Installing A Terne Sheetmetal Roof

Procedure code:
761007S
Source:
Hspg Prepared For Nps - Sero
Division:
Thermal and Moisture Protection
Section:
Sheet Metal Roofing
Last Modified:
03/13/2017

 

INSTALLING A TERNE SHEETMETAL ROOF

 

 

PART 1---GENERAL

1.01 SUMMARY

 

    A.   This procedure includes guidance in the application of

         four different types of seams for a terne sheetmetal

         roof.  For terne-coated stainless steel, see procedure

         07610-13-R.

 

    B.   In this procedure, it is assumed that the roof deck is

         wood, and that any insulation that may be required is

         installed within an attic space and allows for proper

         ventilation of the underside of the roof.  If conditions

         other than this exist, consult roofing material

         manufacturer.

 

    C.   For terne roofs, there are typically four types of seams

         used, depending on the appearance of the existing roof:

 

         1.   Flat seam (also called flat locked seam):  A seam

              between adjacent metal sheets, formed by turning up

              both edges, folding them over, and then flattening.

              In a flat seam roof, and at valleys, all seams are

              soldered.

 

         2.   Standing seam:  A seam between adjacent metal

              sheets, formed by turning up the edges of two

              adjacent sheets, and then folding them over.

 

         3.   Batten seam:  A seam that is formed around a wood,

              fiberglass or plastic core.  Typically, nearly

              square in cross-section.

 

         4.   Cross seam:  Cross seams are perpendicular to the

              above seams and are intended to provide the correct

              length for sheet metal pans.  They should be

              staggered from bay to bay to ensure strength and

              stability of the sheet metal.

 

    D.   Historic and regional roofing craftsmanship and details

         which are characteristic of the structure are to be

         treated with sensitivity.  Such details are to be

         preserved and copied.

 

    E.   Replacement roofing work shall be equal to original

         workmanship.  The appearance of the new roof shall match

         the existing roof in exposure, bay size, pattern and

         material.

 

    F.   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.   There should be no unnecessary walking over roof.

              The roof shall not be used as a storage area for

              other materials.

   

         3.   Wear a safety belt or harness and secure it to a

              substantial chimney or to a window on the opposite

              side of the house.  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.

 

         4.   Keep the deck clear of waste material as the work

              proceeds.  Sweep the deck clean after all old

              roofing has been removed.

 

         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

                    sufficient strength rope.

 

              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.

                   Scaffolding legs shall be planked to

                   distribute load to not exceed  20# per square

                   foot on roofs.  Ladders shall not be supported

                   on hanging gutters.  They may be distorted

                   which can affect the slope to drain.

 

    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.   Bay - a unit of sheet covering as laid between seams.  

 

    B.   Capping - a strip, covering the top of a batten roll,

         welted to the edges of the sheets which are dressed up

         the side of the roll.

 

    C.   Cleats or Clips - strips, cut to specified length

         according to the type of seam being used, placed at

         intervals directed by roofing manufacturer.  Cleats are

         securely nailed to the roof deck and the ends are welted

         in with the edges of the sheets to hold the roofing

         sheets in position.

 

    D.   Drip edge - formed metal sheets at roof edges which

         prevent water from dripping down vertical surfaces.  One

         edge is welted to roof sheeting to form weather-tight

         seam.

 

    E.   Expansion cleats - additional cleats which accommodate

         the thermal movement of the metal covering when a single

         length of metal exceeds 30'.

 

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

 

    G.   Saddle End - the completion of a batten roll covering or

         a standing seam against an abutment.

 

    H.   Solder - metal or metallic alloy of tin and lead used to

         join metallic surfaces.

 

    I.   Standing Seam - a double welted joint formed between the

         sides of adjacent bays and left standing.

 

    J.   Welting - joining metal sheets at their edges by folding

         together.  Welting may by single or double folds, such

         joints being termed single or double welts respectively.

 

1.03 SUBMITTALS

 

    A.   Shop Drawings:  Before replacing roofing, prepare

         working drawings showing bay width and length between

         seams.  Prepare typical and unusual seam details, valley

         details, and fastening patterns for reroofing guidance.

 

1.04 PROJECT/SITE CONDITIONS

 

    A.   Wet weather:  Do not apply new metal roof in misty or

         rainy weather.  Do not apply metal roofing to wet roof

         sheathing.

 

    B.   Terne metal is likely to deteriorate from chemical action

         by pitting or streaking.  This can be caused by airborne

         pollutants; acid rainwater; acids from lichen or moss;

         uncured alkalis found in lime mortars or portland cement

         fastenings.

