Author Topic: Timber frame barn plan questions (Read 919 times)

cib · « **on:** October 10, 2019, 08:08:13 AM »

I'm near the Salem VA area. The plans were drawn up for a 24x27 foot barn but things have changed and I'm considering expanding to a 24x30-32 foot. I'll pour a full cement slab for the floor.

The posts are 8x8, I used 8x8 for the plate as well in the design but I need input if that's the correct sizing. I don't have the rafters drawn in but 4x6 rafters on 4' centers. the supports for the plates are 4x5 I forgot to add my lateral 4x5 braces in the drawing.

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Don P · « **Reply #1 on:** October 10, 2019, 04:56:15 PM »

Hey cib, I'm just down the road from you in Grayson County. I'm not following the 4x5 plate supports, bent tie braces? Width of center of bent? Width of side sheds? Center bay span? Species and grade? Assuming 30psf snow+10psf dead load? Ag exempt?

cib · « **Reply #2 on:** October 11, 2019, 07:35:00 PM »

Thanks for the reply. I'm in the process of revamping the plans as I'm able to get a bigger barn due to changes. My mother in law was supposed to move onto our property and due to zoning that isn't allowed so now where her house would have been is where my barn/workshop will be.

Now I'm back to either a monitor barn or a saltbox. Trying to find some plans in the range of 24x30-32'.

Don P · « **Reply #3 on:** October 11, 2019, 07:55:10 PM »

One way, just modifying what you have there a little. Extend the center aisle up and put the upper monitor roof on those raised plates. Then run girts from bent to bent at the level of the upper end of the shed roofs, basically at the level of the current plate.

cib · « **Reply #4 on:** October 12, 2019, 10:08:34 PM »

Don,

Thanks for the replies. Would you happen to know a sawyer in the area that would deal with timbers? The ones I've found will cut anything I bring to them but few have anything in the size I'm looking for. It is really hard to find a 20'+ beam to be honest of any size.

nativewolf · « **Reply #5 on:** October 12, 2019, 10:53:38 PM »

@cib Send me a pm, I'm up north of you a bit but there are several guys that can do that for you in VA, one is a timber framer in Woodstock, his saw will do 40' if I remember correctly. There are also the guys that saw long bridge timbers. Lots of folks actually but send me a PM and we could chat and then narrow the list a bit so no one's time is wasted.

Don P · « **Reply #6 on:** October 13, 2019, 07:26:44 AM »

Good deal. Additionally it doesn't sound like this is ag exempt, what is the county requiring. Do you need sealed plans and grading?

cib · « **Reply #7 on:** October 13, 2019, 08:29:54 AM »

I'm in an A1 ag zone in montgomery county. I'm not certain exactly what qualifies as ag exempt in VA but in georgia the type of structure I'm building and zone is all I'd need.

Don P · « **Reply #8 on:** October 13, 2019, 08:07:44 PM »

Hmm, Montgomery county doesn't post an ag exemption affidavit form that I could find.
The ag exemption is a state law, building departments hate the exemption. Generally you need to know and understand the letter of the law going in. VA is a Dillon's rule state, a county cannot override state law. The exemption is for an active farming operation and the building must be on that farm for operations related to that farm. Silviculture is farming. Below is the gist of the law there is more in the big state lawbook "The Code of Virginia".

This is from my county's building dept website;
Farm buildings and structures may be exempt from the Virginia Uniform Statewide Building Code (USBC). In order to qualify for this exemption, the structure must be a specific purpose which is directly related to an operating farm. The Code of Virginia §36-97 and Section 102.3.6 of the 2012 edition of the USBC defines a farm building/structure as follows:

Farm Building or Structure: A building or structure not used for residential purposes, located on property where farming operations take place, and used primarily for any of the following uses or combination thereof:

1. Storage, handling, production, display, sampling or sale of agricultural, horticultural, floricultural or silvicultural products produced on the farm.

2. Sheltering, raising, handling, processing or sale of agricultural animals or agricultural animal products.

3. Business or office uses relating to the farm operations.

4. Use of farm machinery or equipment or maintenance or storage of vehicles, machinery or equipment on the farm.

5. Storage or use of supplies and materials used on the farm.

6. Implementation of best management practices associated with farm operations.

Exemption does not apply in a FEMA flood hazard zone.

