8 Soldering Tips You Should Know
Soldering, with regards to roofing, is the process of joining two pieces of metal together using solder to create a leak proof seam. When you get started soldering, it may seem difficult to fill the joints properly while maintaining a degree of professionalism. Gobs of solder everywhere is not appealing. Learning how to use solder to make water tight seams is a good skill to have. Excellent resources can be found at the Copper Development Association website and Revere’s Copper and Common Sense. Thanks to Tony Vizzi of Specialty Copper Roofing of Pottstown, Pa for use of the photos. We’ve assembled tips on how to give you an edge over your competitors.
Soldering Tips
1. Cleaning the material is EXTREMELY important to a good soldering job. I cannot stress enough the cleanliness of the metal you are attempting to solder and its effect in attaining a great functioning and a great looking seam. Use a wire brush or another abrasive to strip the metal bare on both sides of the seam. Don’t take this step lightly because solder will not adhere to oxides.
TIP: Solder immediately after fluxing.
2. Pre-tinning Joints may be the key to longevity in your work. Joints that are pre-tinned and then soldered have tested to average 40% stronger than ones that are not pre-tinned (Copper and Common Sense). This is due to the fact that pre-tinning your sheets before lapping actually will allow 4 layers of copper to have solder flow, while generally the flux alone will only draw flux to adhere to 2 layers.
3. DO NOT ATTEMPT TO RE-SOLDER A BROKEN SEAM! If a solder joint has been broken, moisture and dirt will enter inside over time. This causes the solder to oxidize which makes soldering a new joint a bad idea.
4. Few materials used will solder as easily as copper:
- Copper. When working with 20oz copper or less, locked and properly soldered seams will be as strong as the copper itself. When dealing with 24oz copper, seams should be lapped and riveted, then soldered for waterproofing if necessary.
- Stainless Steel and Aluminum have oxides form on their surface that are very difficult to remove in order for solder to adhere. Each material requires their own unique flux.
- Zinc has a relatively low melting point and therefore is not ideal but still can be soldered. Here is a detailed PDF on soldering VMZinc.
- Galvanized steel has poor thermal characteristics but can still be soldered using the proper steps.
- Lead coated copper should be soldered with 60/40 lead tin solder.
5. The proper flux to use depends on the material you are soldering. Soldering flux serves one main function in joining roofing materials, it is meant to prevent oxidation of the metal which causes poor adherence of solder. Certain metals will require a more aggressive or acidic flux to achieve a proper joint. Don’t forget to wash your seam with soap and water to clean off any leftover flux that can corrode the metal.
6. Stay away from roofing torches for soldering purposes! The open flame can leave burns on the material and is a messy way of soldering. Not recommended. Roofing soldering irons have enclosed flames and constant heat is applied to the copper tip. This is preferred over the hand irons which will lose heat.
7. A helpful tip when using a propane soldering iron is to turn down the heat of the iron once the tip reaches temperatures that melt solder. This will preserve the life of the copper tip. This is especially important when working with the long life tips which require no filing.
8. Dipping a heated copper soldering tip while in use into a 1/2 mix of water and 1/2 ruby fluid is a good way to remove any debris from the tip which causes dirty joints.
Picture taken out Copper and Common Sense by Revere. This is the one of the most comprehensive resources available on metal roofing.
This is a video on Flat Lock Soldering by Larry Peters and the Copper Development Association.
I have a flat lock seam copper roof over my porch about ten years old and it leaks. The joints look like they were made with a torch not an iron. I do not have the money to replace, so what is the best way to repair ? your help is appreciated .
I would fully adhere EPDM (rubber membrane) right over it
It’s pretty frustrating trying to find out how to solder a butt joint on sheet metal, on the internet. The information is vague and I’ve been lead down the wrong path a few times now. Is there any way I could get a straight answer as to how a newbie like me can fuse two pieces of sheet metal flashing? It’s galvanized, I believe, and is 28 gauge.
Regards.
