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Author Topic: Does post and beam change the use of Green Oak timber, v true timber framing?  (Read 380 times)

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Offline MbfVA

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 I know there's been a great deal of discussion about using green timber versus dried, and most folks seem to come down that using green is OK in timber framing. Not that that's totally settled,  and I understand it's not a super simple question either.

 We are planning to use oak and other hardwood timber from our property as much as possible  for our new home.

My question is if we switch over to more of a post and beam type set up as  opposed to through joinery and timber framing, does that make a difference since we're not using the same system to join the wood, using more metal, etc?

 Thanks for the suggestions and thoughts as always.
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Offline Don P

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Green oak and raw steel do not play well together, they both are degraded. To some degree oak and steel wherever there is potential for moisture or condensation is a concern, so coat the steel in some way. Detail such that the wood is not subject to splitting as it shrinks... bolt low in beam seats, do not widely space bolts across grain, etc. Review the tech documents from the AITC website, think through the connections.

I left this discussion with a comment last time that still holds true. It is never better for the building to build with green materials. In the time you have been discussing this your timbers would now be 1 season drier. I don't say any of that in harsh tones it is simply a reality. I've watched folks on other forums wring their hands for as much as 5 years over this issue, and then build green... what in the world is going on in their heads  :D

I did take my meter to the job on Thursday and checked the 4/4 and 8/4 poplar we sawed in May-June and have stacked in the hay barn. The 4/4 was hitting 19-20% most often, the 8/4 was still quite variable but generally in the mid 20's.

Offline MbfVA

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 Got to get a designer first, Don.  Our building project is turning out to be one at least mildly from hell, and we haven't cut the first tree for the timber frame yet, haven't even got a design.

At this point, I am so fed up  with the inertia that seems to pervade that I consider our land still for sale. One designer told us point blank, go buy something out there already built, you'll save a bunch of money.  She's right, but land is hard to sell right now, especially with no house on it, with recently built houses being king.  At the height of the foreclosure dump off, stuff costing $2.5 million was going for 2/3 off. In the high end, bad things are still happening for sellers, or not happening depending on how you look at it.

It would come with a nice saw mill and lots of other equipment.  Rant mode off.

I recall that you disagree with using green, period, even on true TF.  I guess that'll never be settled 100% among the experts.  But what do you say to people who assert drying large timbers will twist & turn, etc, as they dry if not held in place in the structure, making re-milling/planing necessary before they can be used?

From what I've seen, most companies that provide framing timbers on any kind of mass basis or as complete packages to contractors work with soft woods, which have a whole different drying  profile.  Necessary corrections are easier to do in a factory setting, anyway, before sending anything out, and with what they charge, they can afford to do it.  Also, such producers are probably more sensitive to the appearance of the wood that they provide, since their clients who are not knowledgeable (my observation is that's applicable to lot of people having their own homes built, even those with money, around here) may get upset at later cosmetic changes such as splits etc.  No seller or contractor likes call backs.

We couldn't care less about that kind of thing.  I've seen bunches of cracks and twists in timber frame homes.  Rustic, we like rustic. We don't worry about no stinkin' cosmetics.

FWIW, a firm called Timbersmiths uses green timber for sure, including on a project in Albemarle (nr Charlottesville for those not of this area) costing several $million recently, that a guy who will be helping us worked on.  Everything they put up in the frame was cut and milled just days before delivery to the site.   Mostly oak from what CJ said.   That is confirmed by one of the owners there who has discussed our project with us.

Maybe depends on what part of the country you're in, or even within a state. Maybe it depends on the species, Oak in the case of that house, and it will be predominant in ours.

 I'm not trying to be argumentative.  It's a debate.  With my level of knowledge, I am relegated to observer & listener status for the most part.
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Offline Don P

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No the discussion is fine, my opinions come from disappointed customers over the years. Dad switched to glulam in the late 60's for that reason. I have found few who care as much as the customer after the check has cleared. I wish it were otherwise but recognize and be prepared for the reality. Separate hype from what you know of how wood behaves. Your oak behaves the same as my oak, the same natural laws exist where you live, I guarantee it. That is not to say that each tree is not an individual but you see my point. Look at work several years old not just recently completed work to see if that is acceptable. Pine certainly moves much less than oak, each species is also unique.

You really can't hold a timber in place if it wants to move, check or twist. If one does so ahead of time you can certainly cull it, remill it or cut it down. Would you rather heat with that twisted timber or make excuses and apologies, I've been there. I don't like looking back at a joint that was dollar bill tight and seeing it twisted and sloppy several years later. Is it still structural, sure, is it beautiful... that is subjective. If that level of fit and finish is acceptable then by all means build green, just don't build green and expect it to look like it was built dry, that isn't going to happen no matter what anyone says to the contrary. Will it be acceptable to you, only you can answer that.

 I imagine you can get a planing head for your mill. If you mill, dry and then dress using your mill it will also be jointing the timbers true. I got to do that earlier this year and it was a pleasure to work with those timbers. The barn project, we are felling, milling and the timberframers are using them right behind us. That is best for our schedules but is not to be mistaken for being best for the building.

