24x32 in East Tn

[phasefive]

We began our cabin build last week...I hand dug down 8-12" and hit solid rock. Poured 4k pounds of hand mixed concrete... piers and footers. Average footer was 18"x18"x8"...rocky soil. I used 12" sonotube piers due to availability at HD...18 piers total...majority are between 16"-18" high....the rear row in approx 24" high all the way across.

The piers are 8' OC around the perimeter the 4 middle are 10' span. I plan on using 4x10 beams on top of the 4 rows of piers (simpson tie connected)  and 2x10 floor joists. In hindsight I'm concerned that I need more piers or at least cross-brace the 24" high rear piers...thoughts?
https://plus.google.com/photos/116811313147906140326/albums/5814981465150037169?authkey=CIiY17Tb9LjFGg

[MountainDon]

24x32.... single story?   loft?   1 1/2 story?   

[UK4X4]

Were the piers tied into the rock ?

Ie drilled and resined rebar or expanding bolts and all thread

[phasefive]

I'm thinking a single story...w/ a small loft. I did not tie into the rock.

[MountainDon]

Brief comment before I run off for the morning....

Is assuming the roof will be a gable type with the peak running in the 32 foot direction correct? Is it also correct to assume your roof will be built with rafters? Or would you want to use factory built roof trusses?

Before going any further along with anything you should know exactly what it is you are building, For example the foundation for a single story will be different from that required for a two story.  Will there be load bearing walls on the interior, or will the interior walls just be partition walls?  In general it is desired to design from the top down. It's the only way to get structural elements sized correctly.

Just off the top of my head the 8 foot spacing seems too much for 4x10 beams; or the beams too small for 8 foot spacing, however you want to look at it.

[phasefive]

thats correct looking at a gable roof running the length of 32'...I'll likely build truss' onsite. No load bearing interior walls. I can beef up the beams to 6x10 or 8x10 if necessary...due to the remote nature of the property this would be easier than pouring more piers. What do you think? Thanks for all the help.

[NavyDave]

What part of East TN are you in? I'm on the plateau North Of Crossville building a Victoria Cottage.

I built on top of bedrock also, ran into it around 20 inches down and I drilled with a rock drill and mortared rebar prior to pouring my piers (sounds harder than it is). Pouring additional piers may seem harder but might be worth it in the long run to be able to pin them to the rock.

I look forward to following your project 

[phasefive]

I'm in Vonore....in the cherokee NF. I agree...I think I'll pour some additional piers.

[MountainDon]

Using the girder table in the IRC (section R502.5 Allowable girder spans.) here's some info to consider...

IF there was no loft, just a single story we'd use the "roof & ceiling" section of the table. There is no section for lofts, so we should be conservative and go to the section "roof , ceiling and one clear span floor" (the loft). The table has values for 20, 28 and 36 ft wide buildings. It is ok to interpolate values. We'd use the 30 psf ground snow columns.

4 - 2x10 should work out for 8 foot spans. Have a look at the table; see what you make of it.

I'm not sure what to think of the 10 foot spacing on the interior area. That will not be supporting roof loads so



You mention building your own trusses for the roof. That is not a simple, nor typical DIY project. Rafters would likely be easier if there is no chance of having factory trusses delivered to the site. Just wondering if you have plans/drawings for that or what? There are "attic" trusses made that allow a room or open space up there. But typical trusses have a web system that eats up the space and makes it usuable mostly for simple storage of boxes, etc.

[phasefive]

I purchased the 1.5 story 20x30 plan today on this site. I looked at the link thank you...I agree with you...it looks like I can get away with 4 ) 2x10's. Thanks for the help.

[MountainDon]

I purchased the 1.5 story 20x30 plan today on this site

With a 24 foot wide project the info from a 20 ft wide plan will not be truly useful... Stretching wider is not as simple as making longer with the same width.