Removing And Replacing Built-Up Roofing Using Cold-Applied Mastics
- CSI Division:
- Division 7 - Thermal and Moisture Protection
- Cold Applied Bituminous Roofing
- Last Modified:
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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.
A. This procedure provides guidance on removing and installing a cold process built-up roof. This includes work for the following:
- Removing an existing built-up roof, insulation, cants and flashings to the deck or substrate.
- Priming concrete decks where applicable.
- Loose laying vapor barrier on new metal decks where applicable.
- Installing cricketing and field-tapered insulation as required, except where no rigid insulation is to be installed.
- As applicable, mechanically fastening new insulation at metal decks, or priming deck and hot mopping at concrete deck areas.
- Installing specified cold process roof system over substrate as required.
- Installing pitch pockets as required.
- Installing sheet lead at all drains (4 lb. lead typical).
- Installing new lead vent stack flashings (materials furnished by others but installed herein).
- Installing base flashings at all walls and equipment bases.
- Installing a surface mounted reglet flashing as required.
B. 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 prior to performing this procedure and should be followed, when applicable, along with recommendations from the Regional Historic Preservation Officer (RHPO).
A. Cold-process membrane assembly shall be evaluated under the following applicable standards of the American Society for Testing and Materials (ASTM), 100 Barr Drive, West Conshohocken, PA 19428, 610-832-9585 or FAX 610-832-9555.
- 1. ASTM D2523 load-strain properties of roofing membranes.
1.03 SYSTEM DESCRIPTION
A. Roof surfaces shall be sound, clean and dry, reasonably smooth and free from loose and foreign material and from depressions that would interfere with proper drainage.
A. Product Data: Prior to the application of any roofing materials, the roofing contractor shall submit to the Government the materials manufacturer's literature and descriptive information applying to the materials proposed for this project. A letter shall be furnished from the material manufacturer indicating that all materials used on this project conform to their respective ASTM specification. A conformation letter from a supplier will NOT be acceptable. Under no circumstances shall the contractor start work prior to material approval.
1.05 QUALITY ASSURANCE
- The roofing contractor shall be certified bondable or guaranteeable by the roofing manufacturer. The applicators shall have at least three years experience in applying the specified system.
- Applicator shall be qualified under the manufacturer's guaranteed roof systems program.
- Manufacturer Representative's Responsibilities shall be:
- Rendering any inspection services the RHPO or designated representative may request.
- Calling to the attention of the contractor those matters observed which he considers to be in violation of the contract requirements.
- Reporting to the RHPO or designated representative in writing any failure or refusal of the contractor to correct unacceptable practices called to his attention.
- Confirming, after completion of the work and based on his observations and test, that he has observed no application and procedures in conflict with the specifications, other than those that may have been previously reported. Final payment will not be released until this confirmation has been received by the RHPO.
- The presence and activities of the material manufacturer's field representative shall in no way relieve the contractor of his contractual responsibilities. In the event of a dispute, the RHPO or designated representative shall have final authority.
- Bidders are required to visit the site to ascertain the local conditions readily determined by field inspection and inquire such as location, contractor's access area, general character of the site, and compare the plans and specifications with the field conditions. Failure to visit the site will in no way relieve the contractor from furnishing any materials or performing any work required to complete the project in accordance with the specifications without any additional cost to the Federal Government.
B. Regulatory Requirements: Comply with fire, safety and environmental protection regulations.
C. Pre-installation Conference: A preconstruction conference will be held at which time the contractor will be given notice to proceed. At this time the contractor shall submit all literature and samples required throughout the specifications for the installation of the vapor retarder, roof insulation, and roofing system. The contractor and the job site superintendent shall attend the meeting.
1.06 DELIVERY, STORAGE AND HANDLING
A. Packing and Shipping:
- Deliver material in manufacturer's original, unopened containers with manufacturer's labels intact and legible.
- Deliver enough material to allow continuous work.
Acceptance at Site: Immediately remove and dispose of wet materials.
Storage and Protection:
- Store rolls of felt, cartons of asphalt and cans and drums of cements, primers and coatings on end.
- Store materials on clean, raised platforms.
- Store and handle materials to protect them from:
- Moisture, whether due to rain, snow or condensation.
- Damage by construction traffic.
- Direct sunlight.
- Mud, dust, sand, oil, grease and dirt.
