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Historic Preservation - Technical Procedures
Minor Repairs To Slate Roofs
Hsr - Federal Bldg/P.O., Wash, Dc - Bldg Conservation Tech
Thermal And Moisture Protection
Minor Repairs To Slate Roofs
MINOR REPAIRS TO SLATE ROOFS
A. This procedure includes guidance on replacing individual
cracked or broken slate shingles, and re-hanging loose
NOTE: THIS WORK SHOULD BE PERFORMED BY AN EXPERIENCED
ROOFING CONTRACTOR WITH EXPERTISE IN WORKING WITH SLATE.
B. If 20% of roof requires repair, complete replacement
should be considered.
C. See also procedure 07315-02-S for general information
concerning slate. See 07315-04-S for supplemental
guidelines for repairing and replacing slate roofs.
D. 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
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).
A. American Society for Testing and Materials (ASTM), 100
Barr Drive, West Conshohocken, PA 19428, (610) 832-9585
or FAX (610) 832-9555.
1. Submit nails proposed for use to the RHPO for
2. Submit slate shingles proposed for use to the RHPO
1.04 PROJECT/SITE CONDITIONS
A. Environmental Requirements:
1. Maintain the weathertightness of the roof during
2. Protect adjacent shingles from damage during
examination and repair of shingles. DO NOT walk on
A. Slate Shingles:
1. Provide new slate shingles hand-cleft from sound
stone, meeting Federal Specification, 55-5-451,
Grade A, maximum water absorption (ASTM C121) of
.1%. Color and appearance shall match existing as
closely as possible.
2. Thickness: 3/16 inch nominal thickness, or to
match existing; thickness to be within the
tolerances of minus 0 inches and plus 1/8 inch.
3. Shingle Size: To match existing.
B. Nails: Provide large head hard copper wire nails
1. Wood deck: (Length of nail equals twice the
thickness of the slate plus 1".) 3d nails for
standard slates up to 18 inches long; 4d nails for
extra long slates; 6d nails for ridge and hip
2. Concrete Deck: 1-1/2 inch length, 10 gauge
suitable for driving into nailing concrete.
C. Roofer's Cement: ASTM D-282. Non-staining and non-
D. Copper Sheeting: Provide 16 ounce soft, rolled copper to
match existing flashing (i.e. lead-coated copper,
stainless steel, etc.)
A. Slate cutter
B. Slate ripper
C. Slate hammer
A. Inspect the conditions under which the work is to be
carried out. Inspect the condition of the roof deck to
which the slate shingles will be applied. Report any
unsatisfactory conditions to the RHPO. DO NOT walk on
slates during examination.
3.02 ERECTION, INSTALLATION, APPLICATION
A. Removal of Existing Loose or Damaged Shingles:
1. Using a slate ripper, carefully remove any loose,
cracked and broken slate shingles from the roof,
taking care not to break those that are only loose.
Remove any remaining small pieces of slate.
2. Store removed full slate shingles for reuse, to the
extent desired by the Contracting Officer on the
job site where directed.
B. Acceptance of Roof Deck: Inspect roof deck for flaws
which could prevent the proper installation of the new
slates. Report any defects to the Contracting Officer in
C. Replacement of Slate Roofing (method one):
1. Slide in new slates to replace broken, missing or
cracked slates. Reuse existing full slates
2. Line up slate in its course making sure any pre-
punched holes are covered by the slates above.
3. Neatly fit the slate around all pipes, vents and
4. Mark location of new nail hole through the vertical
joint of slates in the overlying course,
approximately 5 inches from the head of the
overlaying slate or 2 inches below the tail of the
second course of slate above.
5. Punch or drill new hole and nail slate into
position using copper nails as specified. Cut nail
head as required to fit between slates in
overlaying courses. Nail shall not be driven so
far as to put strain on the slates; slate should
hang from the nail.
6. Slates overlapping sheet metal shall have the nails
so placed as to avoid puncturing the sheet metal.
7. Cut a piece of copper approximately 3 inches wide
by 8 inches long. Cut edge slightly to help with
friction fit. Bend piece slightly lengthwise to
make it concave or convex which will insure its
remaining tightly in place. Insert the piece of
copper lengthwise over the slating nail and under
the course above so that it extends a approximately
two inches under the succeeding course and
completely covers the new nail hole.
D. Alternative method: THIS METHOD SHOULD NOT BE USED IN
NORTHERN CLIMATES WHERE SNOW AND ICE COULD CAUSE TAB TO
1. Remove damaged slate as directed above.
2. Cut a copper tab approximately 1 inch wide by 8
inches long. Double over bottom 4 inches and bend
up to form an "L" shape.
3. Nail top of tab to roof deck using a copper nail.
Daub nail head with non-corrosive, non-staining
elastic roofing cement.
4. Slide replacement slate into place so that bottom
of slate rests on copper tab. Bend doubled portion
of tab up and over the bottom of the slate to hold
it in place. Approximately 1 inch of the tab
should be visible.
A. Clean work areas of all debris as roofing work
progresses. At conclusion of job, clean up loose slates,
containers and nails and leave job site neat and clean.
END OF SECTION