Joints in Roof Rafters and Studs?

[archis]

One of my WACIs (Wild and Crazy Idea) is to build modular components to simplify small shed/shelter construction in remote locations where it's not feasable to get a vehicle. Locations where supplies/tools need to be hiked or small boated in.

I'd like to work with standard dimensional lumber and it would be nice to have the components to be 4' or less for portabilty. Since I'm not a seasoned woodworker nor structural engineer, I need advice on the feasbility of joints in wall studs and rafters.

Is it feasable to joint a 2x6 roof rafter or a 2x4 wall stud? If so how would you do it?

Thanks,
Jim

[meatbal80]

I have been thinking along the same lines for a shed i need to get and wanted to use the bot to make. Every time i look at making joints to join walls to other walls or to the roof it seems to be just a waste of time and effort. The thing i have been thinking of has been to use .5 or .75 ply and making plates to make assembly easy. i havent had a chance to draw anything up just yet but will keep this thread in mind when i do.

[archis]

One of my ideas was to make a puzzle or some other type of joint in the rafter and then glue/screw an OSB plate over the joint.

[wberminio]

Go to http://projects.100kgarages.com look under dog house

Also http://www.shopbottools.com/mPeople/pressmedia.htm
look down at Unique houses to Haiti article

Bill young and others have been working on CNC cut parts for structures-even houses.
Do a search you'll find plenty of ideas

[navigator7]

One of my WACIs (Wild and Crazy Idea) is to build modular components to simplify small shed/shelter construction in remote locations where it's not feasable to get a vehicle.

Since I'm not a seasoned woodworker nor structural engineer, I need advice on the feasbility of joints in wall studs and rafters.

Is it feasable to joint a 2x6 roof rafter or a 2x4 wall stud? If so how would you do it?

Thanks,
Jim

I'm a builder with lots of unconventional experience.
Everything is a trade off.
Current building practice with dimensional lumber is pretty darn good.
What you are asking is at least 3 times the work over normal building.

Conventional building relies on compression.
2x6 walls with a bottom and double top plate can handle enormous loads.

OSB sheeting over the studs and trusses ties everything together . When done properly from the ground up everything is very strong.

Joining wood together like you suggest is what we would call "sistering".
Any joints would need to work well in compression.
A butt joint might be the best and simplest.
Your idea may work but require twice the wood to achieve the same design.

I don't see OSB as a good substitute for studs but it works great in TGI's.

3/4 marine grade plywood ripped to 5.5" x 4' long and glued and screwed on site might do the trick for studs and trusses.

Concrete block is modular as well as mortar.

If you need a permit .... "unconventional" makes the building dept freak. good luck.


ICF panels like Quadlock or Superforms might be your best bet.
Kids can build a form but getting the concrete in is a PIA.

[archis]

Erminio,

I think all of those designs are out of ply, my question is about joints in dimensional lumber.

[archis]

Chuck,

I get the butt joint working well for studs where compression is along the length of the board. It seems to me that for a rafter where the load is closer to perpendicular to the length of the board, a finger type joint would me more sense.

The OSB sistering on rafters would serve two purposes, added strength for the perpendicular load and extra protection to prevent the joint from lateral separtion.

As for block and mortar, the idea is lightweight components that can be packed in over may trips. I could probably pack a single cinderblock about 1/4 mile cross country and that would be my day:)

[wberminio]

You might do well looking into modifying traditional post and beam joinery.
Which is basically,mortice and tenon joinery.
I just looked at a 200+ year old barn. Each joint was marked with Roman numerals and locked in with a wooden peg.
The only section that is damaged ofter all these years is from water damage.

Also look into traditional Japanese joinery.The old Samurai houses used interesting joints to make the best of limited wood resources.
They maybe modified to cut on the Bot.

In the end it seam that a bucket of nails and a hammer or screws and a cordless drill might do the job.
I think,even the samurai would of used a Shopbot and a Makita drill-if they had one.:)

[Gary Campbell]

Jim...
The majority of code approved contruction joints are like Chuck says, compression. In other words they are stacked and then nailed to prevent movement. All other components are engineered. In other words, they have been either designed or tested and approved by a licensed stuctural engineer that signs off on the method or material.

