Standing seam metal over built up asphalt tar w/o tear off?

I’ve signed an agreement with a contractor for a bid on 23 square, 12" panel, 3/4" standing seam, 26 ga. metal roof over an aged (but not leaking) 2/12 slope built up asphalt tar roof. Current roof covers irregular height uninsulated garage & eaves (with some isolated minor rot in outside 2x6 T& G at built in scupper downspouts. Contractor says he can level w/ PARTIAL ISO OVER existing roof non insulated areas, ice/water shield THEN the metal panels. He has not yet shared how he plans on repairing the downspout rot from under eaves without pulling fascia board. His plan is to trim existing fascia to matching height.

NOW he is encouraging me to do a 100% tear off, re-insulate w/ 1 1/2" ISO, ice/water shield for an additional 3,500. I'm already over budget at 23k (which included a completed 7.6 square flat roof PVC add on) but some people have now said NO WAY to do steel over tar without dents and summer heat problems. Moderate but wet climate here and the rains have now started. Unlikely to see 5 dry days in a row for several months.

I feel like I’m getting a bait & switcheroo sales job. Should I?

Will the failure to do 100% tear off affect my manufacturer’s warranty of the ice/water barrier or metal roof? What’s the downside to leaving existing roof in place? If tear off is REQUIRED, why not include it in the original bid? Weight is not an issue with 2 x 6 T&G over 4x8 open beams on 4’ centers exposed inside.

I have a new found respect for real roofers now… if it makes any difference. I hope I haven’t left out any details for a meaningful reply. THANKS in advance.

Is this a snaploc panel? 3/4" seems low for a 2/12 slope.

if it is snaploc, i wouldnt use on 2/12…

Self Employed Slave & Kage: Thanks so much for your reply. Manufacturer is “North American Metals” in Banks, OR. I might not have accurately described the panels (1" seam on one end, 3/4" on other) Recommended panels are called the 12 inch “Tight Lock” and pictured at top of page here: (Site refused to allow link to NO spaces: north american metal [period] com/ Products/Concealed fasteners/panels see top of page)

I did call the manufacturer and asked, “What is minimum slope recommended for the 12” tight lock panels?" They said, “2/12 minimum”. Contractor verbally says “Ice/Water to be installed ON TOP OF existing built up asphalt tar and ISO where needed” to level surface over non insulated areas. BUT contract only says, “Install synthetic underlayment over existing roof.” (same thing, right?) " Install pre painted metal eave and rake flashing. Install 26 gauge Standing Seam 12" tight lock panels …".

And now I hear, “NEVER install metal over existing tar”. This site appears to be the best place to get opinions on steel over tar or not.

I feel like I’m working way beyond my pay grade here. I don’t want this thread to descend to that other “just installed standing seam…” thread. I’m just trying to future prevent issues , NOT trying to nit pick.

This whole job is $ 23k and I’d hate to buy a car with as little knowledge as I have about roofs. But I am learning … reluctantly.

I have not challenged my contractor and would prefer staying on his good side. Is there anything I should question him on without being confrontational?

I have installed metal panels in such a manner. 2 x 4’s were added to raise up the panels about 5-6 inches and allow fastening capability too and then a 30# felt over the wood nailers and then the panels. This was a long time ago and new to roofing but the system is still in place on the Mercer Island City Hall building. Must be okay if the State of Washington, city municipality accepted such an install.

For a snaploc system i go 3/12 no less, if they want metal on lower we put in a REAL standing seam roof.

No, synthetic underlayment is felt substitute. Ice and water shield is ice and water shield

Or you can Butyl tape the “pro-loc” seams.
Hank,what do you mean by " asphalt tar roof" ? Is it tar and gravel?


I only know what people have told me… and that is developing into a problem. I am told there are two kinds of tar. Coal tar (used in the 50’s) and asphalt. The roof on this low slope (told it is 2/12 and OK for tight lock standing seam) 1958 house which I have owned since 1980 has no gravel on top. It appears to be rolls of fiberglass saturated heavy tar fabric with a MOSTLY level layer of hot asphalt mopped over it. Twenty years ago, you could not see the seams of the fabric as clearly as you can now. There is little tar material covering the rolls and the seams are not only visible but can be seen to be separating… clearly at the end of it’s life but no leaks visible within house. At the bottom of the eaves, and near rake end, tar is slightly “globbing” and is irregular in height. No insulation over eaves or garage area creates another 2" height variation over the intact, old roof which was NOT budgeted to be removed.

I have contradictory opinions on how perfectly level this existing roof must be since the insulation and accumulation of tar creates variable height. Complicating this system is the built in gutters. The 2x 8 fascia on the eaves creates a dam which is also tarred and I have five 3" round holes drilled in the last 2x6 Tongue & Groove nearest the fascia to accept the tarred in metal downspouts. These have leaked over time creating isolated dry rot mostly very near the downspouts and limited to first or second 2x6 nearest fascia but now the contractor states he does not intend to remove the fascia but merely CUT OFF the top 3 inches (not TEAR OFF) to enable a conventional gutter.

The written proposal which I’ve agreed to addresses costs of possible HIDDEN rot repairs over ONLY the flat roof section (for which I purchased ALL materials since NONE was delivered with installers) and is silent on the VISIBLE rot under the eaves at the built in scuppers. There are no visible leaks or rot INSIDE the house with the exposed 2 x 6 T&G. The flat roof section is now repaired & finished except for the gutters… I hope.

The contractor now volunteers IF I want a complete tear off (bid is for roofing over tar) … he can do that for ANOTHER 3,500 for a total of 26,000 for 2250 sq ft of metal (no dormers, one brick chimney) & the 750 sq ft. of flat PVC (nearly done).

My head’s exploding and with the ambiguities regarding material descriptions, I feel like I’m getting the old bait & switch.

Too much information?

Thanks again to all that have replied.

You could but I dont…

Tear off is necessary to locate any more existing rot I would think. Solution/Corner Cut could be Fluted Decking fastened to rafters directly on top of existing roof, followed by Ice n Water 6 feet off all edges and penetrations, followed by slip sheet, then panels on top of that. But with an existing leak, you cant just go over the top of it and expect it to stop. Only 100% way is complete tear off, rot replacement, Insulation board, InW. Best bet if you decide anything but that, put it in writing, change order to the GC, clarify risk vs reward, sign the dotted line and remove yourself from all liabilty. Best of luck

I feel confident the only rot in is limited to the 2x6 T & G decking under the eaves on the outside one or two boards nearest the fascia where water ponds near the scuppers & downspout openings. Most is very near the scuppers (all 5 appear to be leaking) with one exception but even that is limited to the first board nearest the fascia.

So I’m getting the vibe that many pros think a 100% tear off SHOULD have been in the original bid. If it was, this contractor and this roof treatment would not have been chosen. He was already easily the HIGH bidder but was selected because the standing seam steel was “ONLY” $4,000 MORE than the single ply (PVC like the flat roof) option offered by others. The original bid was already over my budget. I called the manufacturer of the standing seam metal panels, and they say they know of other installations over tar with no ill effects or changes in their warranty.

Should the home owner be expected to pay the entire $ 3,500 of that extra cost to do it with a 100% tear off? Is there any other way to avoid the mess inside the house that comes with a tear off? Is there no way to seal off the exposed roof edge if the outside eave is opened up?

Work has stopped while it’s raining and I am currently waterproof. I’m told the contractor is busy with emergency calls… surprised?