Adhesive

Steel roofs, at least the ones I see down here, typically have ridges where adjacent panels are joined together.

Have you considered making some form of clamps that could be secured at these points?

I have no idea of what you are trying to do as far as a load goes, but you could make a set of large flat anchor plates that the brackets could bolt to. Then silicone the plates to the steel roof.

The idea is to increase the mating surface areas as large as possible to maximize grip.

How much flat contact area per bracket? Picture of bracket?

Is the bracket plated? Painted? Are you trying to bond the bracket to paint, or metal? (You said painted steel. Are you removing the paint?)

How will failure stress be applied? Peel, tension, torsion? Compression? How much force/weight?

Give us a chance to help.

In lieu of any further information, I'd use a slow curing two part epoxy.

You'll get as many different "perfect glue" recommendations as responses here. For some reason many people here fancy themselves adhesive bonding experts, which they're not. (AH, post #1, is an exception to this)

Good luck.

What about spot welding studs , long nuts or standoffs to the sheets?

I've had good success with JB WELD. The gremlin in your question is "painted surface"

JB Weld is an epoxy type product that should hold up to the temperature swings.

GA

How true, how true.......

I use meths or denatured alcohol to clean surfaces, never to touch them again before gluing.

Paint should never form part of the bonding for me personally, though possibly Epoxy paint might be OK.....though I cannot say that for certain....

The larger the area of bonding, the greater the strength.

First of all, thanks for all of your input. Let me expand on my project -- I live in Holland, MI with 111" of snow per year. My house has overhangs that build up ice dams on them due to the lack of proper air flow through the eaves, which is another project altogether; I have used venting, insulation, etc. and still get ice dams. Last year, I attached flat aluminum brackets (1/2" x 2") that came with a roof heating cable in a v-shaped pattern to my roof using automotive bodyside molding tape, assuming that if molding won't fall off of cars through car washes, winter, summer, etc., the molding should hold the brackets that attach the electrical cable. All was great until the spring thaw -- the cables eliminated the ice dams all winter, but the tape gave out during the spring thaw.

Because the cable worked so well, I want to use a different adhesive to make the attachment permanent, which is why I joined the blog here at CR4. FYI, I prepared the roof by using 000 steel wool to remove dirt from the steel, and used rubbing alcohol to clean it before applying the tape.

I have found a high performance silicone neutral cure product called "Rain Buster 14000" from Top Industrial Inc., but am unsure if silicone sealant/sdhesive caulk will perform. I appreciate your help :)

GAW

"When all fails... use big bloody nails"

rather than an adhesive I would go with drilling and pop riveting making sure that the hole and rivet is well encapsulated with silicone.

Vince

Pop rivets are generally aluminium and therefore subject to corrosion outside (made worse by the steel plug left in after usage) and are weak.......

If there are available Pop rivets in stainless, it may be ok......

The OP wanted no holes though......

Your roof is hot zinc coated steel sheetmetal, that - in all likelihood - after a few years can be painted. To hold it down to the roof, stainless screws are driven into the ridge with sealing washer. This screw is fairly electrocompatible with the sheetmetal. On the other hand aluminum is corrosion big time for the roof! If you insist using the alu brackets, they need be strictly insulated from it! Or there will be rusting in the roof within a single year. While a properly maintained roof lasts 35-50 years.

Since the cable has the function to keep the low edge warm enough, I would look to clamp the cable to the bottom side edge of the sheet metal. That way the snow can slide off the roof without ripping off the cable.

Here idea.

3M VHB Tapes this stuff good. There are several formulas with high temp range capacity and most can handle low temp. It can be used in-place of mechanical fasteners.

Permanent Assembly Tape this category you should find just what will work in your app.

Here a pdf tech guide.

I've worked with stuff on&off over the years. I have been surprised how well its worked in some apps I've used it for.

All the usual disclaimers, just a user.

The issue here is time. Time to fix the real problem with your roof. Ice Dams come from the melting of snow off the roof covering the heat area of coverage. Loss of that heat through the insulation (or lack of) causes the snow to melt and run to the lower end of the roof. There it is re-frozen at the eves and begins to form what we all call ice jams. The electric heating elements are used to mask this issue in cold weather climates such as yours. Adding more insulation to the heated portion of roof area or changing the roof color to a light shade will help prevent this issue.

you could add steel to the aluminum brackets and then just Weld them and paint the welds.All done,nice job and strong, No Mickey mouse job

Welding is something I would not want the liability doing.

The heat required will surely melt and/or ignite whatever material is under the steel.

