7.2. Joints and Seams

Rigid Seams

7.2A. Lap Seam, Soldered

This seam should only be used on copper sheets with weights up to 20 ounces.

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7.2B. Flat Lock Seam, Soldered

This seam provides a positive mechanical connection between adjacent sheets. It should not be used for copper sheets weighing more than 20 ounces per square foot. It should be used where watertightness is required.

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7.2C. Lap Seam, Riveted

This seam provides a strong mechanical connection for copper sheets. It should only be used where watertightness is not required.

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Where strength of seam is a major consideration, rivets should be copper or copper alloy, 1/8" to 3/16" in diameter and spaced 3" O.C. in two rows in a staggered pattern. The use of 1/8" pop rivets of either copper or copper alloy should be restricted to applications where strength of seam is not a major consideration.

7.2D. Single Lock Standing Seam, Button Punched

This is one type of standing seam. Both copper sheets are bent up where they meet. One is longer than the other. The longer one is folded over the shorter one. They are then button punched to provide a more rigid, mechanical connection.

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7.2E. Lap Seam Riveted and Soldered

This seam offers a strong, watertight joint.  The rivets provide strength, while the solder provides a watertight seal.

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Loose Seams

This type of seam allows thermal expansion and contraction by sliding or flexing. It can be made watertight by the use of high quality flexible sealants, such as butyl, polysulfide, silicone, or urethane, which do not restrict movement.

7.2F. Lap Seam

This seam is not used where water-tightness is required. It allows free movement of the copper sheets.

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7.2G. Flat Lock Seam, Cleated

The cleats are used to secure the sheets to the understructure. Cleats should (in general) be spaced a maximum of 12" O.C.

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7.2H. Double Lock Seam, Cleated

This seam is essentially a single lock seam with an additional fold. It develops increased mechanical strength and watertightness.

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7.2I. Common Lock

(also referred to as a hook seam or single lock seam) This seam provides for a mechanical connection between the copper sheets. The hook in the lower sheet provides a degree of security against water penetration as long as it is not submerged. It also provides a good place for sealant when used.

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Expansion Seams

This type of seam is used wherever significant movement of the copper sheets is expected. Expansion and contraction are a function of temperature change, material properties, and the dimensions of the material. The amount of movement can be calculated with the following general formula:

dL = L x E x dT

Where:

dL = change in length (expansion or contraction)

L = Length of copper material

E = coefficient of linear expansion of copper = 0.0000098 per degree Fahrenheit

dT = temperature change in degrees Fahrenheit

Calculation of movement is rarely required in short roof pan construction, since the details shown here can accommodate thermal movement of short pans.

7.2J. Clevis Seam

This seam is similar to the slip expansion seam. The difference is in forming the lock. Where as the slip expansion lock is formed by braking a sheet of copper, the lock on this seam is formed by soldering a small strip of copper below the sheet.

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7.2K. Slip Expansion Seam

The tail piece of the formed lock section may be nailed to secure it more firmly to the substrate. The joint is filled with sealant for watertightness.

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7.2L. Loose Lock With Sealant

This expansion seam is formed by filling a loose lock seam with a non-hardening, elastic sealant. The space between locks is required to allow for expansion and contraction.

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Corner Seams & Edges

7.2M. Edge Strip

Two edge strips are shown. Edge strips are used for securing copper roofing at eaves, gable ends, etc. The edge strip shown in Detail 1 is attached to the fascia board with nails at 3" O.C. The locking strip is turned out 45 degrees a minimum of 3/4".

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The horizontal flange in Detail 2 projects back onto the roof a maximum of 4". It is secured with copper or copper alloy nails spaced 3" apart. The locking member is hemmed for at least 3/4".

7.2N. Hemmed and Brake Formed Edge

These are used as edge stifferes at free edge.

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7.2O. Double Seam Corner Lock

This detail is preferred over the single seam corner lock because the folds provide a more secure edge. It should be used if the copper fascia is part of an overhang detail.

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7.2P. Single Seam Corner Lock

The end of the copper sheet is locked over the edge strip in a 3/4" lock.

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