I don’t think it’s a good idea to solder a butt joint at all. You’re better off to have a mechincal joint like an “s” lock or flat hook on the pieces. It depends on what you’re doing with the piece.
Please read up on “galvanic corrosion”. Anytime you place dissimilar metals in contact with each other, in a liquid medium, one of them will corrode. That includes copper, aluminum, stainless steel, iron, zinc, lead, etc.
This is why they coat iron with zinc – in contact with iron, zinc will corrode first, so all the zinc will corrode off first, before the iron will start to corrode, which a why they call the zinc a sacrificial anode.
Which metal will corrode first can be determined by looking at how reactive it is on the Pauling scale. The values for common metals are:
Magnesium 1.31
Aluminium 1.61
Zinc 1.65
Iron 1.83
Lead 1.87
Copper 1.90
Any metal with a low number will corrode first, so zinc will corrode first when in contact with iron. Iron will corrode first when in contact with lead, etc. The larger the difference in these numbers, the quicker the corrosion will happen.
What is interesting is how reactive aluminum is. What saves it is that it is so reactive that it reacts with oxygen immediately and the resulting aluminum oxide costs the material, giving it a protective coating. The only way to solder it is to cover it with oil to prevent the oxygen getting to it, scratch off the aluminum oxide coating, and then solder it under the oil. The downside to soldering aluminum is that it is much more reactive than lead, so the aluminum will start to corrode (this is the white dust that you see).
Bottom line is know that dissimilar metals in contact will corrode and either electrically isolate them from each other (e.g. use a rubber washer and nylon screws to connect them) or keep their Pauling numbers as close as possible to each other to reduce the corrosion if you do have to place them in contact.
This is quite different from electronics soldering. Learn something today. Bookmarked for sharing.
I’m grand now I have experts to consort, and in fact exchanging ideas, thanks for the web it’s helpful.
Looking to use a stainless steel perforated sheet metal for a hip vent on a copper standing seam roof. Our plan is to clean the copper roof panels, and the solder the stainless steel sheets to the copper, then build the hip vent off of that.
– any advise of soldering copper sheets to stainless steel sheets?
– what flux should be used ?
– will a 50/50 solder be ok to use ?
Another way would be to hale holes drilled in the upstand of the copper on both sides and solder brass mesh instead of perforated stainless. Just food for thought.
My company uses “M-A” flux liquid by Laco for our copper work. It’s made for stainless steel, but works for copper. I researched it once to make sure it didn’t adversely affect the copper. Can’t find the reference right now. I’ve never tried it on stainless steel. Let me know how it goes. (http://www.laco.com/soldering-fluxes/m-a-flux-liquid/)
… reply to this one so I get notified. thanks
Works on stainless like a dream i have only used it o. Roofinox stainless steel and it does a great job. I got it in a soldering demo I did for roofinox company the representative gave me a bottle and I been using it on my copper and it doesn’t leave heat marks like stay clean or other fluxs I have used .
Do not
Stainless in close proximity to copper will cause the copper to corrode
Find a perforated sheet of brass
This is really a great informative post!I learn more important things. Thanks for sharing.
Ok, firstly, you guys are good. Just to add something I have done roofing for over 30 years in Australia and have learned a few things, firstly Mr. Mark Allen is correct and well informed, dissimilar metals have a charge that react to each other depending on what they are in contact with ( think batteries) and in the case of joining the same or dissimilar metals a membrane in between can be used. Here, for instance, with massive box guttering etc a 20 to 50mm overlap is employed with a neutral silicone layer and a double row of staggered silicone covered rivets generally last for many decades.We stopped soldering gutter joints more than 30 years ago when non acetic silicone was developed to keep the tiles on the challenger, it wasn’t the stuff they used but cheap to make products that changed the sealant/heat/glue industry dramatically.
For stainless steel – use phosphoric acid (about 10% seems oK) – great for soldering battery cell terminals as well – you need very little, and it washes off.