Technical Procedures Disclaimer
Prior to inclusion in GSA’s library of procedures, documents are reviewed by one or more qualified preservation specialists for general consistency with the Secretary of Interior Standards for rehabilitating historic buildings as understood at the time the procedure is added to the library. All specifications require project-specific editing and professional judgement regarding the applicability of a procedure to a particular building, project or location. References to products and suppliers are to serve as a general guideline and do not constitute a federal endorsement or determination that a product or method is the best or most current alternative, remains available, or is compliant with current environmental regulations and safety standards. The library of procedures is intended to serve as a resource, not a substitute, for specification development by a qualified preservation professional.
We’ve reviewed these procedures for general consistency with federal standards for rehabilitating historic buildings and provide them only as a reference. Specifications should only be applied under the guidance of a qualified preservation professional who can assess the applicability of a procedure to a particular building, project or location. References to products and suppliers serve as general guidelines and do not constitute a federal endorsement nor a determination that a product or method is the best alternative or compliant with current environmental regulations and safety standards.
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.
- 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.
- Standing seams may become detached for several reasons:
- If the fasteners securing the cleats have pulled out.
- This is especially true when copper tacks have been used instead of the proper nails.
- Tacks are tapered throughout their length and, therefore, even the slightest withdrawal will seriously reduce their hold in the decking.
- The normal shrinkage of wooden deck members due to natural drying out will aggravate the situation.
- 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.
- 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.
- Cleats spaced too far apart can break under the repeated strain of wind loading.
- If the fasteners securing the cleats have pulled out.
- See 01100-07-S for general project guidelines to be reviewed along with this procedure. These guidelines cover the following sections:
- Safety Precautions
- Historic Structures Precautions
- Quality Assurance
- Delivery, Storage and Handling
- Project/Site Conditions
- Sequencing and Scheduling
- 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.
- Anneal--operation of heating and cooling the metal to soften it and make it less brittle.
- 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.
- Standing seam--a double welted joint formed between the sides of adjacent bays and left standing.
- Turn up--where the two adjacent edges of metal sheets are brought together vertically and folded over.
- 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 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
- Environmental Requirements:
- Wet weather: Do not begin to repair metal roof in misty or rainy weather. Do not apply metal roofing to wet roof sheathing.
- At the end of each work day, provide building protection for any exterior roofing element removed for repair or replacement.
- 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.
- Clean the roof of dirt build-up annually by rinsing with clean, clear water.
- Keep the roof clear of debris, and trim all overhanging branches that might cause mechanical damage.
- Inspect for and eliminate bird droppings and other debris that can corrode sheet metals.
- Bird droppings can cause localized corrosion on copper because of the acids found in the droppings.
- Remove droppings using a wooden spatula; wash copper surface with a neutral detergent.
- 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.
- Inspect the secureness of cleats and fasteners and the condition of the sheet metal after particularly heavy storms.
- 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.
- Copper nails - large, flat head nails with barbed shank
- Copper cleats
- Soldering iron to anneal edges of sheet metal (temperature of iron should not exceed 500 degrees)
- Vise-Grip Crimpers, wood block and mallet, or metal seamer
- Chicken ladder, safety belt or harness
- Protective gloves and gear
- Straight snips for cutting straight or curved lines in sheet metal 24 gauge or lighter
- Handy Tongs for bending the edges light sheet metal
- 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.
- 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.
- 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
- Using soldering iron, heat seam (anneal) as necessary to open it sufficiently to insert new cleats as required.
- Fix new cleats at appropriate intervals and with proper fasteners, taking care to nail near the turn up.
- Re-heat edges of sheet as required to make them workable.
- Dress upstands together and fold over (welt) as required to finish seam. Match existing appearance.