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22x32 post and beam house

Started by dewaynearnold, December 30, 2018, 05:45:49 PM

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dewaynearnold

I have been reading up on post and beam and timber framing for quite a while but I am at the point where the asking questions come in.. I am looking to build a house 24x32 (not set in stone, it will depend on the spans I can run.. ) the timberframe part of the house will be what I need help with.. I will pour concrete piers 12"x12" or 10"x10" anywhere from 3ft-4ft deep depending on if I hit solid rock.. it will have about a 2ft crawl space at least under it with the posts mounting directly to the concrete piers. I plan on using 8x8 vertical posts out of oak.. i want 12ft ceilings so about 13ft long on the exterior walls, I would like to make a small loft up stairs, so the roof would be a 10/12 or a 12/12. The horizontal beams I had planned on using was pine, old growth pine.. what is a safe span for Pine in a 6x12 or 8x12? I want to overbuild it but i dont want to make it harder on myself than I need to.  I also am not decided on the spacing on the beams on the exterior walls.. 8ft or 10ft or the type of truss I will be using.  I  looked at the beam calculator and can size normal 2x dimensional easily.. but the large beams are throwing me off.. I can do a rough drawing if needed.. I am sure my description is really unclear but i am the type that can visualize but can not explain easily without drawing it out. my zipcode is 72662, we get very little snow here.
Dream is to build a timber frame/ post frame house in the design process now..

Don P

Welcome to the forum :)
First off, start with a good foundation, from the foundation chapter in the codebook;

QuoteAll exterior walls shall be supported on continuous solid or fully grouted masonry or concrete footings, wood foundations, or other approved structural systems that shall be of sufficient design to accommodate all loads according to Section R301 and to transmit the resulting loads to the soil within the limitations as determined from the character of the soil. Footings shall be supported on undisturbed natural soils or engineered fill.

Basically the requirement is that exterior walls be braced and they are over braced foundation walls. Whether you are in a code enforcement area or not, the physics doesn't change, piers aren't a good idea at all.

Looks like the snow load is lower than the minimum design wind load of 20 psf, so that would be your design roof live load.

What species of pine, I'm assuming one of the major southern yellow pines? Size and span depend on species, grade and load, so we don't have enough info yet. It's a little bit of a circular process, so yes, start with a sketch and a healthy dose of patience and we can show you how to size a simple beam.

dewaynearnold

Piers may of been the wrong word, and I should of explained my plan better. I planned on doing the foundation in 2 steps.. the bigger "piers" where the timbers will sit, I will pour those deeper and thicker than the rest of the foundation 10" square or 1ft square. then either pouring between the piers with 8" concrete or use block on a footing.  The freeze line here is about 18" so i planned on making them a minimum of 2ft all the way around the spacing between the piers. My goal is to be about a foot exposed all the around on the lowest side. I am going to upload some pictures in the next post from my phone to give a rough idea, the side view is just an idea, nothing is set.. and of the pine I have so maybe someone can identify it   The reason I wanted a 12ft exterior wall is I want to create a "lean to" off the side to put the bedrooms and bathrooms and a porch on the other side,I want to design it now so I can add on to it later so I want some flexibility.  the pine measurement is at 22ft its about 29" at base

I forgot to add that I want to do mortise and tenon with wood pegs, I may occasionally use the long GRK lags. As to mounting the timbers to the concrete i was going to either fab my own steel brackets or use the timberlinx a475 system

Dream is to build a timber frame/ post frame house in the design process now..

dewaynearnold

Dream is to build a timber frame/ post frame house in the design process now..

John_P

Welcome to the forum, it is up to you but it may be easier to simply buy plans that have everything you need as far as the timber frame goes.  Timber list, cut sheets ect  Timberframehq has some, other members including Jim Rogers may be able to help with plans as well.  Good luck

Ljohnsaw

That tree "looks" like Ponderosa but I don't think they grow over your way.  Your rough plan looks a lot like mine!  I am also putting in a ridge beam and common rafters.


 
I drew the plans and had Fire Tower sign off on the plans.  Ben is a registered PE in California though he works in Rhode Island.
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Ford 545D FEL, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 42" capacity/36" cut Bandmill up to 54' long - using it all to build a timber frame cabin.

dewaynearnold

How big is the one you are building? I want the posts spaced with structural integrity but also not be in the way.. I plan on using Ridge beams as well.. 
Dream is to build a timber frame/ post frame house in the design process now..

Don P

Do the foundation in one step, pour a continuous strip footing around the entire exterior with 2 strands of rebar 3" off the bottom of the trench, then block or pour an 8" thick wall around the entire perimeter. What you are planning is going to suffer from differential settlement as each pier and wall section finds its own level. With the full perimeter foundation the floor joists and exterior walls are bearing on the foundation wall rather than on a girder out there, a better floor. Getting off to a good start. In the long run it will be cheaper and better.

