Installing A Transverse Expansion Joint In A Standing Seam Copper Sheetmetal Roof

Procedure code:
761002S
Source:
Hspg Prepared For Nps - Sero
Division:
Thermal and Moisture Protection
Section:
Sheet Metal Roofing
Last Modified:
10/23/2014


INSTALLING A TRANSVERSE EXPANSION JOINT IN A STANDING SEAM COPPER
SHEETMETAL ROOF


PART 1---GENERAL

1.01 SUMMARY

A. This procedure includes guidance on installing an
expansion joint in a standing seam copper sheetmetal roof
to prevent future sheetmetal cracking. GENERALLY, THIS
WORK SHOULD BE ACCOMPLISHED BY A EXPERIENCED ROOFING
CONTRACTOR.

B. Standing seam copper sheetmetal roofs sometimes crack in
long roof slopes (generally exceeding 30 feet). In roof
lengths greater than 30 feet, the sheetmetal bays are
unable to accommodate the cyclical stresses of expansion
and contraction over a long period of time. One way of
eliminating this problem is to install an expansion joint
across the roof slope to absorb some of the longitudinal
movement.

C. Long roof slopes of batten seam copper sheetmetal
typically do NOT experience this type of problem, as the
upstands in a batten roll system are separated by a wood-
roll which allow the individual bays to move
independently of one another.

D. Cracks caused by long roof slopes are usually
concentrated in the center of the roof area about 1/3 of
the way down the slope.

E. Safety Precautions:

1. Wear rubber-soled shoes that have non-slip or grid
type tread (preferably sneakers with a high top for
good ankle support). Avoid wearing loose clothing.

2. Wear a safety belt or harness and secure it to a
substantial chimney or to a window on the opposite
side of the building. Leave only enough slack so you
can work comfortably in one area, and adjust the
slack as you work on other sections of the roof.

3. Be sure the roof is clear of debris and water.

4. Do not work on wet or snow covered roofs. Work on
cleated walkboards.

5. Steep roofs: On roof slopes greater than 4 inches
rise per foot, special consideration must be given
to both footing and materials handling.

a. Secure chicken ladders or cleats at the top
for adequate footing.

b. Hang and secure approved safety lines with
rope of sufficient strength.

c. Carry a limited number of materials so that
balance and footing are not impaired.

d. Use scaffolding, ladders, and working
platforms as required to execute the work.
Ladders shall not be supported on hanging
gutters. The gutters may be distorted which can
affect the slope to drain.

F. Historic Structure Precautions: Historic and regional
roofing craftsmanship examples characteristic of the
structure are to be treated with sensitivity, to be
preserved and followed.

G. See 01100-07-S for general project guidelines to be
reviewed along with this procedure. These guidelines
cover the following sections:

1. Safety Precautions

2. Historic Structures Precautions

3. Submittals

4. Quality Assurance

5. Delivery, Storage and Handling

6. Project/Site Conditions

7. Sequencing and Scheduling

8. General Protection (Surface and Surrounding)

These guidelines should be reviewed prior to performing
this procedure and should be followed, when applicable,
along with recommendations from the Regional Historic
Preservation Officer (RHPO).

1.02 DEFINITIONS

A. anneal--the operation of heating and cooling the metal to
soften it and make it less brittle.

B. brazing--to solder with a non-ferrous metal that melts at
a lower temperature than that of the metals being joined.

C. bay--a unit of sheet covering as laid between rolls or
standing seams.

D. cleats or clips--copper strips, cut to lengths to suit
roll or seam, placed at intervals and securely fixed to
the roof base, the ends being welted in with the edges of
the sheets to hold the copper roofing in position.

E. cross welt or transverse seam--in flexible metal roofing,
a seam between sheets; usually parallel to the gutter or
to the ridge.

F. lock joint--a single or double welted joint.

G. solder--metal or metallic alloy of tin and lead used when
melted to join metallic surfaces.

H. standing seam--a double welted joint formed between the
sides of adjacent bays and left standing.

I. turn up--where the two adjacent edges of metal sheets are
brought together vertically and folded over.

J. welting--joining copper sheets at their edges by folding
together. Welting may have single or double folds, such
joints being termed single or double welts respectively.

