I need to re-roof, and up the insulation in the ~ 500 s.f. roof shown below. Rafters appear to be 2×12’s tapered down to about 2×6, and insulation is only whatever fit in 2×6’s about 40 years ago. To avoid the mess and destruction of the interior, I’d like to put 2″ XPS directly on top of the present roof (roll roofing, I think), followed by 1/2″ wood fiber board (from the EPDM supplier), with EPDM glued to that. My questions:
1. I’m thinking I need a ‘curb’ around the perimeter of the XPS, for the EPDM to wrap over. My plan is to nail or screw 2″ high wood strips for this. Reasonable?
2. No 2 1/2 ” plus, plastic cap nails around here, for attaching the XPS. Do I need to find screws and plates (difficult), or maybe buy long enough nails and take the caps off of the shorter nails that are available, and put them on the longer nails?
3. The back corner of the picture shows a shingle roof overhang. If I build up about 2 and 1/2 ” with this plan, I’ll be below that overhang only about 1/2″ at the point of that overhang (2 1/2 ” futher back, where it meets the other roof). Is that a problem?
Thanks for your help.
Thon
Replies
1 - sounds like a plan
2 - best to tear off to decking first, but either way, you can use dabs of PL 300 to glue foam down. use plates and screws through it all for the fibreboard. If you can't get them, the supplier has no business selling EPDM or fibreboard products
3 - anything canm be flashed when you know what you are doing. I can't open a jpeg that darned big
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Attached is your pic in smaller form (for the download challenged).
I don't think I'd just nail or screw that fiberboard down without using the discs. They work kinda like washers, spreading the load and helping to hold it down. With just a nail/screwhead, you run the risk of it punching through.
There was a FHB article a month or two ago where they put EPDM down on a balcony. I'm pretty sure they used the discs.
As piffin said, your EPDM supplier should be able to supply the discs. I don't remember them being expensive...certainly no where near the cost of the EPDM or the EPDM adhesive. If you don't have a roofer nearby who carries them, you can probably order them online.
jt8
From that photo, it looks like the surface is fine to go over without tearoff. The main thing I see to tear open is the siding at the gable end - to get in under it with the EPDM
Is this a pic of somethiong youposted a couple months ago where it once had an electrical service wire atached over the door?
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
Thanks for all the feedback.
The supplier does have the hold-down discs but they're 300 miles away, and I was, shall we say--too frugal (?)-- to get them while I was there. I can try and find some closer but am not optimistic. I've thought about trying to make some but don't know how I'd get the depression for the screw head. Weather is supposed to cooperate --for a change--this weekend, so was hoping to get this done in the next few days. May have to have someone overnight them if you think that's the only good option. (Hmmm, something about penny wise, pound foolish??) Do 3 and 1/2 inch screws (2" XPS and 1/2" fiber board) sound right?
Read the FHB article--several times.
Will get under the siding on the gable end--only extends out about 2 feet.
The pictures a couple months ago were the roof of an addition on the other side of the house--and it's been quite a...a... a..... learning experience. Yeah, that's the word. Found 2x4 rafters spanning over 10 feet, so tore them out and replaced with 2x10s for insulation benefits. Was supposed to have help but that (unavoidably) dried up so with winter moving in and 2 predicted days of sun and 60's started in. With the new rafters in, was just able to lay some plywood up there and unroll some felt paper prior to rain and then snow. That was over 2 weeks ago and the weather hasn't given me the 2 clear days I think I need to finish, since. Leaks have been sporadic but not torrential--and fortunately that room is a utility room/porch. Wife hasn't been terribly happy being an assistant every now and then either. <G> But, it's now ready for sheathing around the taller rafters, then the fiberboard and EPDM. Hope to get BOTH roofs rubberized on Saturday (help is supposed to show up)!
I priced ISO when/where I bought the EPDM and they quoted me something like 20 bucks a sheet for 1/2"--said the price had skied recently.
BTW, would you overlap the felt paper any more on a low slope roof, than usual?
Thanks again.
Thon
If you can't get the regular dimpled discs you need, go to a hardware store and pick up the largest fender washers you can find. The hole will still be small enough to trap the screwhead and clamp the fiberboard. You could even try to dimple them with a large punch or chamfer them with a drill bit or countersink but than would be a lot of extra work.
Evan Home depso has 1.5" Iso at 21$ foil faced R-Max
easy washer= roofing felt nails with metal caps not pllastic
I would take a look at the higer R of Iso sheets comonly used in flat roofs, available up to 4" in 1/2" increments that I'm aware of. Harrington in SLC had lots last time I was there, plus good pricing.
4x8' x3" was 21$