Sizing Chart for Timbers

[tadkins]

I am building a covered patio off of the back of a new addition on my house.  I am building the patio from SYP from my property, have a portable sawmill coming to mill it out.  My question comes from building inspector on beam span.  My patio is 16'x16',  4/12 pitch, 4x8 rafters 32"OC, 12" Overhang, 8x8 posts, 4x12 side girders.   One end will be tied into addition and the other end I want open.  I planned to use 4x12 Ridge Beam, but inspector is not sure on span rating and wants to go with triple 2x12 or 2xLVL.  My span is 16' and fireplace framing will be offering some support on house end so actual distance will only be 14'.  Next issue, plan was to put 4x12 cross support on open gable end level with side girders and vertical support beam from cross beam to ridge beam without a vertical center post to ground for support.  I want to leave it open on the end, but don't want to mess up my curb appeal by mixing in LVL.  Inspector wants load chart to show 4x12x16 will hold the weight without ground support.  They also want to use 2x6 T&G instead of 1x6 T&G for ceiling.  I plan on stripping it also with either 2x4 or 1x4 to add extra for metal screws to hold.  Anything that is not cookie cutter they don't understand.  Any help is appreciated.  Also I live in Virginia if that helps with load calculation.

[beenthere]

Welcome to the Forestry Forum

Frustrating when working with an inspector who is just guessing at sizing of load bearing beams.

Hang tight, as there are some members who are involved and will study the problem.

Do you have a drawing of the addition?

[tadkins]

Thanks for the help!  I've tried uploading the pdf of the drawings.  This whole house has been a project for the last couple of years and have been able to avoid the inspector's office until now.  He hasn't been bad yet, I just think they should have charts on hand to verify the info, not me having to prove it.  This drawing was earlier in the process and it shows 4x10's instead of 4x12's and 6x6 instead of 8x8. 

[tadkins]

Its not shown but will have 8' collar ties on every other rafter on patio, if it makes a difference.

[Jim_Rogers]

To begin we'd need to know the snow load for your area.

I'm sure if you do an internet search you can find "span tables" that should be able to show you the spans that timbers can span.

I don't personally have a site where you can get them.

Jim Rogers

[tadkins]

Snow load is 25 lbs sq ft.  Wind 90 mph if this helps.  I just got message plan has been approved but would still like to use 4x12 ridge beam if possible.  Thanks for the help.

[tadkins]

Update: Picked up plans today and still requiring either post under gable end or transfer load to the beam (with documentation required).  Also same on the ridge beam, needing documentation to use 4x12.  At least I can get started on the foundation now though. Thanks for any help.

[Thehardway]

Tadkins,



First off, welcome to the forum.

It is a difficult call here.  I can understand the building inspectors viewpoint.  What you are doing does not exactly fall within the scope of Timberframing or Prescriptive dimensional lumber framing.  The Inspector feels that he is already giving up a degree of his safety margin by permitting you to use non-grade stamp, non-kiln dried lumber. He is unlikely to give any more on his margins.

From a Timberframing perspective it would be built of larger timbers and there would likely be a detailed joinery drawing and braces.  By your drawings, your gable end is actually functioning as a truss to support the ridge beam from which your rafters will hang.  Unfortunately for you, in a truss, connections are critical and we have no detail of your connection plans.  My recommendation is that if you want the look of a kingpost truss and don't wish to use LVL's, have a true kingpost truss built with appropriate posts and braces.  It will look better and if you upped the size of your ridge beam to 4X14 I doubt the inspector would have an issue with the assembly.  Adding depth to a beam does a lot more than adding width or doubling up.

We could better help you with a true kingpost truss as there is historical data and in use structures to draw from in determining appropriate spans.

BTW, You have a nice looking home and the porch with that stone fireplace will be too nice an addition not to have an authentic TF truss.  Where are you located in VA?   I am near Lynchburg/Danville area

[tadkins]

Thanks for the reply.  I am open  to suggestions or designs for support.  I  can get 1/4 steel plating and lag bolts for the connections and changing to a 4x14 ridge beam shouldn't be an issue.  I will probably have to have some type connection for the rafters as well other than toe nailing.  I am sawing the lumber out of my own pine timbers and they are not sawn up yet.  I have the logs down just not milled out yet.  I am on a budget and trying to avoid paying for engineering. 

From the pictures I saw I couldn't tell how I would build it to support a ridge beam.  Looking back I might should have submitted it with all trusses and left out the ridge beam.  The inspector's office has really not been that hard to work with, just any bumps make it difficult and this is out of my league to provide documentation myself.  That's why I've come for some expert advice. 

Thanks for the compliments on the house.  Its been a total remodel and the addition will be it for a while I hope.  Can't wait to get some rock across the front also. We bought a farm from an estate that had sat vacant for several years and has taken a while to clean up.   I am not to far from you Thehardway.  We are just south of Roanoke about 20 miles.

[beenthere]

I can only suggest you bite the "engineering" bullet and get some help there.
The inspector will be a bit nervous putting his/her signature on something that is a "let's hope this works ok" design.
Seems just an engineer working up the design values for your beam to compare to the design values suggested by the inspector should be enough, but that is for the engineer to address.
Wish you well. You will fare better keeping the inspector happy (and hope that halfway through, there isn't a new inspector that you have to appease).

[Thehardway]

tadkins,

Hey, we are almost neighbors ;D

Hopefully I don't get in trouble with the admins here but I think this would solve all your problems.

It is plans for a 16X16 kingpost timberframe structure.  Cost is $47.00  hard to beat that and it should get you past review with your inspector.  I have no affiliation with these folks, it just popped up in a Google search and looks like it fits the bill for your job.

http://timberframehq.com/timberframehouseplansandkits/16x16-timber-frame-plan/

It includes cut list etc.  You should be able to work from these.  Fairly straightforward.  Nothing real complex.

There are other more local TF companies that probably have 16' Kingpost trusses on file with spec that they could sell you to build from.  That avoids having to replicate already previously done engineering calcs and saves you time and money if you are willing to do the milling and joinery work per their plans.

Does this help?