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Small Cabin Forum / General Forum / concrete pier spacing
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barneycheeseman1
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# Posted: 1 Mar 2015 12:27
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Hi: I am building a shed my county code says I can build a 10x12 foot shed without a permit. I am using 3 2x6x12 pressure treated beams set on concrete precast piers. I would like to know the correct spacing for the piers under the 2x6x12 foot beams

AK Seabee
Member
# Posted: 1 Mar 2015 15:03 - Edited by: AK Seabee
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120 square feet must be a standard. I built the same shed for the same reasons.
On my shed I used the precast blocks on the perimeter with the all thread so I could adjust vertically if required. Ten years later it has not been required.
I placed 6 adjustable piers total. On the 12 ' run I placed them 6' apart, so three per side. I spanned the 10' with the 2x10 joists into a 2x10 rim board.
In between the pier blocks and 2x10's I used two 4x6x12 skids.
I heat the shed and store a couple 55 gallon barrels of water as well as heavy tools and equipment. Like I said, no noticable movement at all in the frozen north country. My soils are consistent with type 5 NFS gravel.
If yours are different you may have different results.

MtnDon
Member
# Posted: 1 Mar 2015 18:25
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Sheds without permits can vary in size from place to place. Here in NM it's 200 sq ft. I'm going to sound like a broken record... if you are building a shed to be an actual shed, store lawnmowers, dirt bikes and so on, then that is the shed the rule makers usually have in mind. However if you are building a shed to fly under the radar and turn it into a habitable building, even if only a part time residence, you should make certain that is going to meet the letter of the law. Here, and in many other locations, if there is intent to live in the shed, it is no longer a simple shed. It becomes a habitable building and subject to the same rules that apply to regular homes. Sometimes the shed rule is also premised on the shed being an accessory building, a building that is built after the main habitable building is built with permits and everything that goes along with that. Just mentioning because there are plenty of folks who have been forced to comply with the zoning and building regulations that are in effect.

barneycheeseman1
Member
# Posted: 1 Mar 2015 19:12
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Thanks for the input. The shed is only to be used for storage and not any living space and the size is !0'x12' (120 sq. ft.)
I am planning on using precast concrete piers with three 2x6 beams and 3 piers on each side and 3 piers on the middle beam. Question again is this to be the correct spacing or do I need more piers closer spaced?

Don_P
Member
# Posted: 1 Mar 2015 22:30
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You have to know how much weight the beams and footings are supporting, anything unusually heavy on the floor? Snow load in lbs per square foot?

A techno aside;
Depth builds strength in a beam faster and cheaper than width. The section modulus of a beam which in large part determines a beam's strength based on its' geometry is calculated using the equation bd^2/6, breadth times depth squared over six. Depth is squared, depth is building strength much faster than width. Your proposed triple 2x6 is rarely used for a reason, it has a section modulus of 22.69"^3, a double 2x8 is 26.28, a single 2x12 is 31.64... all else being equal a single 2x12 is a good bit stronger in bending than a triple 2x6. With a 10' joist span the joists should be 2x8's or deeper, a 2x6 joist plays out at around 8'.

barneycheeseman1
Member
# Posted: 2 Mar 2015 09:53
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Don_P I quess I am not explaining my use I am using One 2x6x12 on each side and one down the center of the foundation not grouping them together. under each 2x6x12 and setting 3 precast piers one at each end and on in the center of each 2x6x12

Don_P
Member
# Posted: 2 Mar 2015 19:06
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That is way too small a girder for anything at 6' span. To size the beams I need to know the loads.

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