger. You can buy it in very  long lengths 30ft+.  Depending on the diameter of your log, you might use 1 or 2 LVLs side by side.  The LVLs are laid across the log supports on the mill like as if you were decking it.  The log is then placed on top of the LVL, and wedged so that it won't roll and the narrow end is shimmed and raised to max out your cut.  Taking a pass with the mill, ending close to the end of your mill rail stops, shutting down the blade, and then pushing the LVLs, log and saw carriage backwards, sliding across the deck supports, and then starting up the blade again and finishing the cut.  For instance, if your mill cuts 16ft, but you want to cut a log that is 20ft,.....cut into the log about 5ft, stop, push it all back so the carriage is back to the start point , then finish the remaining 15ft. 

Good luck!
Rooster
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Offline WILDSAWMILL

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Re: "cheating" post and beam construction
« Reply #4 on: May 23, 2009, 05:33:01 PM »
socket manufacting makes some. arkanasawer has used them he has a reference some were here or on wood web
i have been planning to but not yet
Kascosaw2B

Offline Night Raider

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Re: "cheating" post and beam construction
« Reply #5 on: May 25, 2009, 11:44:33 AM »
Thanks for all the replies, the socket system brackets is kind of what I was looking for, they also seem really expensive for what they are, I may just buy some big angle iron and make something up myself.  Seeing some of the examples I'm wondering if my idea of construction is right, having 6X6 vertical posts then running 6X6 horizontal beams on top of them then just 2X6s on 24" centres between the two, then strapping I guess if I'm putting steel on or sheeted if I'm shingling.  This won't have a peaked roof , just like a stand alone lean-too. 

Any design advice/suggestions are appreciated

Offline Jeff

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Offline WILDSAWMILL

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Re: "cheating" post and beam construction
« Reply #7 on: May 25, 2009, 03:47:33 PM »
I plan on welding my own as I want bigger post than 6x6 got some square tubing end cuts from salvage yard at good price
Kascosaw2B

Offline shinnlinger

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Re: "cheating" post and beam construction
« Reply #8 on: May 25, 2009, 09:16:13 PM »
Hi,

You can make your own big boy "nail plates" yourself or have a machine shop take flat 1/4" steel and punch holes in it and then fasten the plate to both sides of your beams with through bolts.  I think Simpson also makes some, but they ain't cheap either.

Jim brings up an excellent point though on an engineer approved setup.  If it were me, I would look at Simpson and copy the relative layout, enlarging the plan to fit my specs, and use 1/4 " steel and 1/2" through bolts.  You could then show this to an engineer rather than having the engineer come up with the whole thing.  I skipped the engineer and the through bolts and lagged steel onto the joints in my barn and it has held up fine, but if I was to do it again, I would thru-bolt.
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Offline underdog

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Re: "cheating" post and beam construction
« Reply #9 on: May 25, 2009, 10:13:47 PM »
Do a search on pole barns.
That is about the cheapest/easiest construction method.

Offline ARKANSAWYER

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Re: "cheating" post and beam construction
« Reply #10 on: May 26, 2009, 01:25:35 PM »
 











  It is not cheating.  If they had steel square tubing they would have used it in times of old.  GrandPa would have killed for a box of timber tites and a cordless drill to run them with.

ARKANSAWYER

Offline jfl

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Re: "cheating" post and beam construction
« Reply #11 on: May 30, 2009, 01:51:47 PM »
Night Raider,

1) regarding cutting a beam longer than the normal sawmill span, there is a page in the knowledge base of the forum. Go to forum extras, knowledge base.  Here is a direct link:

https://forestryforum.com/tips/tips.cgi?display:1061208316-32360.txt

I neved tried it myself (and I would need a 25 feet beam, I'm not sure I have a tree that long that is big enough...)

2) I am also condirering building a shed over my mill.  However instead of  trying to use a 25 foot long beam, I'll build a truss using 6x6.  It might require more wood volume, and it will require more connector (pegged or metal) but milling nice 6x6x12.5 feet is much easier than a single 6x10x25 feet.