Take a look at what Bill Young and Robert Bridges are doing with ShopBot cut small structures. Search MOMA. There is a lot of info in the bowels of this forum.

Realize that the code requirements for a doghouse or garden shed (if any) may be much different than for a housing structure.

[frank134]

go to the big box store ( i know that a bad name ) like HD . they have metal clip to join stud and the like together. really simple to use.

[ken_rychlik]

If you build it truss style for the roof framing, you could use shorter pieces. There would be webbing that would intersect the joint, giving the compression load requirement. At these joints, most buliders use the mending plates to tie them together, but plywood has worked for years also.

[archis]

Ken,

Great idea, thanks!

Here's a site for the plywood designs:

http://www.physicaldesignco.com/

[ken_rychlik]

One more thing to keep in mind. Building codes allow for finger jointed studs on interior walls only in Texas. They are not allowed for an outer wall. You local codes may vary, but is something you should check out.

[michael_schwartz]

I would do a bit of research into the field of timber framing if your interested in structural wood joinery. I would also take a look at Japanese examples as well as they use some really interesting joinery. On a smaller scale using a shopbot to cut such joinery might be an interesting possibility. However full scale joinery on an 8x8 or 10x10 timber would of course present a number of difficulties and that would be the time to get out a large circularsaw and chain mortiser.

If you had to build a structure with nothing more than what you could carry in to the woods, a look at historic methods may give you the answer your after. After all 200 years ago if you were going to set off to build a house in the woods, you were probably limited to what you could carry on a horse.

Of course the more economical/modern solution may be to work with an engineer to design structural brackets/connectors to meet your needs.

Hopefully codes aren't too big of an issue where your planning to build.

[kevin]

I'am in a remote area they don't care about looks .Just price .
I don't offer advise but you have to come up with a speciality item for which there is no competion
Or go door knocking offering cnc sevice

I live in a semi remote area .We have box stores 1 hr drive they have perfab sheds you name the size .Plus the'll ship to Labadour I hr flight
Mined you there is a huge boom in Labadour 1 billion dollar mine expansion funded by the China
Plus down the road from me there are two major project over a billon dollars each one now and next year

[bill.young]

Hey Jim,

I'm not much help with lumber though we have tested a few joinery methods without much success. The biggest problem was trying to hold construction lumber flat and straight to cut it...we just couldn't find anything locally that was consistently straight enough to cut accurately. The best we could find was Structural grade yellow pine, but that still required some picking and is only available here in wider boards that would have to be cut to width first for stud...it may be different where you are.

I have worked quite a bit on buildings using plywood, though. You've found the physicaldesignco site and I'm sure the MoMA house that we worked on with those guys. It was amazingly strong and went together quick and might be an option. The Shelter2.0 project also breaks down into small pieces that would be easy to carry, although the floor and wall panels are in the 3'x7' range which might be a haul if you had to carry them far.

Our newest projects have been laminated plywood versions of timberframe construction, with the joinery designed and cut into the layers of the pieces (Ted calls it "plyberframe construction" which has a nice ring to it!). There's a video on youTube of our first building http://www.youtube.com/watch?v=KtW0jzPHnD4, but since then we've developed a simple method for making the laminations sort of "self clamping" during glueup, so that the pieces could be cut offsite and easily glued into finished parts on the jobsite without a boatload of clamps. All the parts would be small enough to carry to the jobsite, to be glued up into big beams.

And don't miss Rob Bell's amazing geometric structures for inspiration...they are very cool.

http://www.flickr.com/photos/zomadic/ (http://www.flickr.com/photos/zomadic/)

Bill

[navigator7]

Chuck,

I get the butt joint working well for studs where compression is along the length of the board. It seems to me that for a rafter where the load is closer to perpendicular to the length of the board, a finger type joint would me more sense.