 

 

PART 2---PRODUCTS

2.01 MANUFACTURERS

 

    A.  Revere

         www.revere.com

         Follansbee, WV  26037

         

 

    B.   Metal Sales Mfg. Corp.

         www.metalsales.us.com

         

         

    2.02 MATERIALS

 

    A.   Fasteners:

 

         1.   Nails - 7/8" minimum length, flat head, galvanized

              roofing nails

 

         2.   Screws - For batten seam roofs, use galvanized

              screws, long enough to securely fasten batten to

              roof deck.

 

    B.   Terne cleats - 2" wide, length as required by type of

         seam being used.  Consult roofing manufacturer.  Pre-

         formed cleats are often available.

 

    C.   Terne sheetmetal - to match gauge, or .012 (30 ga.) or

         .015 (28 ga.) as directed by roofing manufacturer based

         on type of application; see 3.02 below.

 

    D.   Solder - 50% tin, 50% lead

 

    E.   Rosin soldering flux

   

    F.   Rosin Paper

 

    G.   Paint - red iron oxide, linseed oil; especially

         formulated to be used on terne metal

 

    H.   Wood, fiberglass or metal battens - size dictated by

         existing roof.

 

2.03 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

 

    D.   Soldering copper, soldering iron

 

    E.   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 PREPARATION

 

    A.   Surface Preparation:

 

         1.   Prior to installation, remove all oil, dirt, and

              other debris from the roof deck.  All surfaces

              shall be dry and free from frost.

 

         1.   Carefully examine, measure, and record existing

              sheetmetal 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.  Be especially careful

              roofing in these areas to avoid damaging reusable

              base flashing.  

 

         3.   Inspect the deck to determine whether it is sound.

 

              a.   Remove loose or protruding nails or hammer

                   them down.  

 

              b.   Replace rotted, damaged, or warped sheathing

                   or delaminated plywood.  DO NOT USED WOOD

                   TREATMENTS WHICH ARE HYGROSCOPIC OR CHEMICALLY

                   TREATED.  Spacing between boards shall be no

                   more than 2".  Plywood shall have a minimum

                   thickness of 1/2".

 

         4.   Make whatever repairs are necessary to the existing

              roof framing to strengthen it and to level and true

              the deck.

 

         5.   Lay rosin paper over the deck.  DO NOT secure to

              deck.  This paper serves as a slip sheet between

              the terne metal and the deck.  DO NOT use roofing

              felt as an underlayment on a terne roof.

 

3.02 ERECTION, INSTALLATION, APPLICATION

 

    A.   Flat Seam Applications:

 

         1.   Terne shall be .012 (30 ga.) or .015 (28 ga.).

              Terne is available in 14" x 20" and 20" x 28"

              sheets.  Maximum sheet size is 20" x 28".

 

         2.   Form sheets on a brake as indicated by roofing

              manufacturer.  

 

              a.   Mark folds 3/4" from edge on all four edges.

                   Clip corners at 45 degree angle at intersections of

                   markings.  

 

              b.   Fold two adjacent edges up and over and the

                   opposite adjacent edges down and under the

                   sheet.

 

         3.   After all sheets have been prepared in this manner,

              paint one side of each sheet with one coat of

              primer made for terne metal.  THE MILL-APPLIED SHOP

              COAT IS NOT SUFFICIENT.  Allow to fully dry before

              proceeding.  All special pieces such as drip pans

              shall also be painted in this manner.

 

         4.   Before beginning the first course, be governed by

              proper application at ridge, drip edge, end or side

              wall, gutters, valleys, etc.  Consult roofing

              manufacturer.  All roof perimeters shall have

              appropriate terne metal drip edge.

 

         5.   Place first sheet, paint side down, into position

              at the lowest point of roof slope.  Top edge must

              be one of the edges which is folded up and over.

              Hook one end of cleat into edge formed on sheet and

              nail free end of cleat to deck.  Place nail close

              to the fold but DO NOT NAIL THROUGH ROOFING SHEET.

              Bend end of cleat up and over nail head.  Attach

              each sheet with two cleats per side.

 

         6.   Continue laying roofing sheets in this manner.

              Align horizontal joints, stagger all vertical

              joints.  Lay individual sheets so that the fold of

              the sheet higher on the roof hooks onto and is over

              the fold of the lower adjoining pan.

 

         7.   At valleys, edges of individual roofing sheets will

              require custom fitting to provide proper flat lock

              seam.  Sheet metal used for valleys should be as

              long as possible to reduce the number of cross

              seams.