3) What is the snow load in your area?  To find the load on the beam you need:
a) figure out the ground snow load, the slope of the roof (minimal), the type of covering (slippery metal or non-slipery asphalt?) After that you must determine what portion of the roof snow load is distributed onto the beam. Then you can figure out what size of beam you need.   Here in Quebec, I have a snow load of 46 pound per square foot. With aspen, I can only reach something like a span of 9 feet with a 10x8, so I'd be a little bit surprised if you could reach 19 feet with a 6x10...



Offline Night Raider

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Re: "cheating" post and beam construction
« Reply #12 on: May 31, 2009, 10:37:39 AM »
JFL. Thanks For the link.  I'm not sure of the top of my head what the snow load is but the beam would only be supporting 5' (10' wide building) it may have been a 6X12 beam.  And that was for hemlock, before I cut the beam I'll probably revisit the numbers.

For those with experience is it a bad idea to use a "boot" on a concrete peir to attatch the vertical posts or is it much better to anchor them directly in the concrete, The posts are pine so I was hoping to keep them up a bit and use sonotubes to make peirs that are a few inches above ground.

Thanks for all the info.

Offline jfl

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Re: "cheating" post and beam construction
« Reply #13 on: May 31, 2009, 07:45:33 PM »
Night Raider,

Here is my quick calculation:

Eastern hemlock  no 2 Fb=575 psi.

Compensate for  load duration (snow load= 1.15) Fb* = 660 psi.

6X12 (finished surfaces) @ 660 psi can hold 2807 lbs.

if your load is on 5 feet by 19 feet = 95 sq feet.

So that beam can hold up to a snow load of 29 lb / sq feet.  That's not a lot for canadian winters (Where are you in Ontario?)

jf

Offline moonhill

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Re: "cheating" post and beam construction
« Reply #14 on: June 01, 2009, 07:55:47 AM »
How many of these beams are there?  2, one on each end?  If so, that is twice the 29.  I am not sure I am following the whole design, I need pictures.

Tim

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Offline ljmathias

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Re: "cheating" post and beam construction
« Reply #15 on: June 02, 2009, 06:11:32 AM »
Setting posts in concrete has some drawbacks- holds the moisture in contact with the wood to promote rot while having the post elevated on a metal boot allows it to dry and stay dry- may not be as "solid" in some ways but works fine.  Other alternative is to use pressure treated and set 4' in the ground- works better here than in concrete.  Remember that ALL wood rots, just some slower than others, so at some point in the dim, distant future you may (will) have to replace a post or two, and it's a whole lot easier if it's attached to a boot- hard to dig it out of concrete.

Best of luck...

Lj
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Offline ARKANSAWYER

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Re: "cheating" post and beam construction
« Reply #16 on: June 02, 2009, 08:03:02 PM »
 




I pour a pad and sonic tube of concrete to support the building.  This one is on a slope and we back filled it.  It is the support for Wanda's shed.


 




 Then I bolt a bracket like this and sit the post.  The post is cut to fit over the bolt in the center.


 





  This way if a post is damaged it can be replaced or spliced.  One buried in the ground it hard to work on.  Also Timber frames are a "point load" and just putting a post in the ground with out some extra support area in the bottom is asking for settling later.
ARKANSAWYER

Offline ljmathias

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Re: "cheating" post and beam construction
« Reply #17 on: June 05, 2009, 06:21:47 AM »
Right you are, Arky- just didn't finish all the details on the post in the ground- I usually infill with clean gravel or pour a footing for the pole to sit on to keep it from settling.  Course, that's if I'm not in a hurry which seems to be most of the time over the last few years.  Did my bigger pole barn with PT telephone poles set 4' in southern red clay and it's held up pretty good so far- about 6 years with so little settling I can't see it, but hey, I'm not looking all that hard either.