I understand your conundrum. ;-)
You might want to look at something called a Flat Truss or a Vaulted Parallel Chord truss. It consists of many
2x4's finger jointed into one very strong truss assembly.
I am using a flat truss in my shop I have under construction for a second story floor. A 25' span with very significant floor loading ability.
No metal plates....just glued finger joints.

http://www.classictruss.com/art/wodd_truss_types_examples.gif

http://www.classictruss.com/roof_truss_facts.asp

These types of structures are normally engineered, cut , glued and fabricated at a plant. Engineering follows it all the way to permitting.

If you are a botter ....it changes the equation. The goal is to make many trips with lighter loads as conventional methods are out.
The question is, then, can you cut a suitable finger joints, package and ship the joints without too much damage, create a parallel and square fixture on site, glue and clamp and then lift the resultant structure into place?
Rain snow and cold, dust dirt and damage?

I'd come up with a design that suits you and then figure out a way to do a destructive test. Break it. As the Building Dept sounds like it will be out of the loop.....you are the beaver. (BTW...I like beavers. They have more sense than most building inspectors ;-)
http://www.jetew.com/Beaver.jpg

[wberminio]

Way too cool Bill!

[navigator7]

Way too cool Bill!

Dittos!

No tool bags.
No compressor.
No power tools.

Did anybody wince when that guy stuck his fingers under the column?
Yowsser...lol.

Waterproof Resorcinol Glue, Bill?

[bill.young]

Thanks Erminio, though I can't take too much of the credit. All these projects were collaborations with others, most with my buddy Robert Bridges. Fortunately both of us are willing to try out ideas when they're still pretty half-baked, which sometimes yields some pretty neat results but also can make for a pretty big scrap pile!

Happy Holidays,
Bill

[bill.young]

We didn't want to have to generate all the clamping pressure that resourcenol glue needs so the original prototypes and the building in the video were glued with gorilla glue to make any squeezeout in mortises easy to clean up. As we refined the process squeezeout became less of a problem, so now we use Titebond 2 and are happy with it so far.

[archis]

Chuck, thanks for the info on the trusses and the Darwin beaver photo.

Bill, Are the moma cut files available anywhere? This looks like something I would like to mess around with if they are freely available. BTW, I used to fish out of Willis Wharf when I was a kid, nice spot.

[bill.young]

Hey Jim,

The files for the New Orleans house are not available, but they did a small cabin at MIT as a first test. I think the dxf files are available for that...I'll look around.

Bill

P.s. so you're the one that caught all the big flounder!

[archis]

If you could find that cabin file that would be great. I get how the sheathing goes on but still don't get how structural sections work.

It looks like the Shelter 2.0 is made out of OSB, will that work for a Moma style structure?

[wberminio]

Check out this post
http://www.shopbotblog.com/index.php/category/get-physical

This site

http://www.physicaldesignco.com/get%20physical_3D-design-templates.html

[bill.young]

We have done some prototyping in OSB, but don't use it in any of our structures...the quality is so poor that we only use OSB for the shipping crates. Instead we're using an underlayment material called Advantech by Huber that's radially-spun and has a 50 year warranty when used as a subfloor. It's strong, seems to hold up well, and doesn't curl and cup like plywood. It's also one of the materials that was considered for the MoMA house, which was eventually cut from plywood donated by Georgia Pacific.

[archis]

The templates that I have found on the physical design site have been skethup files, not cut pattern files. Did I miss them?

Bill, How expensive is the Advantech product?

[wberminio]

Jim
It is possible to receive the cut files
Contact Physical Design

[archis]

Erminio,

It's hard to understand how they work at physical design. The article you sent helped a little. Do they charge for the service of converting the sketchup model into a cut files? I emailed them this morning to try and get more information.

Thanks,
Jim

[wberminio]

I believe there is a cost
Idea seems to be that you can modify your design in Sketch Up
and they will supply the updated cut files.
You can cut them yourself or get them cut.
I was working on getting approved by them to become a fabicator-but got side tracked.
I think I look into it again.