- Select and operate material handling equipment and store materials to keep from damaging existing construction or applied roofing.
1.07 PROJECT/SITE CONDITIONS
A. Environmental requirements:
- Apply all roofing in dry weather.
- Do not apply roofing when ambient temperature is below 40 degrees F. or when wind speed is over 30 mph.
- Avoid heavy traffic on the work during all phases of installation.
- Replace or restore to original condition any materials or work damaged during construction.
- Protect paving and building walls adjacent to hoists, kettles and dumpsters.
- Lap protective material at least 6".
- Vent plastic sheets, if used, to keep moisture from condensing and collecting on covered surfaces.
- Secure protective coverings against wind.
- Leave protective covering in place until roofing work is complete.
- Protect existing rooftop equipment against dust and debris entry. Coordinate shutdown with RHPO.
A. Work as specified under this specification shall be covered under the manufacturer's five (5) year guarantee program.
3735 Green Road
Beachwood, OH 44122
A. General: Roofing components including, but not limited to, cold process adhesives, elastomeric flashings, reinforcement fabrics, felts, and mats, mastics, and sealants shall originate from single-source manufacturer consistent with the manufacturer's warranty requirements. Roofing ply sheets, rigid insulation, cover board, and roofing asphalt (for required hot mopping) meeting criteria specified herein may originate from any source.
B. Asbestos: Products containing asbestos are prohibited on the project. All roofing materials shall be completely asbestos-free.
C. Cold process roof system materials that may be incorporated in the work include, but are not limited to the following:
- Tremco Burmastic Adhesive, or approved equal.
- Tremco Tremlastic, or approved equal.
- Tremco Double Duty Aluminum, or approved equal.
- Tremco ELS Mastic, or approved equal.
- Tremco Polyroof Elastomer, or approved equal.
- Tremco 6" Burmesh, or approved equal.
- Reglet Joint Sealant, as approved by system manufacturer.
- Tremco TremPrime Q.D. Roof Primer, or approved equal.
- Tremco Tremply Hypalon Base Flashing, or approved equal.
- Tremco Sheeting Bond, or approved equal.
- Traffic Topping: Rubberized material approved by system manufacturer for heavy foot traffic.
- Non-Shrink Grout, as approved by system manufacturer.
- Reglet Primer, as approved by system manufacturer.
- Reglet Cleaner, as approved by system manufacturer.
- Sealant Tape, as approved by system manufacturer.
D. Ply Felts
- Buildex Roofgrip with 3" plate
- Dekfast with 3" plate
- Fabco with 3" plate
F. Vapor Retarder for New Metal Decking: Laminated foil scrim, poly sheet with a maximum flame spread rating of 5 (both surfaces) by U.L. classification. Perm rating shall be .02 or less. Provide accessory tape with same flame spread for joints.
G. Thermal Insulation: Polyisocyanurate Foam Board Insulation: Rigid boards of minimum 2.0 lb./cu. ft. density polyisocyanurate based foam core, permanently bonded to roofing felt facer sheets. Provide in 3" thickness, with minimum aged K-value of 0.17.
H. Cover Board: 1/2" thick six-side asphalt coated fiber board.
I. Cants: Fiber type, 3" minimum vertical rise.
J. Cricketing Material: Perlite Board Roof Insulation: Rigid, noncombustible, perlite/fiber boards of thicknesses indicated, with k-value of 0.36 at 75 degrees F. (24 degrees C.), integrally skinned surfaces, complying with ASTM C 728. Provide in manufacturer's standard sizes. Note: at contractor option, factory tapered perlite board may be furnished.
K. Coating at Existing Sheet Metal Roofs:
- Tremco Tremlastic, or approved equal.
- Primer: as approved by manufacturer for coating and substrate.
A. Protection: A skilled, experienced foreman will be on the job at all times during the installation of the roofing.
- The roofing contractor shall remove the existing roofing through the use of enclosed trash chutes or large bucket type containers. No debris or trash shall be thrown from the roof edge. Any damage resulting to exterior walls as result of the roofing operation shall be fully repaired to the satisfaction of the Government Representative.
- The contractor shall NOT remove more roofing than can be adequately covered and waterproofed on the same day. It is the contractors responsibility to keep the roof in a waterproof condition at all times throughout the life of this contract.
- The contractor shall NOT pile or store debris on the roof surface. All removed roofing shall be discarded on a daily basis.