Lj
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Offline Night Raider

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Re: "cheating" post and beam construction
« Reply #18 on: June 05, 2009, 08:08:46 AM »
jfl,
I'm looking at a snow load of up to 38 lb/sqft so I need a beam to hold about 3800lbs.  I didn't entirely follow your calculations.  I'll have to try to dig up my calculations, I quickly put in my number in the forum beam calculator and it seemed to "pass" I think (I'm not sure I entirely understand it).  I'm having a hard time finding something I difinitivley trust.  The building code seems to only talk about laminated dimensional lumber.
Arkansawyer, That's what I was thinking of using for the posts, that one looks a lot heavier then I was thinking but no reason I should go light.

Thanks for all the help

Offline jfl

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Re: "cheating" post and beam construction
« Reply #19 on: June 06, 2009, 08:00:10 AM »
OK I did my calculation a little bit fast and working with assumption maybe wrong. Here is the corrected detailed version:

In Don's calc:
https://forestryforum.com/members/donp/beamclcNDS2.htm

I entered the following:
Load on Beam(pounds): 3800  (in fact 19 ft x 5 feet x 38 is more 3610, but let's stick with 3800 for now)

Span of Beam (inches): 228  (19 feet x 12 inch per foot)

Width of Beam: 5.5 (you mentionned rough 5.5 in your initial post and that's also the finished size of a 6x6 lumber)

Depth of Beam: 11.5 (it should be 11.25 if it would be surfaced commercial wood)

Here is the funny part: the woord design values.  What number are you using?  I'll make assumtion (which should reveal to be false) and you can correct me afterward:

Hypothesis 1: you take the number from Don's link from the calculator:
https://forestryforum.com/members/donp/Fblist.htm

The best numbers are:
Eastern Hemlock Beam and Stringer
Select Structural  fb=1350 PSI MOE=1.2 Million PSI Fv=155 PSI

One nice thing with canadian snow load is that it is only present in the winter... So we can compensate with a factor CD= 1.15 since the duration of the load is only 2 months (I wish...)

In fact, one should check if the all-year-long load (without the snow) is ok with the all year long strength and check if the winter load (with the snow) is ok with the winter strength.  However, the snow load is so dominant around here (for that beam at least) that we don't really need to check the rest.  You might also have to check for the wind load, especially if the mill will be exposed to wind, but I can't help you on that. Also if the wood is wet, its strengh has to be reduced. But let's assume that you'll put a good roof over that beam... Now let's go back to fb

F'b = 1350 x 1.15 = 1552.5 psi
F'v = 155 x 1.15 = 178.25
MOE isn't compesated for duration, so it stays a 1.2 million psi.

I enter this into Don's calculator and get:
PASS, FAIL, PASS for Fiberstress in Bending,  Deflection,  Horizontal shear .

Deflection is between 1/240 and 1/360, so since you are not going to use gyproc on that ceiling, It might work for you.

However you just used a top quality beam (no knots, no checks, no split, wood slope less than 1/15) . Well, in fact Select Structural Beam and Stringer isn't perfect wood, but it must be a nice piece of wood (at 6x12x19 feet).  You mentionned previously that you are going to use rough lumber and I'm under the impression you want to mill it yourself. I personnally wouldn't try to grade my lumber as Select Structural (unless it is really perfect) and I'll design my shed with #2, which is easier to mill/find.  Let's try that:

No.2  fb=750 PSI moe=0.9 Million PSI fv=155 PSI

so F'b = 750psi * 1.15 = 862.5
Moe stays 0.9 and f'v is the same for #2 grade:

Now I get fail, fail, pass. 

So now the beam should fail with the snow load. And it will deflect more (closer to 1/240)  If you reduce the load to 3610 lbs (like mentionned in the beginning of the post) it will pass the Fb test, but not the deflection.

So you should check if you care about deflection.  If not, can you produce a beam that will be that large and nice enough to meet the grades of B&S #2.  I still think a truss would use a few more connectors but it would be stronger and wood would be easier to find.





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