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Historic Preservation - Technical Procedures

Spectitle:

Repairing A Detached Standing Seam On A Copper Roof

Procedure code:

0761011R

Source:

Hspg Prepared For Nps - Sero

Division:

Thermal And Moisture Protection

Section:

Sheet Metal Roofing

Last Modified:

02/24/2012

Details:

Repairing A Detached Standing Seam On A Copper Roof



REPAIRING A DETACHED STANDING SEAM ON A COPPER ROOF


THIS PROCEDURE SHOULD ONLY BE PERFORMED BY AN EXPERIENCED
PROFESSIONAL AND ONLY UPON APPROVAL FROM THE REGIONAL HISTORIC
PRESERVATION OFFICER (RHPO).

THIS PROCEDURE SHOULD BE PERFORMED UNDER THE DIRECTION OF AN
HISTORICAL ARCHITECT OR ENGINEER TO DECIDE THE MOST EFFICIENT AND
LEAST DESTRUCTIVE MANNER FOR EXECUTING THE WORK.


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on repairing a detached
         standing seam on a copper roof.  GENERALLY, THIS WORK
         SHOULD BE ACCOMPLISHED BY AN EXPERIENCED ROOFING
         CONTRACTOR.  Though this technique applies specifically
         to copper roofing, the same principles are also
         applicable to other types of standing seam metal roofs.

    B.   Standing seams may become detached for several reasons:

         1.   If the fasteners securing the cleats have pulled
              out.  

              a.   This is especially true when copper tacks have
                   been used instead of the proper nails.  

              b.   Tacks are tapered throughout their length and,
                   therefore, even the slightest withdrawal will
                   seriously reduce their hold in the decking.  

              c.   The normal shrinkage of wooden deck members
                   due to natural drying out will aggravate the
                   situation.

         2.   If a seam has an insufficient number of cleats or
              some existing cleats coincide with joints or splits
              in the decking.  This, combined with localized high
              wind turbulence may cause individual seams to
              become detached.  

              a.   Cleats should be spaced at a maximum of 1'-3"
                   on center, and fastened to the deck by two
                   copper nails close to the turn up.  

              b.   Cleats spaced too far apart can break under
                   the repeated strain of wind loading.

    C.   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 before performing
         this procedure and should be followed, when applicable,
         along with recommendations from the RHPO.

1.02 DEFINITIONS

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

    B.   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.  

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

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

    E.   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.   A metal roof in good condition has not failed due to
         withdrawal of nails from the decking, nails have not
         pulled through the holes in clips, has sufficient clips
         provided in the seams, and that no breakage of clips has
         taken place.

1.04 PROJECT/SITE CONDITIONS

    A.   Environmental Requirements:

         1.   Wet weather:  Do not begin to repair metal roof in
              misty or rainy weather.  Do not apply metal roofing
              to wet roof sheathing.

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

1.05 MAINTENANCE

    A.   Wash copper metalwork at regular intervals to remove
         corrosive elements, especially areas which are not
         effectively washed by rainfall to remove dust, grime, and
         soot.  Carry out such cleaning with materials
         noncorrosive to copper or the copper patina.  

         NOTE:  AVOID CLEANING COPPER WITH ALKALINE SOAPS THAT DO
         NOT CONTAIN SODIUM HYDROXIDE, DETERGENTS CONTAINING
         PYROPHOSPHATES SUCH AS "TIDE" OR AMMONIA SOLUTIONS.
         THESE WILL ATTACK THE COPPER.

    B.   Clean the roof of dirt build-up annually by rinsing with
         clean, clear water.  

    C.   Keep the roof clear of debris, and trim all overhanging
         branches that might cause mechanical damage.

    D.   Inspect for and eliminate ant hills and/or bird droppings
         that can corrode sheet metals.

         1.   Bird droppings can cause localized corrosion on
              copper because of the acids found in the droppings.
         2.   Remove droppings using a wooden spatula; wash
              copper surface with a neutral detergent.

         3.   Rinse with distilled water and wipe dry with a
              clean soft cloth, to prevent water spots and
              streaks.

         CAUTION:  DO NOT USE BLEACH TO REMOVE BIRD EXCREMENT.
         BIRD DROPPINGS CONTAIN AMMONIA AND IF MIXED WITH BLEACH
         CAN FORM TOXIC GASES.

    E.   Inspect the secureness of cleats and fasteners and the
         condition of the sheet metal after particularly heavy
         storms.

    F.   Never use any black goop (asphaltic roofing compound) or
         caulk to seal joints on a metal roof.  Asphalt attacks
         metal roofing, and no caulk lasts long enough for this
         application.


PART 2---PRODUCTS

2.01 MATERIALS

    A.   Copper nails - large, flat head nails with barbed shank

    B.   Copper cleats

2.02 EQUIPMENT

    A.   Soldering iron to anneal edges of sheet metal
         (temperature of iron should not exceed 500 degrees)

    B.   Vise-Grip Crimpers, wood block and mallet, or metal
         seamer

    C.   Chicken ladder, safety belt or harness

    D.   Protective gloves and gear

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

    F.   Handy Tongs for bending the edges light sheet metal


PART 3---EXECUTION

3.01 EXAMINATION

    A.   Nails in the cleats that have withdrawn from the decking,
         may be unable to fall out of the cleat because they are
         covered by sheet metal.  As a result, they may turn on
         their side and prevent the seam from either resting on or
         being pressed flat against the top of the decking.

    B.   To decide if there are not enough cleats, note the
         positions of the cleat in the opened seam, and then
         closely examine the exterior of the other seams at
         approximately the same intervals in their length.  The
         additional thickness of the folded cleat frequently
         produces a slight bulge in the seam that is not too
         difficult to detect.

    C.   Poorly positioned fasteners, i.e., nails at the ends of
         the cleats instead of close to the turn up may allow a
         standing seam to be raised from the decking without the
         use of undue force.

3.02 ERECTION, INSTALLATION, APPLICATION

    A.   Using soldering iron, heat seam (anneal) as necessary to
         open it sufficiently to insert new cleats as required.

    B.   Fix new cleats at appropriate intervals and with proper
         fasteners, taking care to nail near the turn up.

    C.   Re-heat edges of sheet as required to make them workable.

    D.   Dress upstands together and fold over (welt) as required
         to finish seam.  Match existing appearance.

                             END OF SECTION