1.03 SYSTEM DESCRIPTION

A. The maximum length of straight standing seam runs should
not exceed 30 feet. There should be no sign of strain at
the seams, especially at the cross welts.

1.04 QUALITY ASSURANCE

A. Qualifications: Copper roofing should be applied by
qualified sheet metal mechanics using methods devised or
approved by the manufacturer. Details may vary depending
on the properties of the metal, local custom, and
architectural effect required.

1.05 DELIVERY, STORAGE, AND HANDLING

A. Storage and Protection:

1. Keep uninstalled roof materials under cover, dry,
free from scratches, condensation, and distortion
during delivery, storage, and handling.

2. Salvage storage: Historic material to be used as
example of original construction shall be stored as
directed by the RHPO. Often original roof metal
scrap pieces with exposed weather can be found in
attic spaces.

3. Care must be taken to prevent damage to corners and
edges of metal roofing during handling and storage.

4. Manufacturer's delivery or job markings on metal,
and adhesives for manufacturer's labels shall be
either a neutral or slightly acidic material. In
no case shall such material be alkaline; any
staining of the metal by alkaline materials will
cause for the rejection of the piece.


PART 2---PRODUCTS

2.01 MATERIALS

A. Copper nails

B. Copper cleats

C. Copper sheet metal, weight to match existing (minimum 16
oz.)

D. Solder and flux

E. Cleaners

F. Rosin Paper

G. Lumber for cant strip

2.02 EQUIPMENT

A. Chicken ladder, safety belt or harness

B. Protective gloves and gear

C. Straight snips for cutting straight or slightly curved
lines in sheet metal 24 gauge or lighter

D. Soldering copper

E. Handy tongs for bending the edges of the solder

F. Metal seamer

G. The application of sheet-metal roofing requires a full
range of metal-working tools and shop equipment, plus
special handling, hoisting equipment, and machinery for
long lengths.


PART 3---EXECUTION

3.01 EXAMINATION

A. Whenever possible, make inspection from ground or from
above if possible.

B. Inspect for cracks near the cross seam of a long slope.

C. Inspect the underside of the roof deck from the attic to
detect leaks.

3.02 PREPARATION:

A. Surface Preparation:

1. Carefully examine, measure, and record existing
metal shingle or sheet metal patterns at edges,
hips, ridges, and other special conditions.

2. Be careful not to damage old metal wall and vent
flashings that may be used as a pattern for cutting
templates. If metal cap flashings at the chimney
and other vertical masonry wall intersections have
not deteriorated, bend them up out of the way so
that they may be used again.

3. For safety of the personnel, keep the deck clear of
waste material as the work proceeds.

4. For installation of new material, verify the type,
thickness, weight/gauge prior to installation.

3.03 ERECTION, INSTALLATION, APPLICATION

A. For a temporary repair where the number of cracks are
minimal, small copper patches may be soft-soldered over
cracks. For patching procedures, see 07610-05-R. Though
the patches will last for several years, it will
eventually be necessary to install an expansion joint
across the full slope of the roof to permanently reduce
thermal stresses.

B. Introducing a transverse expansion joint:

NOTE: For a detail of this procedure, see the book
Practical Building Conservation by John & Nicola Ashurst,
English Heritage Technical Handbook. Vol. 4: Metals.
New York: Halsted Press, 1988, p. 63.; check for latest edition of this book.

1. Make two cuts across the slope of the roof and
remove a section of roofing of sufficient width to
allow a wood cant strip to be nailed to the roof
deck.

2. The vertical height of the front of the cant strip
should be minimum of 1-3/8" with a gentle taper on
the uphill side of the slope of the roof.

3. Replace rosin paper as required where copper
roofing has been cut and the new copper will be
inserted.

4. Turn up the ends of the existing copper roofing
below the cant strip so that an upstand may be
formed to go against the front of the cant strip.

5. Anneal the seams on the existing copper roofing
above the cant strip for a distance of about one
foot, and carefully unfold the seams.

6. Along the full length of the new expansion joint
cut back alternate bays by 6" in order to create a
stagger in the final cross welts.

7. After a further anneal, fasten additional cleats or
clips into position as required.

8. Join new copper to the existing sheets with double-
lock cross welts.

9. Complete the standing seams and drip-edge welt.

3.04 PROTECTION

A. At the end of each work day, provide building protection
for any exterior roofing element removed for repair.


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