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"cheating" post and beam construction

Started by Night Raider, May 23, 2009, 09:14:48 AM

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Night Raider

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

Jim_Rogers

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!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Night Raider

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.

Rooster

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
"We talk about creating millions of "shovel ready" jobs, for a society that doesn't really encourage anybody to pick up a shovel." 
Mike Rowe

"Old barns are a reminder of when I was young,
       and new barns are a reminder that I am not so young."
                          Rooster

WILDSAWMILL

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

Night Raider

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

Jeff

Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

WILDSAWMILL

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

shinnlinger

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.
Shinnlinger
Woodshop teacher, pasture raised chicken farmer
34 horse kubota L-2850, Turner Band Mill, '84 F-600,
living in self-built/milled timberframe home

underdog

Do a search on pole barns.
That is about the cheapest/easiest construction method.

ARKANSAWYER

 











  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

jfl

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...



Night Raider

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.

jfl

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

moonhill

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

This is a test, please stand by...

ljmathias

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
LT40, Long tractor with FEL and backhoe, lots of TF tools, beautiful wife of 50 years plus 4 kids, 5 grandsons AND TWO GRANDDAUGHTERS all healthy plus too many ideas and plans and not enough time and energy

ARKANSAWYER

 




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

ljmathias

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
LT40, Long tractor with FEL and backhoe, lots of TF tools, beautiful wife of 50 years plus 4 kids, 5 grandsons AND TWO GRANDDAUGHTERS all healthy plus too many ideas and plans and not enough time and energy

Night Raider

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

jfl

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.




Night Raider

jfl,
Thanks a lot for explaining that.  What did you mean by truss?  The slope runs perpendicular to this opening, but building a truss is appealing too, I wasn't looking forward to trying to handle a 20' log that big.

Thanks

jfl

Night raider:

Here is a link to a thread on the a milling shed:
http://www.norwoodindustries.com/townhall/viewtopic.php?t=2190&highlight=sawmill+shed+truss

What I mean by truss is exactly what is shown on the last photo, copied here for your convenience:





I'm not saying that this design is exactly what you need, or that 2x4 or 2x6 will be good, that's the idea.  What I intended to do personnally (I'm looking for a 10x24 shed) is to use 6x6 and build a 6 foot high by 24 foot long truss:




On the top member, there is the bending load and the compression load.  Those have to be checked and might require a larger piece (6x8 maybe? I haven't looked at it)  All the other member work in compression or in tension. I'd use don's column calculator for the compression one.  Just to illustrate, let's calculate that for my shed:

The total load shown on the model is 50+100+100+100+50 = 400 (I was playing with shaped) Your load is 3800, so lets say that the number in that model have to by multiplied by 10 to fit the reality. So the largest compression force is 212x10=2120 lbs in compression. Since it is in diagonal, the member length is 6 x 1.4142 =8.5 foot or 102 inches. I punch those numbers into don's calculator at:

https://forestryforum.com/members/donp/columncalc.htm

I use the cheapest wood I have on my property (aspen: Northern Species #2, Fc = 350 MOE = 1.1 million) and I get a column capacity of 23931 lbs, so way above what is needed.

For tension, as far as I know, there is no stability factor to take into account, so you just multiply the surface by the strength, so 6x6x275 psi= 9900 lbs.  Still many times more than needed.

The difficulty will be the connectors. The connectors also have to support the compression or tension strenth. That is as far as I got into my reasonning, but I'll be checking the metal connector mentionned above in that thread: it looks like what I need.

jf

Brad_bb

Why post and beam?  I mean, as my timberframe teacher once said, "It will take the same time or less to cut real timberframe joints than it will to fab the metal brackets and fit them, so why not do the real thing?"  No metal means no rust or rot from the interaction of metal and wood and water. 
Anything someone can design, I can sure figure out how to fix!
If I say it\\\\\\\'s going to take so long, multiply that by at least 3!

jfl

Quote from: Brad_bb on June 09, 2009, 01:05:55 PM
Why post and beam?  I mean, as my timberframe teacher once said, "It will take the same time or less to cut real timberframe joints than it will to fab the metal brackets and fit them, so why not do the real thing?"  No metal means no rust or rot from the interaction of metal and wood and water. 

I'd be interested in «doing the real thing», mostly for cost (8x8R post cap to put a beam on top of a post from Simpson StrongTie is something like 140$!), but then I bought a few books, including "Timber Framer's Workshop" from Steve Chappell and researched in this forum and I found out that it joint have to be build tight, at least to 1/32th of a inch or 1/64th.  I have problem cutting wood up to 1/8th of a inch with a skill saw... (ok ok, maybe I can be as precise as 1/16 of a inch if I take my time and use a guide). But I don't see how I could be more precise than that with a wood chisel? Correct me if I'm wrong but if the joint isn't tight, it will not hold (be strong and reliable).

This brings me to how long it takes to make a joint: I've already read a thread on that subject a long time ago and I don't remember any conclusion: It depends on the joint. 

Which brings me to another question: Most of the time, traditionnal timber framing is done with wet timber, mostly because it would take forever to dry them and them (unless you use salvaged lumber).  Is it more difficult to chisel dried timber than freshly cut timber?

Don't get me wrong: I think Timber framing is an art and as such it's worth more than industrialy produced stuff.  But to hang on the wall, I'll take buy the cheap reproduction of the Mona Lisa (poster) instead of a an original painting from a living artist...

jf

witterbound

How long does it take to cut a joint?  It depends on many factors, principally, what kind of tools you have.  For example, I can cut a 2"x6" mortise with my mortise machine in about 5 minutes.  Then if I want the joint housed, it takes about 20 minutes for the housing, which I often rough out with a forstner bit.  I've found that I average about 45 minutes for most joints.   

Laying out the timber and joinery often takes as long as cutting it.  As with everything, you get better with practice (and more tools!).  I believe you will find that traditonal joinery has many rewards, but it takes time to do.  The metal connectors will save you a lot of time, if that's a constraint.  Just like most things, quality takes time.

Before you venture down the road of doing it the old way on a big project, start with something small.  You really need to attend a workshop or find a local timber framer to give you some learnin' before you tackle anything big.  You can't learn it all from a book.

Yes, it's more difficult to chisel dried timber than green.  Much more difficult in my experience. 

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