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AikiPapi 07-28-2010 12:19 PM

Drainage for Plastic Shed on Wooden Platform
Hi All, and thank you for sharing so much of your experience here with DIY newbies like me. Hoping to contribute myself someday! Until then, my first undertaking now has me a little unsure and I'm hoping someone can help guide me.

I'm currently assembling an HDPE Lifetime Shed (8' x 15') on a wooden platform I have slowly built over the past few weeks. Although Lifetime Co. does include some foundation suggestions, I decided to beef up their model 2x4 frame sitting on pea gravel to a 2x6 floor/deck frame (24" OC) plan I got from, using their patented notched pier blocks. I believe I got that idea at least partly from this site - thanks!

In any event, in deviating from the Lifetime instructions I missed the point about drilling three 1/2" holes for draining into the plywood subfloor between each joist. Needless to say, it rained hard before I cold get the roof up on the shed and despite my best effort to cover the open shed with a tarp, water accumulated between the plastic shed floor and the plywood beneath. Surprisingly it did seem to clear out (evaporate?) in a day or so with our recent 90+ degree temps in NJ, but now I'm wondering if it makes sense to go back and dis-assemble the shed floor and walls to put those drain holes in.

All of the wood used is PT including the 3/4" CDX plywood subfloor and the floor sits almost a foot above ground with the pier blocks so ventilation underneath should be adequate. By contrast, the Lifetime floor plan has the 2x4 frame sitting directly on the ground.

So now I'm trying to envision how/if water might accumulate this way again once the roof is actually on, since the platform is almost exactly the same size as the shed floor (maybe 1/2" excess platform in the worst spots) and the opportunity for rain to accumulate and run under the shed floor from that tiny lip seems minimal. My understanding though is that the glue used between the layers of PT plywood is impervious to water so anything that did get stuck between the flooring might sit awhile.

Q: Can someone help me understand if it makes sense to go back and make this adjustment to the plywood subfloor or whether it's not really necessary given what I've built?

For reference sake, the Lifetime assembly instructions are linked below with the wooden foundation plans on Page 19:

Many thanks in advance for any insights you guys can offer!

DangerMouse 07-28-2010 02:52 PM

I can't download a 24 meg pdf on dialup, so I can't see what the plans call for exactly.
Why would they want drain holes in an inside floor of a shed?


AikiPapi 07-28-2010 03:14 PM

Hi, DM.

Basically the platform plans call for the same 3/4" PT plywood I used over a 2x4 (18" OC) frame, all of which would seemingly sit on the ground. They then suggest drilling a number of 1/2" drainage holes into the plywood "sub-floor" before laying the shed's plastic (HDPE) floor planels on top of it and buildng the shed up. I modified the plans a bit as noted below, but it seems to me those drainage holes would be most useful if you got caught (like I did) with a storm mid-build. I am struggling to see the value of them once the roof is on the shed.

Granted the Plastic floor panels do not have water-tight seals between them so if something were to spill insde the shed it would probably make its way down to the plywood pretty quickly (and possibly get trapped) if not cleaned up, but I'm only using the shed to store patio furniture in the winter, a snow blower in the summer, etc.

Does this make sense?

Thanks again for your time....

Ron6519 07-28-2010 04:00 PM

It seems you have multiple(6) panels that clip together. These seams are probably not water tight so the holes are for drainage. If you put the snowblower away with snow on it it will melt and filter through the seams. Even PT ply will rot.
I don't like the hole scenario. I would seal the plywood deck. Maybe with ice and water shield. I would tilt the deck platform to the rear so the water would drain out and install a drip edge so it fell away from the platform edge. If need be, I'd make sure the plastic flooring had weep holes in the back so the water had easy egress.
I would also caulk the floor seams with a good quality silicone or poly caulking. This would minimize how much water got through the seams.
There's an admonition about sharp objects on the floor which would speak to this sheds questionable longevity.
If I could, I would find a way to remove the plastic floor from the equation if at all possible. I'll leave you to going through the 44 pages.

AikiPapi 07-28-2010 04:14 PM

Thanks, Ron. Caulking the seams between the plastic floor panels makes good sense to me and was suggested by someone at the shed manufacturer as well. Not sure how tilting the deck platform and taking everything out of level wouldn't create even more problems for me though as all the guidance I've received so far is to make sure the foundation is level (and I've worked hard to get it so!).

Sealing the plywood subfloor also makes great sense but since that has me dis-assembling the floorpanels and half the walls to do it, I guess I've got to determine if disassembling is worth it and if so, whether to go the drain-hole or sealant route (or both).

AikiPapi 07-29-2010 08:01 AM

Forgot to mention here that I dont think it's possible to take the plastic floor panels out of the equation as the walls snap into them and build up from there. I'm leaning heavily toward just sealing up the gaps between the floor panels as best I can (and possibly around the exterior base of the shed as well).

Does anyone else have experience with this kind of shed set-up and what (if any) special drainge might be called for?:huh:

ericb1960 07-29-2010 10:22 AM

One thing you might do is drill a few holes through the floor and subfloor and then epoxy fill the top hole.

These sheds are known to be durable. I think the warning about the sharp objects refers to things like dropping the pointy end of an anvil onto it.

AikiPapi 07-29-2010 11:35 AM

Thanks. I had been considering something like this and was trying to picture how I might be able to patch-up the plastic floor (if I have to drill through it) without re-sealing it to the plywood subfloor. I'm assuming there must be away to accomplish this as you describe, but it's not clear to me how I could get a sealer like that to adhere to only the plastic layer.

If I can figure it out (or you have a tip to share), this does sounds like a good 'Plan B' if sealing the plastic floor seams doesn't work well enough and I feel trapped water under-foot after the next big storm. Does this make sense?

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