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Historic Preservation - Technical Procedures

Spectitle:

Minor Repairs To Slate Roofs

Procedure code:

0731501R

Source:

Hsr - Federal Bldg/P.O., Wash, Dc - Bldg Conservation Tech

Division:

Thermal And Moisture Protection

Section:

Slate Shingles

Last Modified:

05/28/2014

Details:

Minor Repairs To Slate Roofs



MINOR REPAIRS TO SLATE ROOFS


PART l---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on replacing individual
         cracked or broken slate shingles, and re-hanging loose
         shingles.  

         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

         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 REFERENCES

    A.  American Society for Testing and Materials (ASTM)
         www.astm.org 

1.03 SUBMITTALS

    A.   Samples:

         1.   Submit nails proposed for use to the RHPO for
              approval.

         2.   Submit slate shingles proposed for use to the RHPO
              for approval.

1.04 PROJECT/SITE CONDITIONS

    A.   Environmental Requirements:

         1.   Maintain the weathertightness of the roof during
              repair operations.

         2.   Protect adjacent shingles from damage during
              examination and repair of shingles.  DO NOT walk on
              slate shingles.


PART 2---PRODUCTS

2.01 MATERIALS

    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
              slates.

         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-
         corrosive.

    D.   Copper Sheeting:  Provide 16 ounce soft, rolled copper to
         match existing flashing (i.e. lead-coated copper,
         stainless steel, etc.)

2.02 EQUIPMENT

    A.   Slate cutter

    B.   Slate ripper

    C.   Slate hammer


PART 3---EXECUTION

3.01 EXAMINATION

    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
         writing.

    C.   Replacement of Slate Roofing (method one):

         1.   Slide in new slates to replace broken, missing or
              cracked slates.  Reuse existing full slates
              wherever possible.

         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
              other penetrations.

         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
         UNBEND.

         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.

3.03 ADJUSTING/CLEANING

    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
 


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