# Do i need pressure treated floor joist?



## Lupus71 (Sep 16, 2012)

IM building a 16x24 shed/shop and need alittle help. I have my footings dug and will lay block 16" above ground, I'm hoping this is high enough to be able to use untreated wood for the floor joists and band what do you guys think? I did some framing years ago and don't recall treated lumber under any houses so why would a shed need it? Also I checked and my home doesnt have treated either so????


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## joecaption (Nov 30, 2011)

Any less then 18" is suppost to be pressure treated.
But for a shed I'd just lay 6 mil. plastic on the ground and stake it down with 16" insulation hangers as a vaper barrier.
I'd also make sure there was foundation vents.


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## ddawg16 (Aug 15, 2011)

What Joe said ^^^...

In addition....anything that touches concrete needs to be PT.

It also helps to put your location in your profile. If your in CA....then I think you would be fine....execept I would suggest installing a metal strip (sticking out about 1") between the footing and PT sill....it keeps the termites from crawling up...and with proper ventilation, no vapor barrier...but it you don't live in CA....vapor barrier....

One last item for thought....if you think you have any plans to crawl under there.....you want those 18". Trust me....you will understand after spending some time under there......trust me...I know.....the hard way....


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## SeniorSitizen (Sep 10, 2012)

If you are interested in breeding termites put the plastic down*, *they'll love it *.*


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## ddawg16 (Aug 15, 2011)

Fairview said:


> If you are interested in breeding termites put the plastic down*, *they'll love it *.*


I would love to hear the science behind that.


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## GBrackins (Apr 26, 2012)

joecaption said:


> Any less then 18" is suppost to be pressure treated.
> But for a shed I'd just lay 6 mil. plastic on the ground and stake it down with 16" insulation hangers as a vaper barrier.
> I'd also make sure there was foundation vents.


as Joe said ^ here is the code section http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_3_sec017.htm

to check out termite infestation probability map see Figure 301.2(6) on this link http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_3_sec001.htm

for protection against subterranean termites check out this link http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_3_sec018.htm including section 318.3 and plastic sheeting

good luck! :thumbsup:


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## joecaption (Nov 30, 2011)

Want to prevent termites then get a pretreat before the floor goes in. Far cheaper to do a pretreat then a treatment later.
They can just shoot the chemical inside the blocks and flood the footings before they get back filled, no drilling needed.


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## hand drive (Apr 21, 2012)

If the foundation block is 16" from the earth, a 2x6 or 2x8 treated sill plate will be 1 1/2" thick so that is close to 18" to the underside of the joists.


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## Duckweather (Mar 26, 2012)

I haven't looked for it in a while but there were some wood preservatives for use on untreated lumber not in contact with the ground. Cuprinol used to make one. You just spray it on with a garden sprayer. (Or Creosote, if you don't mind toxic waste)


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## joecaption (Nov 30, 2011)

Timbor or Boracare may be what your thinking of.


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## Large Orange (Mar 7, 2013)

I built a 12 x 24 shed 27 years ago with untreated 2 x 6 joists sitting on treated 4 x 4 runners sitting on solid 4" blocks sitting directly on the ground. I did have to use (2) 4" blocks on the low side. So my joists are appx 8" off the ground on 1 side and appx 12" off the ground on the other. I did use PT rim joists as they are not completely covered with siding. Every part of the shed seems as sturdy as it did 27 years ago. I didn't know better at the time or I would have used PT joists that close to the ground but it has held up well. I do have open air space, not a enclosed block foundation.


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## hand drive (Apr 21, 2012)

Large Orange said:


> I built a 12 x 24 shed 27 years ago with untreated 2 x 6 joists sitting on treated 4 x 4 runners sitting on solid 4" blocks sitting directly on the ground. I did have to use (2) 4" blocks on the low side. So my joists are appx 8" off the ground on 1 side and appx 12" off the ground on the other. I did use PT rim joists as they are not completely covered with siding. Every part of the shed seems as sturdy as it did 27 years ago. I didn't know better at the time or I would have used PT joists that close to the ground but it has held up well. I do have open air space, not a enclosed block foundation.



location determines the building procedure usually somewhat. your shed has held up well for sure for being that close to dirt with the floor system...


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## md2lgyk (Jan 6, 2009)

ddawg16 said:


> One last item for thought....if you think you have any plans to crawl under there.....you want those 18". Trust me....you will understand after spending some time under there......trust me...I know.....the hard way....


Amen to that. When we designed our log home, we did not want a basement. We specified a 48-inch crawlspace so we could make some use of the space. The well pressure tank, most of the HVAC ductwork, and the backup gas furnace are all down there, along with lights and some receptacles. I have to go in a few times a year to service the electronic air cleaner, and it's really easy.


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