None of this is meant in a harsh way, it is meant to help you think clearly and logically

Offline Don P

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This is the AITC publications list, the post and beam folks;
http://www.aitc-glulam.org/shopcart/index.asp
The timber design manual is expensive but you can probably get a look at it through interlibrary loan.

This is the section from the manual of typical details, pay particular attention to the connections to be avoided;
http://www.aitc-glulam.org/shopcart/Pdf/aitc_104_2003.pdf

From the manual and something I've told clients through the years. Run as cool as possible through the first winter.
Quote
Note; Heat should not be fully turned on as soon as the building is enclosed; otherwise, excessive checking may occur due to rapid lowering of the relative humidity in the building. A gradual seasoning period at moderate temperature should be provided.


A bit more in the USFPL's wood handbook, chapter 13;
https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_13.pdf

Offline PA_Walnut

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Great thread! DonP, I'm tuned-in and would like to purchase these guides you've listed. Do they delivery them in PDF form?

I'm in the earth-moving phase of my own timber frame outbuilding (not a house, but a rather ambitious workshop/man cave).

I'm faced with a related dilemma: I can purchase EXCELLENT white pine logs 2 hours away (big, straight, long and prime) for a reasonable price, which are on the ground now, sawed this week. Some are 24-30" diameter and minimal knots...beauty material! I'd opt to saw it quickly and get on sticks, since I don't want blue stain ruining my mojo.

I also have another option locally to purchase BIG old-growth red oak, which is also relatively straight, clear and ready to taken down. (motivated land owner). Due to my proximity to this material, it is ultimately less expensive, but could be a PITA to deal with since most will be more than my tractor can lift, even though my LT40 wide could buzz through it easily and I can rent a tele handler for a week to deal. I suspect some of these oak logs would yield four or five 8x8's, 20'+ from a single tree!  :o

Any tips or conventional wisdom in helping me make the right decision here? It's a building for my own use/pleasure, I have time to do it to my specifications, yet I'd rather get it up, than talk about it. ;)

If pine is the better choice, I may turn the oak into quarter sawn flooring or something else, as it's just to nice to see it slip away (even though I'm not really into red oak much).

Since my topic is related, I hope it's ok here. I'll gladly move it to Timberframing forum if needed. Thx!
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Offline Dave Shepard

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I'd go with the pine and size accordingly. Its great to work, and is well behaved.  If you don't have a cut list, you can cut large cants and sticker to be resawn later.
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Offline samandothers

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We are looking to build a timberframe or have one built rather.  We need to decide whether to do white pine or mixed oak.  From what we have observed both look good and pine seems to behave better than oak much of the time over the long run or as it dries.  Since the wood timbers are sourced we don't pick the timber used so it is whatever is shipped to the timberframe shop.  This could lead to timbers that may react more, not as straight grained.

Offline Don P

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PA-Walnut, The Timber Construction Manual is a hard copy only as far as I know. It is a code reference much like the AISC steel Construction Manual, the ACI concrete manual, etc, in other words dry reading but full of the technical nuts and bolts of design. It is the engineer's go to guide for post and beam/glulam rather than timberframe construction. Timberframe engineers use the NDS available from awc.org as the basic engineering resource but it is a basic wood engineering reference with no mention of timberframe joinery. At tfguild.org is the red design book and several books on timberframing that might be more useful. Others please chime in here.

Old growth/slow grown ring porous hardwoods like red oak are lower density, less strong but more dimensionally stable than faster "second growth" type trees which are higher density, stronger but move around more. Typically timberfrmers saw out boxed heart timbers getting one timber per log in an attempt to balance the growth stress in the timber. If these trees are massive and lower density and if you can get timbers from well away from the heart it may be worth trying to get some free of heart center timbers out of the logs... watch for bowing away from the heart as you saw. If they saw straight you may have some nice, relatively check free, high grade, stable timbers on your hands. The caveat would be don't push the design strength values, be somewhat conservative if they are truly tight ringed. If they show stress saw boxed heart and get the flooring or siding from the slabs. I've got a gooseneck trailer full of big red oak slabs we'll be sawing into barn siding.

White pine is low density, dimensionally much more stable than oak as a rule, has lower shrinkage and less growth stress. It is a good bit weaker and has bad knot structure, throwing out a complete whorl of branches each year so you have a knot cluster every 2-3 feet. Depending on growing conditions that can be a spray of relatively small insignificant knots or a strength killing cluster of large knots compromising the timber. I'm sounding like a wet blanket, not intentional just keeping it real, the good the bad and the ugly  :P There are few woods I don't like just know their habits... although I mercilessly uprooted a few hawthorns in the woods today  ;D

I do agree with Dave and was thinking the same thing this morning as far as getting things drying. You generally know at least the post and brace dimensions very early in concept, get em on sticks and then keep moving forward from there.