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Question DetailsAsked on 11/6/2017

who can jack a shed in order to replace the subfloor framing

My dad put a vinyl shed up 5 years ago. The vinyl flooring inside is fine, but the perimeter of the wood decking platform that the shed lies on is starting to break apart. This outer perimeter is exposed to debris and all sorts of weather conditions. I stain it every spring, but perhaps this plywood was not treated. The shed is not leaning, and the flooring inside seems sturdy, but if the outside perimeter damage continues to get worse and creeps in towards the center of the shed, I am worried that the inside flooring will have no support and collapse from the weight of the shed and the things in it. I believe the shed may have to be jacked up in order to replace the plywood subfloor framing.

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Depending on how big and heavy it is, couple of choices - though of course the more moving and jacking up you do the greater the chance the connections will pop free or break - and of course don't get rough with it if temp is below about 45-50 as they get real britttle at cold temps. If winter has hit in your area I would wait till spring -they are real intolerant of moving around in cold weather.

Jacking it straight up is not likely to be very workable because with a reasonable jacking height (car jack or bumper jack works fine for normal sized sheds) you still won't be able to remove the existing decking and put on new easily - especially since it sounds like you may just be running a circular saw around the edges to remove a strip of plywood to replace, not needing to remove the entire plywood deck. (Obviously empty it out first before jacking/moving it).

I would get a few scraps of wood (even firewood logs) to support the overhanging edge, and disconnect it from the deck if screwed/nailed down, then slide it a foot or two toward one corner to expose two sides of the decking at a time - propping the shed up on the blocking so it does not sag and crack.

Or you could slip a few 2x's in under it as skids or skis after jacking it up one end at a time, running all the way across, then slide it and them around a couple of feet, using the overhanging 2x's to support the shed. When doing this, easiest if you nail on a 2x scrap block on top of the overhanging slid ends (with the end of the 2x sticking out a foot or so, so the added block acts as a stop to keep the shed from sliding off the 2x - so when you push the shed to move it the 2x's stay under the shed by themselves). So the 2x's would need to be a couple of feet longer than the shed is wide so they stick out both sides.

If the plywood is pretty much shot then put some 2x blocks on one side of the deck framing to support nailed-on skid pieces (with the top of the skids at deck level) and support the other end of the skids (and maybe middle) with scrap blocking or cinder blocks or such (sort like porch framing of the side of the deck framing), and just slide the shed totally off onto the skids which would be sort of cantilevered off the side of the deck framing. That would free up the entire plywood surface at one time for total removal/replacement - then when done slide the shed back onto the new decking.

Course, if not heavy (say one of the 6x8 or smaller plastic box store sheds like by Rubbermaid) a couple of people can probably just lift or skid it off the platform on a few 2x's supported and tack nailed on a couple of scrap ledger boards nailed to the deck framing, below the decking.

To get this done commercially, a Handyman with a helper (or you if physically available and able) should be able to do it, as could a Carpenter - Framing or most Deck and Porch companies. Or maybe one of those shed-building companies. Of course a General Contractor or Builder- Garages and Sheds could also do it, but pretty much overkill for this type job and they are likely to be more expensive because of bigger company overhead. But to tell you the truth, sounds to me like a DIY job with a friend or family member.

To prevent this in the future - treated plywood would certainly help - though plywood will trap any water getting in there, so normally decking planks with a good gap between them works better (assuming the shed has a vinyl floor as you say it does), and they can be bought treated as well. Depend on the plastic shed floor strength, might only need 2x4 or 2x6's with from 1/2" (for drainage and ventilation) to maybe as much as their own width gap between, to support the shed floor.

Also - to keep water out - depending on the shed construction of course, but generally undersizing the plywood a bit and then putting a piece of treated wood around the edge of the decking (fastened to the deck framing and sticking out from it as a ledger board) for the edge of the shed to sit on, and putting flashing or ice and water shield strip at the interface and overhanging the facia strip will keep the water off the deck.

In your case, with the deck already built, you might cut off the rotten plywood in a strip around the outside edge and replace with treated material (like 1x4 or 1x6 which you have treated with Cupreanol or similar copper preservative if you have 3/4 decking, for instance) - putting in cross-blocking or scabbed-on pieces of 2x on the inside of the rim joist as needed to support the joint if you don't need to totally replace all the plywood decking. Then put a strip of ice and water shield or Vicor (that is really what is made for this) in under the shed edge, preferably tucked up under the shed siding if feasible, otherwise with tucked-under doubled over edge toward the inside so it has a slope from the fold to the outside to prevent water from wicking in under to the plywood - then sticking out and overlapping down over the outside of the deck framing as a drip-edge. Could do similar thing with metal dripedge but could be a real ankle or leg-cutter walking close to it. What you are looking to do is basically a drainage path from under or behind the shed siding to the outside of the deck frame like this decking detail, with Vicor or similar replacing the Drip Cap Flashing shown.


To reduce rot potential, use treated wood or treat with copper napthanate or copper napthelate or similar preservative like Cupreanol makes (sold as touch-up liquid for cut ends on treated deck material, in brightish green and dark brown) on the outer edge deck material before putting the shed backk on it, and also all the exposed outer sill/rim joist pieces of the deck. you can also use this every 5-20 years, depending on your weathering situation, to preserve the wood from weathering - also inhibits (prevents if well-soaked) insect attack.

One other thought - if this deck is not elevated off ground contact on blocks or piers or such now, might be a good time to jack it up - even just 2" thick concrete pavers are better than nothing to keep the framing from rotting but do not really inhibit insects at all, though proper deck framing support "hot cross bun" type blocks or at least cinder blocks/CMU's give you better ground clearance and ventilation to keep ground moisture from the decking (especially in snow or cintinuoally wet country) and also facilitate cleaning underneath to remove blown-in debris (though you can screen against that if desired).

Answered 3 years ago by LCD

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