The biggest impediment to welding, in my mind, would be the thinness of the steel roofing.

It would be like welding auto body sheet metal. Not impossible, but certainly not dooable with a stick welder.

No, I would think a stud type welder used in the auto industry would be the best ticket.

BUT - you still have a risk of fire.

I would sooner drill a hole and use a standard fastener with the proper roofing sealant. That technique works and has a long track record of success.

Since you have a steel roof do not use the aluminum clips due to galvanic action.

Instead, replace the clips with either galvanized steel clips or stainless steel clips.

Use STEEL pop rivets to secure the clip to the roof....follow-up with a premium exterior grade silicone chalk intended for roof repairs.

I wouldn't bet my last dollar on any adhesive holding those clips to the painted roof surface because that's the weak link in the chain.

I feel your pain in regard to those nasty ice dams occurring on your eaves. We had them here as well.....IN SPADES....we suffered from over $50k of water damage (not including losses to contents) to the house and are still trying to wrap-up the reconstruction mess. This week I hope to finish installing the new ceramic floor tile in the Kitchen & Dining Room! Hooooorayyyyy!!! Then the new roof heating cables get to be installed, finally!

I have a standing seam painted roof in snow country. I intend to use the 3M VHB tape to attach aluminum angles to the roof to prevent large snow slides in the areas over my doors. The VHB tape is a good product, its foam backing assures adhesives contact with the roof surface, insures galvanic isolation & allows movement between the steel & aluminum that might occur due to expansion/contraction differences.

Hi Doug, thanks. Have you had experience with this tape holding up through a northern winter?

Hi gaw, in my post #8 there a pdf link to a tech sheet on the different 3M VHB tapes.

Most of the tapes have a max temp range -35C to 110C.

With the correct tape will stick to most surfaces. Prevent dielectric galvanic problems. Have good load holding power at temp. with proper selection. Also I think 3M has a good help with tech applications/problems/questions.

Just like any other type of fasteners proper selection is important. The amount of tape matters, cleanliness, surface prep.

Here a few excerpts.

"3M™ VHB™ Tapes provide the convenience and simplicity of a tape fastener and are ideal for use in many interior and exterior bonding applications. In many situations, they can replace rivets, spot welds, liquid adhesives and other permanent fasteners.

These 3M™ VHB™ Tapes are made with acrylic foam which is viscoelastic in nature. This gives the foam energy absorbing and stress relaxing properties which provides these tapes with their unique characteristics. The acrylic chemistry provides outstanding durability performance.These tapes utilize a variety of specific foam, adhesive, color and release liner types to provide each product/family with specific features. These features can include adhesion to specific or a broad range of materials, conformability, high tensile strength, high shear and peel adhesion, resistance to plasticizer migration, and UL746C recognition.

All 3M™ VHB™ Tapes have excellent durability and excellent solvent and moisture resistance.

Note: All 3M™ VHB™ Tapes should be thoroughly evaluated by the end user under actual use conditions with intended substrates to determine whether a specific tape is fit for a particular purpose and suitable for user's method of application,especially if expected use involves extreme environmental conditions or high dead load stress."

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"Use the right amount of tape: Because 3M™ VHB™ Tapes are viscoelastic by nature their strength and stiffness is a function of the rate at which they are stressed. They behave stronger with relatively faster rate of stress load (dynamic stresses) and will tend to show creep behavior with stress load acting over a long period of time (static stresses).

As a general rule, for static loads, approximately four square inches of tape should be used for each pound of weight to besupported in order to prevent excessive creep. For dynamic loads, the dynamic performance characteristics providedon page 4 should be useful, factoring in the appropriate safety factors.

Allow for thermal expansion/contraction: 3M™ VHB™ Tapes can perform well in applications where two bondedsurfaces may expand and contract differentially. Assuming good adhesion to the substrates, the tapes can typicallytolerate differential movement in the shear plane up to 3 times their thickness.

Bond Flexibility: While an advantage for many applications where allowing differential movement is a benefit, thetape bonds are typically more flexible than alternative bonding methods. Suitable design modifications or periodic useof rigid fasteners or adhesives may be needed if additional stiffness is required."

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Hope this helps.

Hi Gaw

Not Yet.

I am VERY sceptical that a glue with such a small temperature range, will hold on a roof, with its possible vast temperature range......

I feel that a hard setting glue is needed, something like Epoxy or similar.....is needed.....some Epoxies can hold at up to 400° (°C I believe, but even if only °F, that's still a high temperature.....).