 

         8.   All seams must be soldered.  Use solder that is 50%

              tin and 50% lead only.  Use rosin only as a flux.

              Remove excess rosin before painting.  

 

              NOTE:  FLUX CONTAINING ANY ACID SHALL NOT BE USED.

 

         9.   Surface must be painted as soon as possible after

              completion of roof.  Paint as directed below in D.

 

    B.   Standing Seam Application, 3" per foot minimum pitch (for

         lower slopes consult roofing manufacturer):

 

         1.   If initial sheet width is 20" wide or less, terne

              shall be 30 ga.  If initial sheet width is greater

              than 20" use 28 ga.

 

         2.   Determine width and length of each pan.  Maximum

              recommended width between seams is 21", with

              maximum length of 20'.  If pan length is between

              20' and 30', pan width between seams should be

              reduced to 17".  Final pan width should match

              original roof.  Individual pans may be either

              preformed by the manufacturer or formed on site.

   

              a.   Taper pans longitudinally (narrower at the

                   bottom) a minimum 1/16" to fit at the cross

                   seams.

 

              b.   To form on site, fold one long side up 1-

                   15/32", forming a 90 degree angle.  Fold top 15/32"

                   over 90 degrees to create a "C" in section.  The

                   folded piece is called an up-stand.

 

              c.   Fold opposite long side up 1-7/8", forming a

                   90 degree angle.  Fold top 7/8" over 90 degrees away from

                   the pan.  Fold 3/8" of top edge down so that

                   it is parallel with the 1" up-stand.

 

              d.   To form fold for cross seam at both the top

                   and bottom of the pan make a 3/4" long cut

                   parallel to the up-stand and 1" away from the

                   up-stand.  At the top end of the pan, make a

                   fold up and over.  At the bottom of the pan,

                   make the fold up and back behind.

 

         3.   IF TERNE DOES NOT ALREADY HAVE A MILL-APPLIED SHOP

              COAT, UNDERSIDE OF ALL PANS MUST BE GIVEN ONE COAT

              OF TERNE METAL PRIMER.  Primer should be brush

              applied and allowed to dry thoroughly before

              installation.

 

         4.   Lay down first pan, paint side down, into position.

              Hook one end of cleat into side of pan whose

              up-stand has only two folds.  Nail free end of cleat

              to deck using two nails.  Place nails close to the

              up-stand but DO NOT NAIL THROUGH PAN.  Bend end of

              cleat up and over nail heads.  Cleats should be

              spaced approximately 12" on center, the entire

              length of the pan.

 

         5.   Where cross seams are required:

 

              a.   on roofs with pitch greater than 6" per foot,

                   slide two cleats onto fold at top of pan.

                   Place each one about 1" away from the up-stand.

                   Nail as described under A.5. above.  Hook next

                   higher pan over fold and cleat of lower pan

                   and carefully mallet seam together.

 

              b.   on roofs with pitch less than 6" per foot,

                   cleats secure lower pan as described above.

                   Approximately 4" below the fold of pan solder

                   a strip of terne, approximately 1-1/2" wide by

                   the full width of the pan.  Use solder that is

                   50% tin and 50% lead only.  Use rosin only as

                   a flux.  Remove excess rosin before painting.

                   Solder only the upper edge of the strip in

                   place.  The bottom fold of the next upper pan

                   hooks onto this strip rather than the fold of

                   the pan which has been folded in with the

                   cleat.  The upper pan will then cover both the

                   fold and cleat of the lower pan, and the

                   strip.

 

         6.   With first row of pans secure, lay second row next

              to the first row, leaving a 1/16" gap between the

              up-stands.  Fold up-stands of two pans together and

              down creating a 1" tall standing seam.  Continue in

              this manner until roof is covered.  Stagger cross

              seams in a uniform pattern.

 

         7.   At valleys, drip edges and other special

              conditions, sides of pans will require custom

              fitting to provide proper seams.  Consult

              manufacturer for difficult situations.  Sheet metal

              used for valleys should be as long as possible to

              reduce the number of cross seams.

 

         8.   To form the ridge, the top of last pan on one slope

              should extend beyond the ridge the desired height

              of the ridge seam, plus 1/2".  The last pan on the

              other slope should extend the desired height of the

              ridge seam plus 3/4".  Make a 180 degrees fold in each pan

              so that the folds on both slopes butt against each

              other.  Approximately 3" before the ridge, fold all

              standing seams flat, facing in the same direction.

