Appropriate First Project?

Hi Everyone,
So, I've read the books, I've gone over this plan a few dozen times, and I think I'm ready to tackle my first timber frame building. I've got a ready supply of rock maple, and I'm hoping you all can lend me some experience and tell me if my cabin plan is to ambitious for a first project. Don't hold back folks, if this is an ill conceived disaster just tell me I'm an idiot.
Here's a link to the plan
It's 24' x 24' on a concrete slab, and the front sill is missing so when I tackle the house, it can be re-purposed into a garage.
All input is welcome, and I look forward to hearing from you.

Hi Devin,

It looks like you saved this in a pro version? I am not sure if anyone with the free version can open this file.

Regards,

jay

Huh, didn't know you couldn't open pro version files with the free version. I'll re-post it shortly, thanks for the heads up.

You can open the pro with free. Unless its a layout file.

Current free and pro is v2013.

Hi Mike,

I have tried again to no avail in opening Devin's Sketchup file. I get a warning that states:

"you have version 8.0.16846.
you need version 13.0.3689."

We only have one 'pro license' and that is in the office shop computer, everyone else has a free version. I have tried updating, but that is a pro version you must pay for. I would love some guidance, if I am doing something incorrect?

Regards,

jay

Hi Mike and Devin,

I figured it all out...

I needed to upgrade to "Sketchup Make" and now have the file open for review.

I will let you know a response soon Devin. Would you please send me an email with you contact info @ tosatomo@gmail.com.

Regards,

jay

Jay,
I've sent an email your way, thank you for your assistance.
Here's a version 8 copy of the file for anyone else interested.

How about a few jpg screenshots for those of us too stubborn (or stupid?) to get sketchup?

[img]https://plus.google.com/u/0/photos?pid=5903158658512214850&oid=110695973610279379923[/img]

This is Devin's current design, sorry that it is not posting, don't understand why?

cant see it. Not how you link to things on google plus.

Also to direct link to an image here, the address has to end with a file extension (.jpg, .gif, etc.)

So right click on the image, click on the option 'copy image location' or whatever is closest to that on your browser. then paste that.

It seems to be working now???

The method I used earlier is the same one I have used in the past, I'm not clear why it didn't work exactly? It is a .jpg file and it is in the same index of my online photos that I always have used for posting pictures here, just did not work last time?

Regards,

jay

Google changes things all the time. They just changed google plus and how it works.

hence the problem, i suspect.

thanks for the pic

Hey yo jay, did I ever send you the drawings for the barns I will build this fall?

As for this design, looks straightforward, simple, not much going on that would cause concern. The ridge is directly posted to the ground, that's good and simplifies the tie joinery -you wan't have outward thrust, actually those principle rafters sticking past will push IN on the walls.

What kind of roof covering will you use? I myself am a fan of common rafters rather than common purlins, but that's just my background. Id use those posts to support big heavy purlins and hang rafter from them. Then the frame would really be the prototypical west Germanic frame.

One aspect I see is how the common purling cant over the end rafters, that is a lot of over hand and either the rafters are substantially cut or the purlins or both. I would look at lodging the purlins on top of the rafters. Saving the structure of the rafter.

The long purlin overhangs are for coverage of the infill strawbales and earthen plaster over that. The long run plan is for this to be effectively a two car garage/ell connecting the house to the "barn". Would common rafters be more appropriate? The roof system will probably be tongue and groove covered in foam, topped with steel.

The purlin system will work well for this application. If using rafters you could extend the ridge and plates to carry the outside rafters, but I would prefer purlins. My point is the purlin to rafter connection, if you lodge the purling on top of the rafters the building will suffer no loss of strength, as show in the depiction.

Here is a video showing lodged purlins on three of the four bents, this building has no major over hang at the gable ends. By-pass purlins on bent three, bent one has tusk tenons. These have daps to hold the purling others I have done have no daps and are a great time saver.
http://www.youtube.com/watch?v=NLD8-CEmTLE

I see, in lieu of fully seating the purlins into the rafters, run across the top of them with a shallower half-lap?. My concern was the large overhang levering the center up. I think I understand, but my mastery of the terminology is poor. I'll post a picture shortly, please bear with me.

Tim,
Is this along the lines of what you are suggesting?

Yes. by pass and shallow daps or none at all.

Here's an update/slight retooling. I've incorporated the bypass purlins on TIMBEAL's recommendation, and entirely removed the sills, as eventually I'm hoping to expand to the left and right, and the front will eventually have two overhead doors, so it made little sense to have a sill along only one wall.

removing sills seems to be common today, where the posts are instead bolted down to the foundation below some how.
But I've never been a fan. I'd sooner put in a framed floor. It's not that hard to make a wood floor strong enough to support a truck, lots of bans around here have them.

How far apart are the purlins?
It is very common practice on granaries in the southern Germanic areas to have a purlin roof, and it's also common in Sweden. The granaries of Switzerland and Austria are very closely related to the log houses of Norway and Sweden. I've seen lots of granaries in the Canton of Bern framed like this -the purlins supported only by the walls and spaced about 4 feet apart. This supports a board roof, onto which wood shingles are nailed (today its often ceramic tiles)

The purlins are 24" oc. I agree with you on the sills, I'd rather have them, but its a compromise for time and cost so I can afford to put more of the features I want into the house later. It's unfortunate, but alas, thus is life, eh?

