Guide to Building a Copper Countertop
Professional chefs have preferred metal countertops for decades due to their anti-bacterial and stain resistant properties as well as their durability. Copper is a unique material for a countertop, not only for its color, but also for the fact that it changes over time. Since copper is a soft metal, it can be dented if heavy items are dropped on it and knives will scratch it. Sealing the metal will reduce it, but not eliminate them completely. You can opt for a textured surface to reduce their visibility.
Eskay Metal Fabricating
Copper.org has listed many advantages for using copper as a building material for the kitchen. A few of them are:
Unsealed, it provides an antimicrobial surface 30 times more effective than stainless steel. E coli survived on stainless steel for 34 days while on copper it lasted for only four hours.
Unsealed, it provides a "living" surface that will change colors over time, depending on what it comes in contact with -- most often; it will go to shades of brown.
Sealed or regularly polished, it will remain a shiny salmon color. If sealed with lacquer, it will like require periodic resealing to maintain its look.
Copper sheet is sold by ounces per square foot. 16 oz or 20 oz copper should work fine.
Seams or miters are easily soldered and may be tinted to match surface, ensuring no leaks or cracks.
Seams or miters may be welded (Brazed) and polished providing completely seamless appearance and performance.
Other metals that can also be used besides stainless steel and copper are zinc, pewter, and bronze.
Sizes of Copper
You need to know some terminology when looking to purchase copper sheets or coils.
20-ounce copper (20 ounces per square foot) is also known as 22-gauge. It is also known as copper sheet or copper plate. C110 is the technical name for a common alloy. These sheets can be purchased in sizes up to 36” x 48”. They can also be custom cut and ordered online at https://www.onlinemetals.com/ .
16-ounce copper weighs 1 pound per square foot and has a gauge slightly over 23.
When using copper to construct a countertop there are several issues you need to resolve before starting. Seams, adhesives, nailing, and base or substrate material is discussed.
Seam location must be considered just as with high-pressure laminates and granite. With copper you can do several things; tuck, solder, and braze. Seams on inside and outside corners will need to be tended to, but do not necessarily need to be soldered or brazed. They can be rolled and hammered to create a rounded edge.
To accentuate the seams you can cut a narrow slit in the substrate, plywood, and bend and tuck the edges into the slit. This will create a cleaning problem and you need to fill the slit with a small amount silicone to protect the wood beneath from any water that may enter the seam.
Soldering and Brazing Seams
These two methods are preferred since they will make a permanent seam. After the soldering or brazing is completed the area must be cleaned completely and possible ground down with a small belt sander or grinding tool.
It is recommended to use at least ¾ inch plywood for the base of the copper countertop. I would suggest using 2 layers. If you want the edge to appear thicker than 1-1/2 inches you may want to add a strip of ½ inch plywood around the edge, but most people are happy with a 1-1/2 inch thickness. If you choose to go with only one layer of plywood, you will definitely want to add a ¾ inch strip around the perimeter of the countertop.
The two layers of plywood should be screwed and glued together with the screws countersunk. The screw heads should be filled with wood filler and sanded flush. Use stainless steel screws.
Adhesives and Nailing
Most metal countertop manufacturers recommend gluing the copper directly to the substrate. Some consider nailing the copper edge that is wrapped around the plywood from the underside, but this can cause the surface to “tin can.” Tin canning is when the metal expands and bulges away from the substrate and if you push on it will make a popping sound like when you gently squeeze a can. For this reason it is best to use construction adhesive like Liquid Nails or floor tile adhesive.
Even if you use adhesives, you should purchase copper nails from a roofing supplier and nail the rolled over edge. Since they will not be visible you can use either roofing nails or fascia nails. Do not use steel or galvanized nails since you will create a cathodic reaction and cause the nails to corrode.
The closer the metals are to each other, the lower the reaction.
The Nobility of Common Metals
5. Stainless Steel - Active
9. Stainless Steel – Passive (Normal state)
Besides the common woodworking tools to build the plywood substrate, you will need the following:
Metal Brake (not necessary, but will produce sharper corners)
Forming the Sheets
The most labor intensive part of the job will be forming the folds and bends in the copper sheets. The best way to accomplish this would be to rent a sheet metal brake for about $30/day. It is basically a long metal ruled clamp with a piece that is lifted up from underneath to form the bends.
You may want to practice with some scrap aluminum until to get the hang of it. Make accurate measurements and consider making a paper template complete with the folds to locate where the bends are to be formed. Once you place the copper on the substrate you may want to use a rubber mallet or block of wood to tighten up the corners. You will want to leave the last fold that will be bent under the countertop straight and form it by hand by pressing a 2x4 block on the sheet and rolling it up under the edge. Wait until the adhesive has set to prevent it from sliding.
As stated before you can either seal the copper with a lacquer or leave it unsealed or raw. A unsealed surface will have antimicrobial properties where the sealed one will not. You will also have to reseal it periodically and work areas will wear faster and change color prior to sealing. You may also want to wax your countertop or if you are a glutton for punishment, you can use a polishing cleanser like Bar Keepers Friend.
As an alternative to rolling over the edge of the countertop, you can purchase copper bars, 1/8 inch thickness is best, in different lengths and glue them to the edge. You still need to roll over the copper sheet and apply the copper bars over top of it. The seam should be soldered or brazed.
You can purchase a copper sink to finish the look or use a stainless steel or solid-surface material.