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Lifting this bent

Started by Woodbender, March 02, 2007, 02:06:17 PM

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Woodbender

I've done some preliminary designs on a simple house that we're pretty fond of. Looking over some possible properties.

My first inclination was to have 4 bents w/ 16' bays to make up the length of the house. The overall length of the house is to be 48' and the width will be 30'.  It's basically a ranch style with a 10/12 pitch.

Thinking to save heavy machinery on-site my original plan was to have these 4 bents to have a center prebuilt 12' wide frame to be tilted up and have the rest of the "bent" or primary rafter structure be built around it like a lean-to.  To be repeated at all four primary locations or bents.

I know - I'm a neubie - bear with me.

Reading Tedd Benson's Timber Frame House points out that the frame (or Bent) needs to go right down to and be anchored/strapped to the foundation wall rather than sit on built-up posts in a stick built floor system. In other words - it will have to be lifted and set into these "holes" in my stick built floor deck.  There goes my idea for tilting these Bents into place.

So as long as I now have to use a crane to lift and set these bents into the floor pockets why not build the entire Bent and not just the middle 12' portion?

The weights are about 1900 pounds for the 12' midsection and about 3200 pounds for the entire 30' Bent. (figuring 47 pcf for red oak and 8x8's)  The 30' includes the SIPs so the actual frame is 29'-3".

Would that be over reaching things?  Some of you guys have articulated manlifts or telehandlers or pettibones (is that the right term?).  3200 pounds is a lot to be grunting around and I am not going to do something to get somebody hurt.

I really don't want to shell out $140 an hour for a 17 ton crane let alone how bad they mash up the property.

Can I still tilt these guys up?  If they're assembled on my stick built deck and tilted up they'll slam down into those post pockets won't they?

I can send jpg drawings later.

Peace
Tim Eastman (Woodbender)
Be an example worth following.

Raphael

Quote from: Woodbender on March 02, 2007, 02:06:17 PM
Reading Tedd Benson's Timber Frame House points out that the frame (or Bent) needs to go right down to and be anchored/strapped to the foundation wall rather than sit on built-up posts in a stick built floor system. In other words - it will have to be lifted and set into these "holes" in my stick built floor deck.  There goes my idea for tilting these Bents into place.

  I can name any number of timber framers that have a different opinion on that.  Of the five TF houses I've seen raised since I started researching for my own house the posts in my office and additions are the only posts I've seen that actually penetrate through the decking.  Those posts are lagged to the rim joist(s) for hold down.  I left the subfloor off until the posts were in place to facilitate instalation.
  Three of the others sit directly on the decking (with solid blocking below the subfloor) and a hurricane strap ties them to the rim joist.  Two have just a minimal stub tennon that sits in a hole in the decking to help locate them and one was just placed carefully over marks drawn on the subfloor but they had a really big crane and crew.  I'd suggest stub tenons if doing a hand raising.
  One has none of that but the blocking and all the tying is done with the SIPs.
... he was middle aged,
and the truth hit him like a man with no parachute.
--Godley & Creme

Stihl 066, MS 362 C-M & 24+ feet of Logosol M7 mill

Woodbender

Thanks Raphael.

It makes more sense from a structural engineering standpoint to have these bents fastened right to the sill plate.  It transfers moments and forces right into the foundation.

BUT  I have seen it done countless times in post and beam construction to place them on the floor system with solid blocking underneath the 3/4" t&g ply.  In that particular infill panel system I was familiar with the outside plywood sheathing was the diaphragm and anchoring of the posts to the rim joist and sill etc.

The big unknown I had was the Timber Framed system has the frame itself resisting these moments with the bracing and joints. The outside sheathing (at least in my case) being the SIPs doesn't really add a lot to the shear and diaphragm values.

Which is why I came here to ask you gents.  I thought since the Timber Frame was directly resisting these forces (wind, snow load, twisting etc) then it had to directly transfer them into the foundation rather than have an external skin or rely on a floor system to do that.

