board length

Jumpinfrog · November 07, 2008, 12:34:08 PM

I am building the one story 20 x 30 cottage and I am planning to build a loft over the bedroom and bathroom. I am planning to double up 2x12x20's @ 48" and built up 2x8's for the collar ties in the cathedral ceiling area. Since I have started, I have watched Craigslist like a hawk and have got some terrific deals on tools, blocks, adhesive, windows and doors

. This however was not one of them. I found a guy selling leftover DF 2x12x20 for super cheap, looked straight, not too split on the ends and I bought all 9 boards. As it turned out the boards were only 19' 9" long

I should have measured them

.
The question is, can I use them to span the 20' distance bearing on the 2x6 top plates and tie into the rafters with the 10/12 pitch? I would be 1 & 1/2" short on each end. I know I would have to have enough area to nail to the rafter.
Are these usable? I will stick to the lumberyard after this

MountainDon · November 07, 2008, 01:05:41 PM

The length would not be a problem. The real question is what is the grade of those 2x12 DF's? I believe the plan calls for select structural grade for that 20 foot span. I could be wrong... I'm John will check in and verify or discredit.

FYI, those would be called planks. Boards are usually 1" or less in thickness.

November 07, 2008, 01:56:03 PM

Oops, 2x12x20's @ 24"spacing

not@ 48", (per the span calculator). The planks are DF no. 1 & 2, not select structural. I tried to calculate this part on my own because there is no loft in this plan. If I double them up @ 24", 14 total planks for 12' loft and also nail to the rafters every 24" with 2x6 T&G on top, this should be a solid option? I know it will not look as nice as wider spacing but thats ok. I will add 5 more planks, I just wanted to make use of these 9 low cost 19'-9" as well. The calculator has it at DF No 1 2x12x20 at 16" so dbl at 32", but if I do it at 24", I will be able to tie into rafters?
Thanks for the FYI- with all that I've read on this site, I should have picked up on that by now!

MountainDon · November 07, 2008, 05:52:14 PM

If the lumber is stamped #1 & #2 on the same piece, then when you run calculations I believe the proper and conservative thing to do is to run the numbers as #2, not as #1.

Using the AWC calculator, at 12"OC that just makes the cut, with L/360 40# live and 10# dead load = 20'11" span maximum. However with it being a loft you can use 30# live for a calc of 23'4" So doubled x12 24"OC would swewm to make the cut as well.

We'll see what John has to say about this though.

John Raabe · November 08, 2008, 09:55:04 AM

You are right, the one-story plan does not have a loft plan as the 1.5 story does. That said, if you well nail off the roof rafters @ 24" o/c to the loft joists (doubled 2x12 @ 24" o/c) you will have a solid support for your decking and the rafter tie at the same time. (I don't think you will not need a collar tie if the rafters are 2x10 or 2x12). Not only is the loft floor loading 30 psf (to a main floor 40) but the sides of the loft for 5' on each end are lightly loaded and usable mostly as storage. Grades of #1 and #2 should be fine - just don't put two lower grade ones together.

I am on the road until the 15th so do not have access to the plan myself. So take me with a grain or two of salt

, but the above should be fine.

November 08, 2008, 10:34:59 AM

The cats away -- the mice can play...

John Raabe · November 08, 2008, 05:32:31 PM

Here's where we're playing...

Sedona, AZ airport mesa at sunset.

Actually, I'm now in a student coffee shop in Flagstaff.

MountainDon · November 08, 2008, 05:36:31 PM

The great SW

glenn kangiser · November 08, 2008, 05:36:43 PM

A very cool place to play, John.

We spent quite a bit of time in that area. Jerome, Az is cool also as well as the Gold King mine there. Below in Verde Valley are cool ruins - Montezuma Castle and well, Tuzigoot (sp?) etc.. Tons of neat stuff. Have fun.

http://www.goldkingmineghosttown.com/

November 08, 2008, 05:42:38 PM

anywhere in NM on the list of travel spots?

I'm heading back to the Jemez after dinner, my cold is getting better.

John Raabe · November 09, 2008, 08:36:59 AM

Thanks for the suggestions. We will probably spend a day in the Verde valley (Camp Verde) and I'll check out the suggestions, Glenn.

NM will have to wait for another trip as we have folks to visit further south in AZ.

glenn kangiser · November 09, 2008, 10:39:58 AM

Always too much to do in that area. Jerome is a copper mining town on the side of Mingus Mountain. A bunch of dynamite went off when a steam shovel hit it and blew up. The jail slid down the hill to the next street. It's a very cool place just up from Cottonwood. Artists - antiques and my favorite - the Gold King Mine and working museum, with antique engines running a sawmill - working model "T" truck - tons of stuff. I used to fly in and rent a car to go there.

Wherever you end up -- have a good trip.

Jumpinfrog · November 10, 2008, 01:09:57 PM

Thanks for weighing in while enjoying your vacation. Nice picture, I can imagine one of those desert sunsets! I appreciated the help on figuring up the loft space. When you mentioned about not having to have collar ties with using larger rafters (2x10 or 2x12), would that mean with the 12 feet of ties/deck support, I could leave the cathedral portion wide open with no ties(built up beams)? I will of course take the answer with a grain of salt!

glenn kangiser · November 10, 2008, 01:31:27 PM

If you mean total open area with no ties or beams, frog, I don't think so. I think beams or ties are still required every 4 feet....til John gets here with a better answer.

November 10, 2008, 01:35:08 PM

I think that 4' number would depend on plate width and snow load.

Jumpinfrog · November 10, 2008, 01:57:37 PM

Thanks guys. Maybe it was whether or not collar ties in addition to the 2x12 deck support and ties every 4' in the cathedral to the end?

Putting in the built up ties is no problem, My wife read the post and liked the idea of an open ceiling

, so I will find out.

rwanders · November 10, 2008, 02:35:23 PM

If you used a ridge beam, properly supported, I think you could go without collar ties altogether----However, John Raabe or MountainDon would be better judges than I

glenn kangiser · November 10, 2008, 02:47:56 PM

Yup - a Ridge beam is a different story. It takes the load to the foundation off the end or a post bearing on a footing - then nothing internal is needed.

MountainDon · November 10, 2008, 03:08:15 PM

A proper ridge beam would need to be engineered [$$} along with the downward load path, from beam to foundation. If you are in an area with code inspections they would want to see the engineers stamp for sure.

However, use of a ridge beam would sure open up the interior possibilities.

Jumpinfrog · November 10, 2008, 03:33:29 PM

Ahhhh,
Those built up collar ties every 4' are sounding just right!!

No thoughts of ridge beams here. I will be telling the better half to stay on the original path! Sorry honey

Thanks though for some different ideas.

November 12, 2008, 06:51:23 PM

Ties at the bottom of the rafers (I use built-up double ties to look "beam-like") at every other rafter pair (4' o/c) is a time proven standard practice for roof framing. There may be some special loading conditions where an engineering review may be required by your inspector. Such a framing system has a non-structural ridge board rather than a structural ridge beam. The forces are triangulated and rafter and beam tied together at the plate with strong nailing.

When you make the ridge carry 1/2 the rafter load as a beam, then you do not have to triangulate the framing to keep the walls from spreading. All the forces are downward. This beam must be both substantial and calculated for the specific span length, snow and wind loads as well as the weight of the roof and framing. The advantage, as mentioned, is that the roof can be totally open on the inside.