- Every precaution shall be taken to keep moisture out of the roofing during its application. Felts, insulation and gravel shall be completely dry when laid. No part of the roofing materials shall be applied or laid during damp or rainy weather, or while moisture of any kind is present in visible amounts on the surface to be covered. Roof insulation or roofing felts that become wet from any cause during the progress of the work shall be removed from the job site in its entirety.
B. Surface Preparation:
- Apply temporary waterstops consisting of two plies of felts and moppings of asphalt at the end of each days work over the exposed edges of insulation and felts.
- Remove these temporary measures prior to the resumption of any additional work.
- The contractor shall notify the Contracting Officer seven working days before any demolition on roofing work is started. Roofing shall not be placed until such work has been inspected and permission given by the Government Representative. The Government Representative shall inspect all roofing as it is applied.
3.02 ERECTION, INSTALLATION, APPLICATION
NOTE: ROOFING TO BE LAID IN STRICT ACCORDANCE WITH MANUFACTURER'S CURRENT PUBLISHED SPECIFICATIONS FOR ROOF DECKING MATERIALS INDICATED, AND ROOF DECK MUST BE DRY, SMOOTH AND CLEAN.
A. Phased application of the roofing materials (layer by layer, over several days) SHALL NOT BE DONE. Work only on an area which can be completely roofed (up to protective coating) in a single working day. At edges of new work, each successive layer shall leave some of the previous layer exposed for covering the next day. Before the next day's work is begun, all dust, debris, bird droppings and moisture which has accumulated during the night shall be completely removed from the exposed edges before new material is added.
B. Tear Off and Removal:
- Progressively remove the existing built-up roof membrane and insulation down to the deck by the use of hand tools or other means approved by authorities having jurisdiction for removal of existing materials containing asbestos fibers. Verify and comply with requirements imposed by regulatory agencies. Transfer all debris off site to an appropriate landfill. Pay all landfill charges.
- Similarly remove base flashings from all perimeter vertical surfaces. Leave all such surfaces sufficiently smooth to receive new base flashings, fully and adequately bonded. DO NOT use sandblasting or other abrasive means to remove remaining residue.
- Where indicated to remain unreplaced, remove and clean all drainage fittings, clamp rings, sumps and etc., on drains and store for later reinstallation. Plug drains to prevent debris entry. Discard old lead.
- Where necessary for proper installation of base flashings and equipment curbs, slit the corners of the sheet metal covers and vents and bend up sides which counterflash roof base flashings sufficiently to allow for the roofing work.
C. Decking: After all the built-up roofing, insulation, etc. has been removed, the deck shall be thoroughly inspected for traces of deterioration. If deck damage is present, repair or replace with the RHPO's approval before proceeding. (Cost of deck repair will be paid on a change order basis as a concealed condition).
D. Vapor Retarder (at new metal decks only): Install loose laid on deck just ahead of insulation. Lap all joints 2" minimum and tape joints with flame spread rated accessory foil scrim tape. Extend to top of cants. Cover retarder with insulation board or cricketing layer(s) and mechanically fasten board as specified elsewhere. Install mechanical fasteners in insulation board or cricketing layer(s) having minimum 1-1/2" thickness.
E. Wood Nailers:
- Install treated wood nailers at all perimeter metal edge flashings, metal flanges of roof top equipment, pitch pockets, vent stack leads and equipment support legs.
- Nailer should be equal in thickness to the insulation.
- Installation at Metal Decks:
- Mechanically fasten the approved insulation to the deck utilizing one of the approved fasteners.
- Fasteners shall be installed at a rate of one per every two (2) square feet of board.
- Installation at Concrete Decks:
- Prime concrete deck with one gallon primer per 100 sq. ft.
- Install the approved insulation to the deck in a uniform application of Type III hot asphalt at a rate of 30 lbs. per 100 sq. ft.
- "Walking in" the insulation boards is required to assure good contact and uniform adhesion.
- Cover Board: Install over insulation as top layer. Use mechanical fasteners at metal deck. Hot mop with Type III hot asphalt, 30 lbs. per 100 sq. ft., at concrete decks.
- Insulation General:
- The insulation should be tightly butted together with the joints staggered. Offset joints from any substrate plywood joints.
- Installed insulation shall not be left exposed to the weather. It shall be covered and waterproofed at once. All exposed edges left at the end of the day's work shall be temporarily sealed. Remove the cut-offs as work progresses.
