4x6 solid beam vs. 6x10 built up beam

[puglife122711]

Building a 16x32 house. Using 4 rows of 4x6 piers for the 16' and 9 piers down each row for the 32'. Debating on using 4x6 for the beams cause I can readily get them in 20' lengths and splice two together for the 32'. My question is would a built up beam of 3 2x10 be any more structural than a solid 4x6 beam? All splices would be over a post.

[Don_P]

a 4x6 has these section properties;
Area 19.25"
Section modulus 17.65"
Moment of inertia 48.52"

A 3 ply 2x10;
Area 41.625
Section modulus 64.17
Moment of inertia 296.8

Moment of inertia is usually the control, notice the difference.

Edit;
More, what I quickly wrote earlier describes the basic geometry of the shapes with respect to using them as a beam. In the next step of sizing a beam you look up the allowable strength values for the species and grade of wood you are using. Then those "base design values" are adjusted for various conditions. Bending strength is adjusted upwards 15% in the 3 ply built up beam because the defects are better scattered throughout the beam where in a solid sawn timber that knot compromises more of the beam.

[akwoodchuck]

Building a 16x32 house. Using 4 rows of 4x6 piers for the 16' and 9 piers down each row for the 32'. Debating on using 4x6 for the beams cause I can readily get them in 20' lengths and splice two together for the 32'. My question is would a built up beam of 3 2x10 be any more structural than a solid 4x6 beam? All splices would be over a post.

Am I reading this right? 36 piers for a 500 sq. ft. house? Holy posthole! My humble $.02 would be to go with far fewer posts, 10 or 12, and beef them up to 6x8s....gives you two rows of posts 8' on center, with maybe one more on each end to catch the skirting. About 3 sq. ft. of footing under each post, and a 3-ply 2x12 beam on top should be adequate...provided this isn't a four- story house   

[puglife122711]

If it were solely up to me I would be using 6x6 posts 3 rows of 7 posts and trippled 2x10 beams. But since the in-laws are helping with the build, I can't convince them that bigger beams mean less posts,and since they've built a house before I can't convince my wife, so my hands are tied. The final plan is a 20x36 5 rows of 4x6 posts and 4x6 beams.10 posts each row for a total of 50 posts. I gave in and since they are offering help and equipment I'm fine with it. I know its way more than I need, I've tried explaining all the span tables and charts,but all they have to say about it is"but for how long will it last like that." Building in Texas so no snow loads not in a floodplain. Will be a 1.5 story loft for sleeping. Planning on 10 foot 2x6 walls using a ribbon board at the 8ft mark for the loft floor joists. Still debating on getting trusses, looking into what my best options are for headroom in the loft.will have the kitchen and bathroom under the loft.

[Don_P]

TX... footing depth is only 12" below grade there. You could do a 20x36 full footing trench with a rototiller and a square shovel in a day. Pour that 8" thick with 2 strands of rebar 3" off the bottom. 3 rows of block would get you out of the splash on level ground. At that point the outside girders, piers, posts and those anchorage, alignment and digging headaches go away. The foundation is then braced. Doncha just love in-laws 

Try 8' walls and cantilevered attic trusses. Floor, kneewall and roof all in one lift.

[puglife122711]

I've uploaded some sketchup pictures of my foundation plans. posts are 4x6 and so are the beams. I have it drawn to use 3 12' beams to make up the 36' length. will the end to end joints work how I have it drawn out, if not is there a way to make it work like that or should I go ahead and order the 20' lengths and lap joint them in.







there will be 5 rows of ten piers each for a total of 50 piers

[MountainDon]

 I see all those pieces; all those piers, all those braces, and plate connections and want to run out and rent a roto tiller and dig a trench for a 12 inch deep concrete footing. Or a PWF using packed crushed stone instead of concrete. I could not do that many piers along with all the other pieces. Seems that might even cost more (materials and labor)  than the other foundation solutions.

[puglife122711]

Yes it is going to be alot of work but I'm still young and have enough energy for it.and will have the help of in-laws and augers. Price for everything for the foundation came out to right about $1,500. And I consider my labor free cause I'd rather do it than pay someone else to

[garyc]

I did my barn foundation with concrete, 22'X36' with a footing 24'' wide and 24'' deep with a 8''x18''wall less than $2500. After you do your post and beam system you still need to add a skirting around your building. Witch will add cost to your foundation and more labor. Don_P and MountainDon has been there and done that. I'm glade that we have people like this that is willing to take there time to help us out. Sometimes Trying to save a little money can cost you a lot Moore in labor and headache. A simple footing with a block wall would be easy to do. YouTube can show you how to lay block it's easy to do.       

[puglife122711]

heres some screenshots of the loft design, will this be enough support? it will be a 12x20 loft. with a bedroom and area for desk and computer. floor joists are 2x8 16" on center. posts are 6x6 two in the open area and two in the walls. on top of posts triple 2x12 beam spanning 12 foot. is the beam even big enough for the span? beams are 5 1/2 foot apart making floor joist span about 6 1/2 foot at the most. have the joists sitting on the 2x6 ribbon board and using joist hangers for where they attach to the beams.

[Arky217]

The following link may help.
Arky

http://countryplans.com/smf/index.php?topic=14023.msg182880#msg182880