I appreciate your answer.

Here's a couple jpgs of what I was talking about. The first one shows the entire width of the Bent. The little lean-to on the side obviously is not part of the Bent - it is merely a sun room.


This second jpg is the middle 12' section I was originally thinking we'd do as a tilt-up and frame the rest of it in piecemeal with ginpole etc. The center 12' section is shown in bold obnoxious green.


Thanks for looking.  I hope my greenhorn questions make sense.
Tim Eastman (Woodbender)
Be an example worth following.

Raphael

  True SIPs (OSB on both faces) work pretty well in that capacity, it depends a lot on the splines and how they are attached, but they do make houses entirely of SIPs (no timbers at all).  Each SIP wall is in essence a big torsion box.

  That's one tall thin bent to tip up but certainly doable, the rule of thumb for hand raisings is one person for every 50# of bent this allows members of the raising crew to step back and pick up pike poles etc. without over straining those that are still holding the bent.  Assuming I could find 38 or 64 willing bodies I'd want to hire an experienced itinerate timber framer to lead the raising.  It's best to have the raising strategy worked out before you start cutting joinery, an itinerate can also give you suggestions on design details that might make the raising and assembly a bit more manageable.
  My primary frame (Jack Sobon's classic timber framed house) went up as 'H' bents, it's a pretty good design idea since it limits the weight that needs to be raised all at once.  We tipped them up with four guys and a Volvo excavator actually only three of us did anything on the first bent.
  For the additions we lifted but the original plan was to tip up slightly and ease the post bottoms down onto the foundation wall through the large open spaces available to us because the subfloor wasn't nailed down.  Then tip up the rest of the way after blocking the post bottoms from slipping free.
... he was middle aged,
and the truth hit him like a man with no parachute.
--Godley & Creme

Stihl 066, MS 362 C-M & 24+ feet of Logosol M7 mill

Woodbender

Quote from: Raphael on March 02, 2007, 06:05:13 PM
  True SIPs (OSB on both faces) work pretty well in that capacity, it depends a lot on the splines and how they are attached, but they do make houses entirely of SIPs (no timbers at all).  Each SIP wall is in essence a big torsion box.

That's true. Many structures are built with double faced OSB which would in fact operate as a composite structural skin/panel.  I was looking at the SIPs being used in Tedd's book which were sheetrock on one face putting the OSB face 4-1/2" away from the frame relying a great deal on the integrity of the long thin screws to transfer any odd loading.  But with the forces being dealt with in the frame itself (then into the foundation) it sounds like a mute point. The screws simply hold the panels to the frame.

I'm finding a lot of UN learning has to be done between my ears. A lot of conventional framing and structural physics relies heavily on an uninterrupted structural skin to act as a diaphragm either on the outside or a designated wall /ceiling on the inside to transfer forces.

QuoteThat's one tall thin bent to tip up but certainly doable, the rule of thumb for hand raisings is one person for every 50# of bent this allows members of the raising crew to step back and pick up pike poles etc. without over straining those that are still holding the bent.

Indeed - this is why I wanted to fling this by you guys. I wasn't entirely comfortable with the idea and wanted more learned opinions by guys who had "been there - done that".

I appreciate the input Raphael. Thanks for the reply.
Tim Eastman (Woodbender)
Be an example worth following.

Thomas-in-Kentucky

Woodbender,

Just to throw out some thoughts... (and some pictures too!)

Post Feet:
The only commercial frame raising I ever watched (they used a crane) raised the whole frame on a flat floor deck.  halfway through the raising, I realized that none of the post bottoms were fastened to the deck yet - they were still moving them around with a mallet!  I guess they attached the post feet later.  The gist - I don't think you need pockets, but by all means, create some temp. pockets or some way to keep the feet from sliding if doing a hand raising.  Also, I poured stainless straps (j-hooked under the first course of rebar) into my foundation and lagged these to my timber posts after everything was raised.  (watch out - drilling through 3/16 stainless is a bear!).

