# Beam calculation



## dem45133 (Jan 8, 2012)

Good day gentlemen and any ladies.

I am in the middle of a major remodel and am jointing two rooms that are separated by a main support wall for the home. This place is a 105 year old "sorta cape-cod but without the dormers (yet)" 11 foot sidewalls to eave, 10.5" pitch. 4 rooms down 2 up centered over the bottom. 24×30 outside footprint. Upstairs "knee" walls are almost full ceiling height. The wall I am removing is holding up the second floor and by extension the roof… so its critical to beam correctly.

We are doing a special open joist ceiling of the bottom floor showing off our Douglas Fir floors upstairs and a brightening of our red oak full dimension joists. The open beam will set mid-span where the joists meet across a 24 ft wide gable. I do not want modern materials unless its hidden under matching rough sawn red oak… and I did research this some.

But… why not use the real thing? I have a woods full and so does my neighbor (who also has a 42" circular mill) where we can cut a solid red oak beam with the matching circular kerf marks just like our hundred year old joists are (as compared to band sawn). The ends of said beam will be inside a 4"wall sitting on 4×8 oak vertical posts set directly on the base plate on top of the center foundation. Being hidden I plan to through bolt 1/2" by 4" steel plate vertically between the support posts and the sides of the beam to lock the beam ends in place to control warping while it dries (yes it will be only air dried outside for some period of time before installing… but it will not be kiln dried. the load span will be 13'8" and I am leaning toward a 8inch wide x 12" (maybe 14") deep solid beam cut from one of our trees that has a clear 16ft section of trunk. While drying I may center and quarter post it temporarily… but not sure yet… it really should cure under a minimal load or none I believe.

Does any one know of an engineering calculator to calculate bearing capacity of a span… and the modulus of elasticity for red oak?. I grew up on a place with mortise and tendon east coast 250 year old barns that we put better than 50,000 bales in… still strong as it was when they built it… solid beams are certainly nothing new… but thought I'd ask for any opinions and a site for the calculator. Remember…this is all open construction and finished… no hiding places anywhere.

Oh, I am an scientist/engineer kind of guy… just not in civil… I can do the calculus on any of it but I am way way out of practice. Calculus classes were 35 years ago.

Calculator?

Opinions?

Many thanks in advance… Regards, Dave


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## nardir (Oct 4, 2011)

I"m looking into the bearing requirements for you, but I do know that the modulus of elasticity for red oak is 1063. kg/sq. mm, sorry don't have the standard version on hand only the metric. I'll get back to you soon on the the bearing issue. Any info you can give me on the projected loads would be useful.


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## dem45133 (Jan 8, 2012)

Thank you nardir.

Load is typical (plus) for this style home. The plus being books… the room above this wall is the library. About half of the shelves attached to the high knee walls… the others centered. So its a bit heavier then the standard bedroom. Raised seam metal roof and attic above that and over the eaves. The 6 ft wide eave storage on the outside of the knee walls are full of stuff too. So maybe its a double "plus". (good scientific terms here!) With all our books we've commented several times that it was a good thing this house was framed in oak. At least a 1500 lbs of books. Another 3000 lbs of stuff, at least, in the eaves. Two loads of books that squatted the H out of a heavy 3/4 ton. But about half are downstairs. 24×30 6 room cape cod style, 10.5 pitch roof. Two rooms upstairs centered over the 4 below. This support wall is basically centered down the middle axis as one would expect. The north 1/2 is being replaced by the beam creating a full width front room 23 by 13 ish inside measure. All and all, Id bet there is nothing shy of 8000 (if not 10k) lbs resting on the support wall including the structure. So figure that and double it for good measure. Not sure how it fits but I was also considering two 4 or 5 ft 45 degree braces in the two corners… mortised and tendon like a barn… that transfers some into the posts from the span.

Dave

Actually, just hold up a minute. I have to leave for work but I'll continue tonight. The is other design parameters possible too… with at least one mid post…. we'll talk to night. Dave


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## canadianchips (Mar 12, 2010)

Try looking at these sites:
http://[email protected] www.awc.org
http://ideasfordeckdesigns.com/calculators/beam-span-calcu
http://the-house-plans-guide.com/beam-span-tables.html 
I appreciate the look of a solid beam, although you will gain more strength from a laminated one !
Calculating the MAX load is a good idea, generally you use square footage x number of people at one time, the HORIZONTAL beam will require this square footage load, your VERTICAL post need to TRANSFER the weight to your footings. You can beef up your beam, your vertical posts all you want BUT if they are not sitting on a good footing everything will sag ! Every well built building starts at the BOTTOM.
Hope this helps.


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## JJohnston (May 22, 2009)

I'm a civil engineer, bridge engineer to be precise, and we have bridges in New Mexico with 20 to 30' spans with beams as big as you're talking about, and douglas fir at that. The numbers should still be run (and will be if you expect to get a permit), but off the cuff, you'll be fine.


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## dem45133 (Jan 8, 2012)

Thanks canadianchips and jJohnston. Just to reiterate as I said in the original post… the beam (and the current wall) sit on the mid span footer and concrete foundation wall. The two end posts will go through the floor and onto the base-plate of the 1st floor joists. House sits on one of the first poured concrete foundations in the county. The footers themselves are directly on bedrock. Not a single crack anywhere in 105 years. Other than heat/cold cracks in the lathe plaster walls… not a single settlement crack anywhere. House has never moved one iota. We live on top of a ridge and get quite a bit of wind too. I've been in "modern" homes that were shaking and creaking in strong winds to the point I was getting very concerned. We've had 80 mph winds here… and other that rattling of the old double hungs and whistling a little… house didn't even vibrate much… let alone shake, creak, and move about.

