Timber Frame Outdoor Kitchen

[cmiller]

I am building and outdoor kitchen and was wondering if anyone could help me with sizing for my beams. I'm not sure is my terminology is correct so bear with me please. All beam material will be Douglas Fir. Here are the sizes I have proposed:

Building:
Size: 18' x 20'
Roof Pitch: 12/12
Post Height: 10'


Posts- 8x8
Braces gable- 3x8x51
Side Braces= 3x8x36
Side top plate: 8x8x25'3"
Gable bottom cord: 8x12x18 (outside)
Ridge Beam: 8x8x25'3
Rafters: 3x8x16'
King post: 8x8x6' 8-1/2"

The ceiling will be tongue and groove car siding, pine and the roof is metal
Any comments or help would be appreciated
Thanks

[Don P]

Hi-C, welcome to the forum 
Missing one piece of information for checking gravity load, what is your design snow load, or where are you?

At first blush I see a detail I don't like, those projecting beam ends are a recipe for inviting water into the joint and beam. Either figure out how to cap them well or tuck them under, behind a fascia if possible.

[cmiller]

I live in Wichita Kansas. I can tuck them under, I was thinking of 2' overhangs on the gables and going to 1' on the sides, design wise is that a good idea?

[Don P]

Witchita is in the 15 psf snow load belt, wind would control, the prescriptive minimum is 20 psf.

I'll sit on my hands and be ready to help 

[fishfighter]

One thing I would do different is not go with 10' post, but drop them down to 8'. Reason. Lower will block more sun, rain and in your case snow.

[Don P]

To start at step one, it would be good to describe the load path. This is checking vertical gravity load only.
The ridge supports half the weight of the roof, it is supporting the upper half of the rafters on each side of it.The eave wall plates support the lower half of the rafter load, 1/4 of roof load on the eaves wall plates on each side of the building.
The ridge is supported by a post at each end that lands at midspan on a beam spanning around 17.5' (allowing for some bearing length at each end).

The ridge is supporting 9' x 10' x 35psf (20LL+15DL)=3150lbs
https://forestryforum.com/members/donp/beamclc06b.htm
I get a pass

The wall plates are supporting less area with the same timber, pass

Check the midspan point load on the center bent it is supporting the most roof area 90sf again so 3150 lbs delivered down that post to the center of the tie beam.
https://forestryforum.com/members/donp/beamclc_ctrpointload.htm
I get so close it is the difference in how I look at spans, I'd call it a tight pass, use good material, I'm using #2.

Rafters are supporting quite an overhang, try it as a beam overhanging a post 9' on the inboard span, 3' on the overhang, they look to be on 3' centers. Load per foot on the beam(rafter) is 3'x 35psf=105 lbs per foot load all along the rafter.

At 3x8 use the dimensional lumber design values, with all adjustment factors figured in; Fb 1920psi, E 1.7, Shear 288 That is a huge jump from the heavy timber design values of Fb 825, E 1, Fv 165
https://forestryforum.com/members/donp/oerhangbm.htm
Pass.

No really please do some y'all, that was 3 designs in 2 days. I've had my practice turn.

[mudfarmer]

No really please do some y'all, that was 3 designs in 2 days. I've had my practice turn.

Hi Don,
Really appreciate all the free consulting you have given out on this forum over the years and also the calculators and tutorials.
I just started running through this as an exercise to learn from, with same design values except snowload for my area which is listed as 70PSF and kept the 20PSF live wind load because I don't know what to use there right now. Section Modulus FAIL on designed 8x8 Doug Fir ridge beam. I don't have Doug Fir so ran it with EWP, Still a FAIL on Section Modulus, had to increase to 12"x16" #2 EWP or 10"x14" #1 EWP to get a PASS :D
15PSF? Boy that sounds nice


Am doing something wrong or not understanding how to crunch the #s for midspan point load on center bent... Will have to keep playing with that. Not sure I fully understand the output and the help page is for uniformly loaded not point loaded. Time to read and learn more!! 8)

[mudfarmer]

No really please do some y'all, that was 3 designs in 2 days. I've had my practice turn.

Hi Don,
Really appreciate all the free consulting you have given out on this forum over the years and also the calculators and tutorials.
I just started running through this as an exercise to learn from, with same design values except snowload for my area which is listed as 70PSF and kept the 20PSF live wind load because I don't know what to use there right now. Section Modulus FAIL on designed 8x8 Doug Fir ridge beam. I don't have Doug Fir so ran it with EWP, Still a FAIL on Section Modulus, had to increase to 12"x16" #2 EWP or 10"x14" #1 EWP to get a PASS :D
15PSF? Boy that sounds nice


Am doing something wrong or not understanding how to crunch the #s for midspan point load on center bent... Will have to keep playing with that. Not sure I fully understand the output and the help page is for uniformly loaded not point loaded. Time to read and learn more!! 8)

This recent post https://forestryforum.com/board/index.php?topic=111330.msg1743031#msg1743031 from Don P helping another member on July 9 was very helpful!!

[Don P]

Thanks for the kind words, although, looks like he hasn't been back to see all that fine pontificatin'  :D.

On combining max wind and max snow loads. I was doing that on something in front of a local engineer and he asked my why. He pointed out that if the wind is blowing at 90 mph it is unlikely that design snow load will be on the roof. So one or the other, whichever produces maximum load, or maximum load in the direction you are checking.

Absolutely on checking different scenarios, I've learned a lot playing with other people's designs.