Partial bent raising - by all means possible.  Even though I have a 15 ton crane, at full extension in the horizontal position, it can't lift more than 3,000 pounds!  The 15 ton rating is for the best case scenario (boom nearly vertical, hook directly in front of crane).  This would also be true for excavators and other lifting machines.  Tipping is the main concern.  For this reason (and a few others), a lot of my bents went up in pieces.

***********

Here is a picture of a bit of serendipity that I would purposefully design into my next frame.  I included a few posts in my frame that did not fit within bents.  These were to frame door openings, etc.  It turned out that they were great for holding up girts (and bracing the first lonely bent) until the next bent could be raised.  I didn't plan it this way - it just worked out great.  If I'm not making any sense, see if the picture does!

maybe you can also see the mortises for the shed addition that was raised later.
***********
After the first bents were raised, and some floor joists in place, we put the queen posts (and top plates, where needed) on top of the bents.

then we flew in the rafters and collar ties.

Even though we test assembled it on the ground as one whole bent, I decided to raise this bent in several pieces.  Here is a half bent raised.  Actually, not even a half bent, since the collar tie and rafters aren't on it yet either.  maybe it will give you some ideas.

***********

some other random thoughts...
I would try to put your main rafters up in one piece.  Keeping them whole will do a lot to stiffen your frame.  Even if it means renting machinery.  (but if you can get the bents up, I'll bet you can figure out a safe way to get those rafters up there by hand as well)   In other words, I'd raise your 12' bent w/o the little rafters on it.  Then raise your other bents, then put long rafters across the tops of the partial bents to tie them together. 

The joinery might be simpler if you insert a girt in the main house for the shed rafters to rest upon. (maybe you already have a girt near by).  I wasn't smart enough to figure out how to get the main rafters and shed rafters to hit the same top plate in the same place.  Maybe you've already got that figured out though - I know it has been done - just not by me.  :)

thought I'd add this picture, since I saw no braces in your sunroom design.  This is my timber frame sunroom.  My wife and I jokingly call it the "Yankee Barn homes style sunroom," because it has no corner braces! I decided to omit braces on this shed addition, and rely on the main house, roofing, rafters, stainless foundation strapping, generously gun-stocked corner posts, and SIPs for wind bracing.  This let me put some huge windows in this room.  Stood in it the other day with 40 mph gusts of wind outside and could detect no movement whatsoever.  Disclaimer: Your mileage may vary.



Jim_Rogers

Some clarification of terms or the proper use of terms helps everyone understand, what is what.
A panel that has sheet rock on one side and then foam and then osb is a "curtain wall" panel, according to my supplier.
A SIP is called a sip because it is a Structural Insulated Panel.....
A curtain wall panel is not a structural panel, but it is an insulated panel.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Raphael

Quote from: Jim_Rogers on March 05, 2007, 10:25:09 AM
A panel that has sheet rock on one side and then foam and then osb is a "curtain wall" panel, according to my supplier.
That's how Foard differentiates them, they also supply "Nailbase panels" osb on the outside and just foam facing inward, good for use over T&G ceilings.
  Some suppliers call the drywall/foam/osb panels stress skin panels or SSPs, I tend to use SSPs this way when typing.  Others call all three types SSPs so it's always good to check the terminology with whomever you are talking to.
... he was middle aged,
and the truth hit him like a man with no parachute.
--Godley & Creme

Stihl 066, MS 362 C-M & 24+ feet of Logosol M7 mill

Thehardway

Although there is a lot of good advice given above and they are all more experienced than I am, considering your frame and what you want to do I might think about a little different approach.  Benson, in his book which you have been reading :P, tends to rely heavily on "Bent" style construction.  This is in reality a newer style of timberframing.  It lends itself to assembly with apparratus for lifting large, heavy, preassembled sections.  In some cases it uses SIPS as integrated structural components to resist racking as there are few if any continuous horizontal members.  Although this has become the common practice in mainstream timberframing it is somewhat different from the traditional timberframe style and hardly neccessary or even advisable for what you describe wanting to do and the frame design you present.     

