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.