Looks like nice SYP timber. It looks like the bottom should yield #1 material, actually that looks like #1 dense (be conservative though), the next log probably #2, maybe post material in the uppers and beams from the butts. You can read up on grading on the SPIB and NeLma websites.

I like ljohnsaw's ridgebeam. One of the problems in a high posted cape without a ridgebeam is the rafter thrust pushing hard on that raised kneewall and the tie connections. Hanging the rafters from the ridge eliminates that. Running with that idea on your size I played around a little with that idea;





Now for sizing a beam. The area in red is showing the tributary area loading one of the tie beams under the floor joists. That tie is spanning about 11' and is carrying the joists from halfway to the tie on either side, left to right in the pic, so about 8' wide... 8' x 11' of trib area, 88 square feet. The design floor live load is 40 pounds per square foot plus 10 psf dead load (the weight of the materials themselves)= 50 psf x 88sf=4400 lbs total sitting on the red area. Dead load= 88sf x10psf=880 lbs.

Using this calc;
http://forestryforum.com/members/donp/beamclc06b.htm
Enter;
4400 lbs total load
880 lbs dead load
132" span
8" width
8" depth
#1 Southern Pine >5x5
Click "Show Result"

Notice allowable Fb 1350 psi, E 1.5, Fv 165 psi
Notice Max bending moment 6050 foot -lbs, section modulus required 54"3 , you have 85"3 Bending passes

Deflection passes with about 3/16" sag at full load. Shear is good.

Now go back up and click on #2 Southern pine and click show result again.
Notice allowable fiberstress in bending drops to 850, huge bending strength hit, stiffness drops to 1.2 and you slightly fail in bending, grading is critical... don't mess around or bump those ties up to 8x10's if it looks more like you have #2 material. Deflection is still ok at a little over 1/4" sag at full load. Bending is the structural concern, sag is not safety it is serviceability, bounciness.

That assumed you build it as drawn there, joists sitting on top of ties. I like to build that way rather than notching the ties and dropping the joists in, which destroys a lot of bending strength that you'll have to replace. If you want to go that route we need to talk more. Anyway, that was beam lesson 1. Run a joist, I haven't yet, play around and see what you get, holler if you get stuck, then start working your way around the structure, check the plates and ridge. I made everything big 8x8 in the sketch although the ridge is really 12" tall at the point I'd still KISS and call it an 8x8 for now. Joists are drawn as 6x8's at 32" on center... so trib area on them is 2.66'x8'x50psf. Then start checking the columns with the column calc, running from tie up to ridge those tall ones are 13'8" in my sketch. All that is just an exercise, you'll probably want to modify the plan, that was just an idea that popped to mind after seeing John's pic.

Ljohnsaw

Quote from: dewaynearnold on December 31, 2018, 08:12:07 PM
How big is the one you are building? I want the posts spaced with structural integrity but also not be in the way.. I plan on using Ridge beams as well..
My foundation is made from 24" long Faswal blocks.  To make the corners, you need to have an odd lengths.  So my overall is 25x49 on the outside, 23x47 inside.  The space between the posts is 12' (+/-) in each direction except the last bay (bedrooms) where they are 12x11 or so.  I have 350+ lb/sq-ft snow load (ground) so I've gone steep pitch (53°) metal roof.  My corner posts are 8x8, all others 8x10.  My center posts have something around 10,000 pounds of load, IIRC.  And just because I can, I made the end lower posts in the center 8x12.  I wanted the mass look.

I have a long thread on my build and another long one on my design process that was shaped by all the great comments and suggestions from the FF.
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Ford 545D FEL, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 42" capacity/36" cut Bandmill up to 54' long - using it all to build a timber frame cabin.

dewaynearnold

Would a slab be a better option in my build?
Dream is to build a timber frame/ post frame house in the design process now..

Don P

There is nothing "wrong" with a slab, I do like to get the wood up out of the ground a good bit. Nor is there anything wrong with a full crawlspace or basement. In a crawlspace I try hard to get a "rat slab", a 2-3" thick pour to provide a good vapor seal and to make it better on the guys working under there, and in out case to keep the groundhog on his side of the dirt. By the time you do a slab correctly it has a continuous perimeter footing as well. There is simply a lot wrong with piers, they have a long and rich history of failure. In the codebook nowadays they are required to be engineered, and for good reason, whether it is going to be inspected or not. My house has a raised slab under half of it and a rat slabbed crawlspace under the other half, where all the plumbing runs.

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