I'm sure Dan @ Physical Design will get back to you soon

[bill.young]

Information on the first MIT cabin can be found in the MIT Digital Design Fabrication Group at http://ddf.mit.edu/projects/CABIN/index.html. If you follow the "Full Scale Construction" link you can find the dxf files of the parts.

[archis]

Thanks for the info Bill. The drawing link is 404ing but I sent the webmaster an email asking if they are still making the drawings available.

[bill.young]

Sorry about that. It used to work...guess I should have tested it!

[archis]

It's MIT, I wouldn't have tested it:)

[navigator7]

One of my WACIs (Wild and Crazy Idea) is to build modular components to simplify small shed/shelter construction in remote locations where it's not feasable to get a vehicle. Locations where supplies/tools need to be hiked or small boated in.

I wonder if your could refine the parameters?
Maybe make a challenge?

I brought your request up with the builders I work with and the initial reaction was why?

Current building practices are very good. (Except permitting)
As the day wore on they kept coming up with ideas and asking more questions.
All I knew was something about water and 4' limit.

We thought...building the house out of foam sandwiched between layers of carbon fibre roof and all.

Building a barge of foam to carry all the building material in one shot would be good....as it is pretty east to drag a 40 ' TGI or 16' 2x6's without too much effort.

Maybe even building a dragline or highline to the building site?

It's intriguing to think of building a structure a different way!

For example.... imagine building a shed with Bill's linkers....but with places to wind carbon fiber.
I can imagine the wimpiest truss system becoming mega strong with proper windings of carbon fibre placed in tension and sprayed with resin.

Another choice is build the structure with lifting in mind and helicopter it to the location.


Price Quality Speed

(Pick any two) ;-)

[archis]

Chuck,

To be honest the "why" is a little bit self serving. I have property in Canada on a lake that consists of two parcels. One is common with other owners and can contain a dock and storage shed. The parcel that can be built upon is about two miles away via water. Furthermore, the building site consists of about a 35' climb up a very steep (2 feet and 2 hands) climb from the lakefront. There are no public ramps on the lake so I use my 12' porta-bote to get to the building site.

Now I could go the more conventional route of hiring someone with a barge who knows someone on the lake for a launch site, or drive a truck over the ice in winter. Either of these approaches would probably require clearing some trees to get larger building components to the site. I like the site in it's pristine condition and want to have a shelter there with minimal impact to the environment. By law in Ontario, I can build up to around with 104 sq/ft without any permitting. In reality, the site is so secluded, I could build a 7/11 there and they wouldn't know :)

After thinking it through, further research and reading Bills comments, I think the Moma style or Shelter 2.0 is the way to go. Bill and friends have
really got some great ideas.

On a less self serving note, I can't be the only person in the world who has hike, boated, skied or whatever to a remote site and thought "Man I would like to spend some time here".

Sorry for the long winded Reply.

Jim.

P.S Yes I could camp but I'm scared of bears!

[navigator7]

Chuck,

To be honest the "why" is a little bit self serving. The parcel that can be built upon is about two miles away via water. Furthermore, the building site consists of about a 35' climb up a very steep (2 feet and 2 hands) climb from the lakefront. There are no public ramps on the lake so I use my 12' porta-bote to get to the building site.
On a less self serving note, I can't be the only person in the world who has hike, boated, skied or whatever to a remote site and thought "Man I would like to spend some time here".

Sorry for the long winded Reply.

Jim.

P.S Yes I could camp but I'm scared of bears!

Shelter 2.0 is a better option over conventional building especially within the parameters.

If you did build a 7/11....You need a couple of stiff legs and fabricate a logging highline.
Some cable, snatch blocks, pelican hooks, shackles, winches, batteries, inverter, solar power.
Don't use trees unless they are back stayed.

Flexifloats can transport all the supplies in one trip and provide a terrific dock!
http://www.flexifloat.com/(S(03b0b5qccdovjqinya2mhmm1))/images/home/float.gif
Your portaboat might make a suitable tug without any wind.

As a property owner in some wild country....human voices scare me more than bears.
;-)

[archis]

After due consideration, the shelter 2.0 won out over the 7/11.

Never heard of flexifloats, thanks for the tip.