Based on what you have described wanting to do and the drawing you present of your frame, which I like very much, I would urge you to consider framing it in the older non-bent, traditional style method.  The traditional method used posts, tiebeams, top plate and Principle rafter with purlins or common rafters rather than using pre-assembled bents with girts. This method is very clearly presented in Jack Sobons books :P as he is a staunch advocate of it and with many good reasons. Most of the European buildings built centuries ago used this design as did much of the early American timberframe structures.  It is well grounded and was made for hand raising.

The result of this change would mean assembling only the posts and tie beams of the first floor which would then be raised into position one bay at a time and then topped off with a continuous top plate that  ties them all together and creates the plate upon which the rafters will later sit.  This cuts down immensly on the number of people needed and the weight that needs to be lifted. 

You would then install the posts on the second floor along with tiebeams and then put the rafters in place one at a time as you indicated you wished to do.  It would require minimal re-design for timbers and joinery layout but the visual design and basic stucture remain visually the same and perhaps would even be structurally strengthened somewhat. 

I hope I have helped rather than confuse and would welcome others to jump in and correct me if I have missed a reason why this frame would be better constructed in the bent style given your preferred method of raising.

BTW nice drawings and design!

Norwood LM2000 24HP w/28' bed, Hudson Oscar 18" 32' bed, Woodmaster 718 planer,  Kubota L185D, Stihl 029, Husqvarna 550XP

Thomas-in-Kentucky

"Thehardway" has some good advice.  I would definitely read Sobon's book on building a house before committing to a design.  A continuous (or even scarfed) top plate is a really nice element to include in your frame. 

If dramatic open spaces were not a priority, I would build a frame with common rafters and an uninsulated attic.  (being inexperienced and having just built the total opposite of all that myself!!!)  Unless you use fairly expensive SIPs on the roof, you might find yourself going back and putting rafters on top of the purlins!  (which is what I did.)  A few weeks into that process (building a second roof on my first), common rafters started to make a lot of sense to me!

BTW, I really like your current design too.  Looks like you are thinking about the stairway at the right stage of the design process.  Don't forget your plumbing vents - now is the time to think about those as well.  I just started.  :o

-Thomas

Raphael

Quote from: Thomas-in-Kentucky on March 08, 2007, 07:36:33 AM
"Thehardway" has some good advice.  I would definitely read Sobon's book on building a house before committing to a design.  A continuous (or even scarfed) top plate is a really nice element to include in your frame.
I love the top plate scarfs in that book...  They point out the what is ideal isn't the only way to go and sometimes what fits the design, materials available and method of raising takes precedence.

Quote
BTW, I really like your current design too.  Looks like you are thinking about the stairway at the right stage of the design process.  Don't forget your plumbing vents - now is the time to think about those as well.  I just started.  :o

  I thought I'd figured that all out well in advance, and then I went to build my attic stair and realised I'd walking into a knee brace.  :-[  I guess this falls into the measure once, curse twice catagory.  :D

  One thing that has created challenges for us is a lack of available kiln dried framing materials in this area.  I had no idea that I'd be limited to 8' or the shorter precut sticks in 2x4 & 2x6 only.
  The bevel cut 2x8s set into the SSPs on my shed roof have shrunk nearly a half inch since they were installed.  The thing that's really driving me nuts about that is evey time I look out the window I see my father's aborted attempt at building a tree house with my air dried 2x8s hanging from the trunks of a couple perfect timber framing trees and lying below them in the snow. ::)
... he was middle aged,
and the truth hit him like a man with no parachute.
--Godley & Creme

Stihl 066, MS 362 C-M & 24+ feet of Logosol M7 mill

Woodbender

yup - I've ordered a couple of Jack Sobons books at our local library.  That's the nice thing about living near a larger metro, you can still take advantage of their library system yet not have to put up with the big town.

I'm really looking forward to learning something new from what I've read and heard about Jack's books.

