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Storage & Organization

8x10 shed built without Treated Plywood for Subfloors

I am in the middle of a shed build and have the floors resting on PT 4x4 skids that sit on concrete deck piers. I originally was going to use PT 3/4" plywood but didn't see it with Tongue and Groove. So I purchased 23/32 in. 4 ft. x 8 ft. T&G Premium Subflooring. I've already built the floor and all of the frame is done and nailed to the floor. I still need to finish the roof and put siding up. I started reading about the importance of pressure treated flooring for sheds and now am worried I may have made a big mistake. I'm planning on using a prime/ sealant by Glidden to protect the top of the floor but not sure if that will help seeing how the bottom will not be protected. What should I do? Should I just continue on? The subfloor is 10" above the ground in the back and 12" off the ground in the front. 
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Posted 2015-08-24T05:37:50+0000  by Steamboat Steamboat
Hi Steamboat,

At this stage I would not ruin all that good work to change out the flooring. The biggest concerns are always rot and termites.

Since the floor is up on piers, rot is a not a major concern, To be safe I would treat the soil around the shed with termite stakes on an annual basis to prevent subterranean termite infestations.

If you have access to the underside of the flooring, treat it top and bottom with a product known as Tim-bor, this is a borate based insecticide, which controls rot and termites. It is mixed with water and sprayed on. I treated my attic with it 10 years ago after a small infestation and have had no further problems since.

You can treat all of the wood in the shed in addition to the floor, when the Tim-bor dries, the wood can be painted.

Once you've completed your treatment finish the shed and start using it.

Posted 2015-08-24T19:04:52+0000  by Mike_HD_OC
Hi Steamboat,

Copper sulfate is available in many forms and is the primary component, used today, to treat lumber against fungus.

Since you're already beyond installing a PT floor, the next best thing might be treating the undercarriage of you shed with copper ammonia complex.

In our Garden Department you'll find Liquid Copper Fungicide.

This concentrate makes up to 48-gallons and should be enough to last several years.

Mix according to the label and generously spray the undercarriage and ground under and around your shed.

This broad spectrum fungicide will protect your exposed lumber; then simply schedule re-treatment once a year at the beginning of your high humidity season.

Even though the process of injecting copper sulfate into the wood will protect longer, with regular surface treatments of this copper ammonia complex you'll get many years of utility out of your shed.

Although this product is not highly reactive, when spraying it is never a bad idea to wear protective gloves, use a respirator, and wear eye protection.
Posted 2015-08-25T15:43:58+0000  by Pat_HD_ATL
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