We are quite rural and are not required to get permits. We are totally un-zoned in anything other than ag or non-ag for tax purposes and we specifically sought that out when we were looking to buy 14 years ago. We are considered a farm and do have a meager farm income. The county is 95% owner occupied and we fight tooth and nail to keep it that way. Certain county powers try every now and then and we keep voting it down. Basically its our land… nobody else has any say in it… period. One would be hard pressed to ever convince me otherwise. The only thing we are restricted with is single-wides through deed restrictions which is very common now. The majority did it to themselves by not having any stewardship and tending to trash up their places… many do not,,, but enough did to have started the trend. I personally do not have any issue with them and have lived in two, my folks were one for 23 years, but we never trashed it.

Back to the subject.

The end posts will be on the foundation direct. Any mid-span will be too if we use them (but blocked under the floor in case they are only temporary while it cures for a couple years). Personally I do not want any posts… but with only a standard 8 ft ceiling… I also don't want it to to hang too low either. I really do not want to go more than a 12" deep beam. It can be 10 inches wide if you want but not more than 12 (preferably 11") deep. I considered an H beam and modifying the joists to set inside it (becoming almost a blind beam)... but that would be very very difficult to modify the joists and install and I'd then have to install full span tie rods as this is the old style roof system. not trussed. All my joists are tied to each other with two big 1/4 inch shank by about 6" spikes which are also bent over on the outer 1-1/2 inches. That's how its tied across now. It has to stay.

This isnt pine… its hard as nails 100 year old oak. If a nail from its construction never saw moisture you might get it out with a 3 ft wrecking bar… but more than likely you'll just pull the head off… that's once you chiseled your way under the head. It will heat up your blades and you have to pre-drill even the smallest screw… Sheetrock screws will twist off after about a 1/2' Even my Senco FramePro will not drive an 8d into it at a 125 psi (its limit). They built this place with green or wet oak… about the only way to do it. I'd love to find an old timer that remembers… but that is getting more and more unlikely as time goes by now. When I'm done with this project I have to build an addition to expand the kitchen… I'd love to match the construction if I can. I can always get logs sawn. So I keep researching.

Nardir… If your able, see what your numbers say for a 10" deep, 11 inch and a 12" at 8, 9 and 10 inches wide reverse respectively. An 8 or 9×11 or a 9 or 10 by 10 wont bother me… a 6 by 14 would be too deep.
A 14 would only have a 6'10 clearance. An 8 by 10 with two 45 degree braces at the two or three foot mark would be ideal and have a 7'2" clearance. But this is a a heavy static load house by its design, and we tend to have a higher than average dynamic load by default. Just the lathe plaster from 3/4s of the downstairs ceiling (on a small 24×30) home and the two sides of the support wall (studs still in place) weighed in at just over 4000 lbs. Since I'm not doing a ceiling now it won't have that weight, but all the rest of the house's lathe plaster is still intact and will remain so. I'd venture to say this construction is at least a a 1/2 again heavier than today's on static… if not more.

Well its bed time… Good night gentlemen.

Dave


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## canadianchips (Mar 12, 2010)

Sounds like you are on top of this project. No matter how much we think we know it is always smart to ask for other peoples opinions. Good luck with the rest of your remodeling. Post some pictures before and after if you can, I would like to see them.


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## nardir (Oct 4, 2011)

Dave

Sorry about the delay in getting back to you, been a bit busy around here, got a new saw and have a pregnant wife lol. From everything I can gather I would recommend going with a beam 10"wide x 12"deep and to also add those 45 braces, just as added strength for the possible extra dynamic loads, plus they add a nice flare to the room. I know it seems large but for that span and potential loads that would give you a nice secure beam with a little cushion of safety which is never a bad thing.


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## nardir (Oct 4, 2011)

Dave

I also looked into the 8×10 and it really shouldn't be done, you could get away with an 8×12 without the braces you are right at the span limit for that size, so with the added braces it would work, I am just a person who likes to always add a little extra beef to my projects, better safe than sorry I figure.


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## nardir (Oct 4, 2011)

So you know I figured these out myself, but also had a structural engineer at work look it over and he came up with the same.


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## dem45133 (Jan 8, 2012)

Thank you nardir.

Yes, I had reached the same conclusion… but going with a 9×11(dry) with braces. There is a duplicate thread on the HomeRefurbers forum (which is where I thought I was when I initially posted this, but went ahead and copied it over when I noticed it… ended up with two independent threads). There are several replies along the same lines and I found a neat reference you may like to see which specs a lot of the various non-typical woods (http://www.forestryforum.com/members/donp/Fblist.htm). It also had a nice calculator. Its located at http://www.forestryforum.com/members/donp/beamclcNDS2.htm if you'd like to see it.

This exercise has shown me that it is entirely doable so when the time is right my neighbor Steve and I will go to the woods and see what we can find that will yield a clear 16 footer. I will also go talk to some of my Amish neighbors (they are doing an old fashioned barn raising down the road).

Now its back to the open ceiling clean up, wall fill-ins in the old cavity areas, sorting through the stuff stored the eaves and installing the new Douglas Fir in them. Its coming along and it will be beautiful when its done…. but its a lot more work than I had initially planned on (Imagine That!!!!). I have set a deadline though for the entire project of April 30. We have to get on with our lives too (Not to mention the kitchen expansion.).

Later, and thanks…

Dave

PS… my wife says she takes issue with your sign-off…. in fact I issued her a Certificate of Achievement as a "Master Sander" when we we deep into several antique equipment restorations. She even displayed it on her cube wall at work for a while along with other pictures of our goats, goat kids, American Lineback cattle, and some of the equipment she worked on.


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## nardir (Oct 4, 2011)

Dave

Glad it all worked out. Good luck meeting your timeline, and tell your wife she must be leaps and bounds ahead of mine in terms of hands on skills.


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