From my limited experience (one house built) I would strongly advise the use of sills. I didn't and have regretted the decision more than once. For a four post frame it might not be useful, but the moment you need to align multiple posts (ie. 3 or more in a row) the sill saves a lot of effort. You could always still pour a slab, and make a ramp over each of the sills for the entrance... although this would preclude ever pushing a vehicle into or out of the garage!

If you're planning on raising as bents, bear in mind that your centre posts create a hinge point for the girts. Either you have to size the joints so that they can take the lateral forces and lift the girts, or you have to lift all three posts simultaneously ensuring that the force is distributed evenly... again... this is the voice of (recent) experience! :-)

Hi everybody,
I'm having some questions about the rafter and purlin spacing and sizing, and am hoping someone can point me at a resource and walk me through the process.
Thanks,
Devin

What's the snow load for your area?

Our ground snow load is 40psf.

Great, now we need to understand the sizes and spacing.

I have measured your version 8 drawing. I see that the purlins are 4x4's and are 2' on center in the rafter plane but 1' 9 3/4" on center in the run of the rafter. And the unsupported span of 11'. Is that right?

I'll assume it is. And that would give the area each purlin is supporting to be 19.9375 sqft, round up we'll call it 20 sqft.
20 sqft x 40 lbs live load and we'll assume a 10 lbs dead load for the future roofing materials for a combined load of 50 lbs per sqft to be 1000 lbs. (20 x 50 = 1000).

Next we need to understand what type of wood the purlins will be made out of. Your first post says "rock maple". Is that correct?

Jim Rogers

Jim,
Thanks for spelling the math out for me, I'm starting to see how it comes together.
The rock maple supply I have is "free" but the more I dig into it the less free it gets, with trucking and sawing; its almost as costly as buying EWP from the mill down the road from me, and I'm within their free delivery range, so they'll drop it on the property with no charge.
Long story short, I haven't settled it yet, but it looks like either EWP or rock maple. As always, any advice is appreciated.
Devin

You'll be a happier man with EWP.

You'll have no bones left after working with hard maple.

Well, since you asked, you will enjoy working pine. What you will experience working rock maple I can't say for sure. Probably not much joy.

I also understand maple gets harder as it ages, and this stuff's been sitting in the barn since the owner had a heart attack 7 or 8 years ago. Just another reason I'm probably gonna go with the pine from the sawmill

Dry maple is much worse than green. I'm working some white oak right now that's been sawn for less than two years, and I've broken everything but my boring machine. I can't imagine working year old maple. Maybe with power tools.

Hi Devin,

Sorry, we have now 6 frame going on so I have been tardy in my responses. Dave S. is more than correct. I had no idea that the maple you were considering was not fresh from the mill. It would be more than an arduous task to frame with it. I also do not encourage folks to frame with the Maples and Birches with out some years of experience under their belts. Beautiful wood, however, one must truly know the timber craft and the species like this to work well with it.

You will love the White Pine. It is a marvelous species to frame in, especially for a your first project.

I have worked with maple, I'm going to use a bit of fresh sugar maple on my next barn just because there are a few trees standing where the building needs to go. It's not really that fun.

But I can take you to a super nice Swiss style forebay barn a few miles from me, the lower beams are ALL sugar maple (probably for the same reason, the trees stood where the barn needed to go)

After having worked with white pine, I seek it out for everything now. I've become a pine man.

Thanks for all the replies everybody,
After the overwhelming response, I'll definitely be going with the pine. Have run all the numbers, it works out to only a few hundred dollars difference, and I think we'll just call that my salary for labor.

Pine is a nice wood to work. Another favorite of mine is popple, similar workability as white pine but fewer knots. Haven't worked it in a dry state, but a 2" mortice is no problem with my boring machines in green wood.

I would encourage you to try a few different species, it builds character, in you and the building.

Ok so we'll figure the sizes based on using EWP.

Jim Rogers

Jim,
Thanks for refocusing the thread. Sorry about the delay, I've been traveling for work.

I ran the numbers through an online beam sizing calculator as a 4x4 EWP spanning 11' with a 1000 load and it failed in bending and deflection.
You need a large timber or some other solution like closer spacing.

To get a timber that will pass at this spacing and span you're going to need at least a 4x7.

Jim Rogers

Hi Devine,

Here is a design of a Pavillion we will be installing at a pool facility in Fairfax, VA just outside of Washington DC in September. It is 4.8m x 7.2m (16'x24') with a 4/10 pitch (22 degree) common rafter system of 100mm 100mm (4"x4")rafters that are a 600mm (24") on center, and span approximately 2.4m (8')

Your design just needs a little tweaking to work, even with square rafter stock in the smaller dimensions (4x4 to 5x5.) I would have a PE check out the final design if you are not certain of your math. There is a lot that can be considered on roof loads, including pitch, and deck diaphragm configuration that can influence load capabilities, such as double layering of plywood (should you go the sheet good way) spline, toggle, or t&G board stock.

Regards,

jay