12x18 Workshop in NY

Started by rugger8, January 10, 2013, 03:19:51 PM

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rugger8

MtnDon,

Thanks, but unfortunately, I am still a little lost when reading those span tables. ???  But in general it appears I need to do more than 3 piers for an 18 ft. length.  If I do 3, then each beam would span 9' between piers, probably too much.  If I add a 4th pier, the spacing drops to 6' and if I do 5 piers, then the gap drops to 4.5'.  So, when I think about it that way, definitely need to do at least 4 and since I am on a slope, would probably be better off just doing 5 piers per beam. 

Thanks,

Jeff

John Raabe

Adding more piers also reduces the load on the soil for each pier and makes any given beam stiffer.
None of us are as smart as all of us.


MountainDon

Just because something has been done and has not failed, doesn't mean it is good design.

MountainDon

This should be better than the first hurried note...

Re TABLE R502.5(1) GIRDER SPANS
The building width numbers *20, 28, 36, can be extrapolated. That is in the footnotes.

The left hand column describes the building. "Roof, ceiling and one clear span floor" best describes your building I believe

We'll look at the 20 ft wide column under the 50 PSF snow load. Scroll down and see where the 20 ft column reads "7-5", 7 feet 5 inches. On the left that aligns with  "3-2 × 10".  In the 28 ft wide column the span is listed as "6-5".    , a difference of 12 inches.

28-20 = 8 ft.....     20 – 8 = 12 ft.   your building width.
So you can take that to mean that you could use "3-2 × 10" for a beam with the supports  "7-5"  plus 12 inches,  apart. Or = 8 feet 5 inches ,  but IMO that would be pushing the gueeswork,   

We could calculate actual loads and run that through a beam calculator.

Other combinations could be tried too.
3- 2x8's would work at 6 feet spacing; 6x6 piers. Nial the triple 2x8's together in situ on the pier tops. Use some ½" material to space on both sides to fit whatever brackets/ties are used to tie the beam to the pier.



I don't like slopes which was why we graded our slope to level. 

Piers offer no lateral support in some soils and under some conditions, like waterlogged soil.

If you did 5 piers with brace/shear wall sections at the corners, between piers, with ¾ PT plywood nailed over pier and beam faces, that would be bracing that would be hard to beat. Of course this is only a shed, not a residence, so maybe that is unnecessary.

The figures do not make allowances for extra heavy interior loads such as lathes and milling machines.


...now I'll be MIA while fixing (I hope) a broken computer.

Just because something has been done and has not failed, doesn't mean it is good design.