If you don't qualify there ask what is required, chances are it will need a stamped set of plans, holler if you need that, I've got a couple of engineers up your way in mind.

cib · « **Reply #9 on:** October 14, 2019, 06:55:40 PM »

My call to the zoning department said they didnt see a reason a barn wouldn't be exempt.

Hope it goes well. My barn cant be taller than the house and that isnt an issue.

Don P · « **Reply #10 on:** October 14, 2019, 07:24:27 PM »

Cool. You can, if you want, design it yourself. As I was looking at it just now the same thing would work for making a gambrel, if you raise the center section of the main aisle it's really just where you connect the top of the shed rafters that creates a monitor or gambrel roofline.

Don P · « **Reply #11 on:** October 24, 2019, 09:41:08 PM »

Quote

Quote from: cib on Wed Oct 23 2019 22:20:22 GMT-0400 (Eastern Daylight Time)

Quote from: Sedgehammer on February 05, 2019, 12:00:58 PM
Searched the site and interwebs, hadn't had much luck in finding. If anyone has one or has a link, would be much appreciated.

Thanks
I didn't want to start a new thread but I was reading Sobon's book and he mentions the storage barn with a clear 20' span using 7x7 for the rafters, king post, and tie beam. They were strong enough to support a loft and storage. It appears they were 10' between bents according to the plans.
Are the sizes correct for that span? I've seen other plans recommend 8x10 for anything close to a 20' span with a king post trus.

Posted by: Don P
« on: Today at 08:40:39 PM »

cib, normally I'm the worlds worst about jumping off topic in a thread, but, I think repost this on the barn thread you started a week or so ago and lets put the evolution of your design there, I think it'll go to more than one Q&A round before you are done.

I need to reboot and do some dimensions and sketches for work right now, I'll check shortly, my gut says that is too light. I think that is one of Sobon's drawings of an existing historic structure, not necessarily a design that would pass nowadays without checking it out.
.................
Just bringing this over to the original thread.
I've looked at Sobon's drawing you pm'ed, he captioned it Frame of Miss Hall's School storage barn.

Here's how to check it;

A 20' span purlined kingpost truss roof, trusses on 10' centers.
The span of the top chord (rafter) of the truss is 10' and the tributary width is 10' bearing on that rafter (halfway to the next truss in each direction, 5' on each side of the rafter). So 10' rafter span x 10' trib width = 100 sf bearing on each top chord of the truss. 100sf x 40 lbs/sf total load= 4000 lbs bearing on the rafter.
Go here;
http://forestryforum.com/members/donp/beamclc06b.htm
Total load 4000
Dead load 1000
span 120
width 7
depth 7
#2 eastern hemlock Beams and stringers
click "show result"

Fail in bending strength, fail in deflection, pass in shear.

Go back up, click #1 Eastern Hemlock B&S and click "show result", pass on all three. That would be if the 7x7 top chord were unnotched for the purlins. Either putting the purlins on top of the truss or hanging them on the sides of the top chord say with inturned ear (concealed) joist hangers. I really don't like to use #1 design values. The TF Guild standards say to stick to #2 unless you have the timbers pro graded.

8x8 passes in #2 EHem.
8x10 passes in #2 Eastern White Pine.

Bottom chord and kingpost in tension are going to pass.

If one of those options is the way to proceed;
The next thing would be to check the heeljoint notch bearing for crushing at the angle of bearing of the top chord to tie, and the tie relish beyond that notch for shear.

cib · « **Reply #12 on:** October 25, 2019, 08:54:12 AM »

The 10 x 10 x 40lbs is the 40 lbs the snow load? I've read the dead load is 10lbs per sqft. The reason I ask is the snow here is 30 lbs.

Don P · « **Reply #13 on:** October 25, 2019, 09:54:08 PM »

Correct, 30 psf snow + 10 psf dead load for a total load of 40 psf

cib · « **Reply #14 on:** October 27, 2019, 06:48:56 PM »

Redoing the drawings.

I'm going to have just one full span beam all others will have supports. This will give me a storage section and the post wont interfer much there but open in the workshop area.

That should reduce the costs some.

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