Need some advice on fixin my old shop roof


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I've got a janky garage/shop roof that I'm trying to get ready for the winter, and need a suggestion for some kind of filler material.  The guy who built it was in the military probably in the early 60s and it seems like it was built to the standards of a field manual.  The roof is sloped about 3 deg, which when it was new probably performed well, but a number of decades later and it ain't lookin so hot.  Everything's under control insofar as major structural integrity is concerned.  The problem is with some of the plywood that droops in spots between the joists.  I'd like to secure a large tarp up there to give it the best chance possible over the winter, but if these dips aren't filled in before the tarp goes on there's gonna be lots of places that will harbor shallow pools of water weighing on the roof all winter.

What I have are a number of say 3 ft long runs between joists that are sunk about 2", and these are the places I'm trying to fill.  My first idea was to use expanding foam but emptying out a can doesn't nearly fill one of these dips.  Something with more volume is needed.  So then I had the idea of using mulch, but that's got too much potential to absorb moisture and become too heavy.  Thought about sawdust, but it's got the same potential to gain weight.  And now my last idea is to use shipping peanuts.  Although I don't think they'll end up being what I go with because of their cost and anticipated difficulty in working with them, they do happen to be a good example of a material that would fit the requirements of being light and resting absorbing water.

So that's where I'm at with this guys.  Any ideas on some kind of filler material I haven't thought of?

Last thing is, I'm trying to figure out a material I could cut to about 3'x5' and use as an outside tabletop, something that rain won't effect.  3/4" melamine would work great insofar as utility is concerned but obviously wouldn't work due to not being weatherproof.  Any suggestion for a material here?

Thanks.

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Filling dips and then covering them with a tarp sounds like just a heap of problems in the making. I'd say avoid doing that at all costs. Tpt is right, but it's late enough in the season that's probably not an option. A good fresh tarp can probably handle the standing water, and if it's going to sit in place that'll happen regardless of what you do trying to fill in those dips from the outside.

The last thing you want to be doing is trapping moisture against what sounds to be a nearly failing roof system (guessing membrane?). If you have a handful of spots you're really worried about, maybe consider throwing some sheets of corrugated roofing over them temporarily to shed the water, but that's still not a great idea.

Edit; actually, thinking about this more, I think I've seen people put down pressure treated 2x2s or similar sleepers, parallel to the slope, which could help channel the water down the tarp and reduce pooling.

As for a completely waterproof tabletop you're pretty much  looking at metal (stainless or aluminum), stone (or concrete), or plastic. Might try calling around any local countertop or architectural salvage places to see if they have extra corian going cheap.

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  • 3 months later...

My suggestion for a filler material would be a lightweight, water-resistant foam. This can be found at most home improvement stores and can be easily cut to size. Another option could be a rubberized sealant, which can be applied with a caulking gun and will also provide a water-resistant barrier. As for the tabletop, you could consider using a weather-resistant composite material such as Trex or a marine-grade plywood. I think that a company like top Indianapolis roof company for you would be able to do the job well.
Best of luck with your project!

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What's going to keep it from continuing to sag?  I wouldn't chase the current design.  Simplest would be more suitable sheathing over what's there.

I'm working on such an addition right now.  It's a storage shed built onto the side of an odd building here that came with a house we bought.  It has an asphalt shingles on an almost flat roof.  I saw the roof sagging, so I cut the old lock off the door.  Everything in it is soaking wet and rotten.  I have a guy coming to get the stuff in it for scrap metal tomorrow.  I did find a completely intact and unopened bottle of Chlordane insecticide in there, and a couple of old plastic gas jugs like I like that aren't available any more, but absolutely nothing else of value.

Right now, I'm undecided whether to push it all down with the tractor, or build another roof on it.  It's only about 6x12 feet, and 6 feet tall.  I don't care a thing about having the room, but the question is whether it's more work to tear it down, or build a roof on it.

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3 hours ago, Tom King said:

Right now, I'm undecided whether to push it all down with the tractor, or build another roof on it.  It's only about 6x12 feet, and 6 feet tall.  I don't care a thing about having the room, but the question is whether it's more work to tear it down, or build a roof on it.

I vote tractor. Sounds like much more fun!  :D

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I had enough leftover sheets of old tin, and cover sheets from buying it in years past to wrap it up.  I put some heavy scaffolding boards on it to hold it down.  Hopefully, it will dry out under this, which will make it a lot better to tear off than soaking wet.

Fortunately, the rest of the roofs on that building are in good shape.  There is a Big dip where those rafters are collapsing.

I hate a flat roof.  I'm going to put a sealed standing seam roof on this one.  It's not like I don't have better things that I need to do, but this will only get worse, and make more work if I don't fix it now.

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