              Fold the top 1/4" of the higher of the ridge

              stand up over the shorter ridge.  Fold both

              ridge up-stands over a minimum of 1/2" and press

              together.

 

         9.   Standing seams and cross seams need NOT be

              soldered.  Seams at valleys, however, MUST be

              soldered.  Use solder that is 50% tin and 50% lead

              only.  Use rosin only as a flux.  Remove excess

              rosin before painting.  

 

              NOTE:  FLUX CONTAINING ANY ACID SHALL NOT BE USED.

 

         10.  Surface must be painted as soon as possible after

              completion of roof as directed in section D. below.

 

    C.   Batten Seam Application for application of 3" per foot

         minimum pitch  (Consult roofing manufacturer if roof

         pitch is less than 3" per foot):

 

         1.   If initial sheet width is 20" wide or less, terne

              shall be 30 ga.  If initial sheet width is greater

              than 20" use 28 ga.

 

         2.   Determine width and length of each pan.  Maximum

              recommended width between seams is 21".  Final pan

              width should match original roof.  Maximum length

              of each pan in 10'.  Individual pans to be formed

              on site.  

 

              a.   Taper pans longitudinally (narrower at the

                   bottom) a minimum 1/16" to fit at the cross

                   seams.

 

              b.   Folds required for this type of seam are

                   complicated.  Form sheets on a brake as

                   indicated by roofing manufacturer.

 

         3.   IF TERNE DOES NOT ALREADY HAVE A MILL-APPLIED SHOP

              COAT, UNDERSIDE OF ALL PANS MUST BE GIVEN ONE COAT

              OF TERNE METAL PRIMER.  Primer should be brush

              applied and allowed to dry thoroughly before

              installation.

 

         4.   Lay down battens which have been sized to match

              original roof.  Screw battens to roof deck,

              matching center lines of original battens.

 

         5.   Nail cleats to vertical sides of battens, two nails

              per cleat.  Space cleats 12" on center the length

              of each batten, placing cleats opposite on another.

              Cleats shall extend 1" above the top of each

              batten.

 

         6.   At valleys, drip edges and other special

              conditions, sides of pans will require custom

              fitting to provide proper seams.  Consult

              manufacturer for difficult situations.  Sheet metal

              used for valleys should be as long as possible to

              reduce the number of cross seams.

 

         7.   Lay individual pans as directed by manufacturer.

              Allow 1/16" space between vertical side of pan and

              the batten.  Fold seams as directed.

 

         8.   Form cross seams as directed above in 3.02.B.5.

 

         9.   Surface must be painted as soon as possible after

              completion of roof as directed in section D. below.

 

    D.   Painting terne roof after completion of installation.

 

         1.   All surfaces must be clean and dry.  DO NOT PAINT

              OVER CONDENSATION.

 

         2.   Painting shall be done on a warm, dry day, when

              both the roof surface and air temperature is

              approximately 50 degrees F.

 

         3.   Apply one coat of primer made especially for terne.

              MILL APPLIED SHOP-COAT SHALL NOT BE CONSIDERED A

              SUBSTITUTE FOR PRIME COAT.  Paint shall be brushed

              on to allow oil to adequately penetrate and adhere

              to metal.  Allow to dry before applying finish

              coat.

 

         4.   Apply one top coat, using finish paint which has

              been made to be used with selected primer.  Top

              coat shall be brush applied.

 

    E.   Roof Maintenance:

 

         1.   Whenever possible, make inspection from ground or

              from above if possible.

 

         2.   Inspect ridge details and eaves for metal

              punctures, and broken joints or seams.  Inspect for

              rust, excessive weathering or exposure, erosion, or

              staining indicating overall deterioration.

 

         3.   Inspect the underside of the roof deck from the

              attic to detect leaks.  Flashings are the most

              vulnerable points.  Therefore, inspect the

              underside carefully at all flashing points for

              evidence of leakage such as water stains.

 

         4.   In addition to scheduled inspections, inspect after

              each exposure to unusually severe weather

              conditions such as strong winds, hail, or long

              continuous rains.

 

         5.   Rinse dirt with water annually.

 

         6.   Keep the roof clear of debris, and trim all

              overhanging branches that might cause mechanical

              damage.

 

         7.   Inspect for and eliminate bird

              droppings and any other debris which can corrode sheet metals.

 

         8.   Inspect the secure-ness of cleats and fasteners and

              the condition of the sheet metal after particularly

              heavy storms.

 

                             END OF SECTION

 

Last Reviewed 2017-03-13