Box gutters can be found on many older homes, multi-family dwellings, old stores, factories, etc. They were by and large one of the most popular rain collection devices built into and onto structures built between 1880 and 1925. Box gutters date back much farther than 1880, as they can be found on very old buildings in both the USA and Europe. These time-tested gutters are still being built and re-built today.
A box gutter does not hang onto the edge of a roof or on the edge or side of a house as many modern pre-formed metal gutters do. A box gutter is actually built into the bottom of the roof or into the roof overhang. The foundation of most box gutters is wood that is then covered with thin sheet metal such as tin, copper, lead, stainless steel, or some other metal that will not readily corrode.
The shape of the box gutter is created by a skilled carpenter as the shape and slope of the gutter is completely controlled by this craftsman. The sheet-metal trades person follows and simply shapes the metal to match the wood gutter.
Tin-coated steel is perhaps the most common metal used for box gutters because it is affordable, is easy to form and solder. Copper would probably be the second most-popular metal to use as it is very easy to bend and solder. Copper also has another advantage in that once installed, it never requires any maintenance. Tin-coated steel must be painted immediately after it is installed and then repainted every 8 - 10 years after the original installation.
Here are the specifications I would include in a contract:
- All wood that forms the gutter must be in good condition and securely fastened. Replace any and all rotten wood on re-lining jobs.
- The wooden structure that creates the gutter must slope to the outlet hole in the lowest point of the gutter.
- The slope must be uniform and designed so that once the gutter is lined with metal and all seams are soldered, water readily flows to the outlet hole and puddling is minimal.
- Use 40-pound tin-coated steel or solid copper roll.
- All seams where one piece of metal connects to another must be constructed with an interlocking-S seam. The width of the interlocking-S seam shall be a minimum of 3/8 inch.
- All seams shall be lightly tapped flat, but not so flat as to impede solder from flowing into the hidden areas of the seam.
- All interlocking-S seams shall be soldered and the molten solder once hardened, must be thick enough that it completely covers and hides the interlocking-S seam.
- If tin-coated steel is used, the tin must be carefully cleaned with rags soaked in mineral spirits or paint thinner. All mill oil and all soldering flux must be removed from the metal before a special metal primer is applied to the tin-coated steel. A finish coat of paint must be applied within 24 hours of the primer application.