If I don't learn something new every day - it's a wasted day.

Thanks again guys - oh - the design has already changed btw.  :D
Tim Eastman (Woodbender)
Be an example worth following.

Engineer

FWIW, all of the posts on my frame sit directly on the sill plate.  We assembled the frame on the finished deck and slid the post bases through holes in the deck.  Jim Rogers was there to see it.  Hard to do without a crane, though - you need to suspend the entire bent so you don't trash the floor system by having the post bases go in at an angle.

Woodbender

Hi Jon

Thanks for the reply.  That's exactly what I was a little ticklish about. Dropping those full bents/posts down into those holes in the floor system. They really have to be carefully dropped in with a controlled crane or something and you can't miss.

The more I hang out here - the more excited I get. You guys are a good influence on me (and I bet that's the first time some of you have ever heard THAT!)

:D  :D
Tim Eastman (Woodbender)
Be an example worth following.

Raphael

I think it may be the second. ;)
I won't mention how many time I've heard the converse.  :D :D
... he was middle aged,
and the truth hit him like a man with no parachute.
--Godley & Creme

Stihl 066, MS 362 C-M & 24+ feet of Logosol M7 mill

Don P

 :D :D, I ain't sayin nuthin  :-X.

I'm levering the bent into a hole here while Brandon directs the crane. I think Mike just had his hands in his pockets  :D


One of the 5/8 furring strips is attached to the post to space the sips for drywall.
I just picked up a few logs over there today, the drywall finishing has begun.

Jim_Rogers

I agree with "Thehardway" comments to a point.
First the rafter to post design, in my opinion, is not the best. As mentioned to have the sills at one level going one way, the ties on another level going the other way with the plates on top opposite the ties makes a grid of layers that holds the building together and makes it very strong.

However, I you have the available timber to make your posts from sill to plate in one piece that would be good, or better than placing second floor posts on top of first floor posts or ties, similar to platform framing.

You should review your design, and consider making a model of it to understand where every piece goes as well as how it all goes together.

With proper planning you can lever a bent post into a pocket or slide one in, it really depends on the length of the bottom tenon or where the post will sit.

Do a search here in this section or check out my gallery for photos of post to foundation connections. There is some info here for you to look at....

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

pegs1

Just some thoughts from a timber framer/GC.

We have raised a bent frame with an 8000 lb terex rough terrain forklift.   The frame was 24' wide and about 30 ft at the peak.   It was a little hairy but we got it up.   I think we will be modifying the forklift in the future to raise a frame with a cable winch straight up to the location of the bent.   By that I mean we drag the frame across the floor going vertical as opposed to trying to raise the frame with the forklift with the ends of the post being where they will go to start with.

That way the forklift will be at is max height and load capacity when we start and we don't have to move it around as the bent goes up.   

Regarding SIPS, we use them on almost every house.   We have done a few stick framed enclosures, but not many.

I am a firm believer in SIPS, both for thier insulation value as well as thier strength. 

We typically put our frames right on the deck, not through it.   There are blocks or posts under the plywood decking depending on the foundation type and width.   We use GRK RSS structural screws from below to screw the posts to the floor.   Using SIPS there also is a sill plate which is screwed to the deck/trusses around the perimeter.   We typically put more screws in it that an average stick frame house would have because it is part of the strength of the structure.  Then the SIPS are fitted over the sills and screwed to the post every 2 -3 ft and to the sill inside and out every 12".   On an average house there are about 30,000 screws in the SIPS panels/splines/bucks which are also caulked and foamed.

There has been independent research done regarding what structural integrity is "added" to a timber frame structure using SIPS.  They not only reinforce the wall structure but also transfer loads across rafters/purlins and help to mitigate the effects of torsion and wind loads on the frame.

In addition we use 4" X 5/8" plywood shims/strapping around all of the exterior on every timber to allow for sheetrock after the structure is enclosed.   When the shims are installed they run across our joinery so they also add to the strength of the joints and help to tie the frame together.

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