- 5. Crickets and Tapered Insulation:
- At the areas indicated, install new crickets to facilitate positive drainage.
- Crickets shall be constructed of layers of perlite set in Type III hot asphalt.
- Prior to installing the approved insulation, prime the cricket with manufacturer's recommended primer at a rate of one gallon per 100 sq. ft., then set insulation board in Type III hot asphalt at a rate of 40 lbs. per 100 sq. ft.
G. Cold Process Built-Up Roof Insulation:
- All felts shall be rolled onto the roof surface, cut in 18' lengths and allowed to relax in the hot sun a minimum of 30 minutes. (Felts shall be allowed to relax for longer periods of time on cooler days).
- Starting at the point of the roof, apply over the insulation a uniform coating of cold process adhesive at a rate of 3 gallons per 100 sq. ft.
- Embed into the cold process adhesive a 12", 24" and 36" wide strip of roofing felt. Overlap the 12" wide felt completely with the 24" and overlap this with the 36" wide roofing felt. Continue to install full widths of felt, overlapping the preceding felt by 25" in shingle fashion.
- Over all end laps, fully embed into the cold process adhesive one full ply of roofing felt, to hold down end curls, running perpendicular to the felt pieces.
- Felts will be extended their full length and lapped 4" creating a continuous joint at the felt ends.
- Each ply of felt including the starting felt shall be solidly coated the full width with at least three gallons per square and nowhere shall felt touch felt. The felt shall be broomed to assure complete contact without wrinkles, fishmouths or blisters.
- Extend all plies to the edge of the roof or to the top of cant strips and cut off evenly.
- Temporary water stops shall be installed at the completion of the day's work and removed before starting installation of the membrane the following work day. No unfinished roofing shall be left exposed overnight.
- Prior to the application of the top coating, all fishmouths shall be cut and reinforced with roofing felt and cold process adhesive. All ridges shall be cut and repaired with a 12", 24" and 36" ply of felt.
H. Base Flashings:
- Extend all roofing plies over the cant strip and cut off evenly.
- Apply sheeting bond 1/8" thick to the entire wall, cant strip, and onto the roof surface 6".
- Install hypalon base flashing.
- Sheeting shall be of sufficient width to cover the wall and extend onto the roof 4" beyond the lower edge of the cant except where reglet conditions are indicated.
- Secure the hypalon sheeting to the outside edge of the wood nailers (when provided) on the parapet walls and the top of the equipment curbs 8" on center with Simplex 1" square head roofing nails.
- Install metal copings, surface mounted reglets and counterflashings at the areas indicated to cover and secure all exposed fasteners.
- Seal all exposed vertical edges of base flashing with a 1/8" x 1" galvanized closure bar. Apply tape to wall; apply hypalon to tape; apply another layer of tape; apply closure bar to tape and fasten with fasteners at 6" on center.
- Seal the lower edge of the hypalon sheet with a three course application of Polyroof and 6" Burmesh.
- Splice all hypalon laps with sheeting bond and three course with Polyroof and Burmesh.
I. Metal Roof Flanges - perimeter metal edge, vent stacks, equipment pitch pockets, etc.
- Under all metal roof flanges install wood nailers of equal thickness to the insulation.
- Set all roof flanges on top of the roofing plies and in a bed of ELS mastic.
- Apply Polyroof between all metal edge lap joints.
- Nail the flange to the wood nailers with large head roofing nails 3" on center maximum.
- Prime with approved primer.
- Seal all flanges with a 5 course application of ELS mastic and 4" and 6" Burmesh.
J. Pitch Pockets:
- Pitch pockets shall be 24 gauge galvanized steel 3" high with a 4" roof flange.
- Pitch pockets shall allow for 2" of clearance between the penetration and the pitch pocket wall.
- Fabricate the top edge of the opening with a 1/4"- 1/2" hem bent to the outside.
- Solder closed all four corners.
- If the pitch pocket is used around an existing penetration and cannot be slipped over, then make it soldered or pop riveted.
- The pitch pocket is installed over the roofing plies and set in a bed of ELS mastic nailed securely to the wood nailer which is under the flange, using large head roofing nails 3" on center.
- Prime flanges with approved primer.
- The roof flange is 5 coursed with ELS mastic and 4" and 6" Burmesh.
- Fill the pitch pocket 2" with non-shrink grout.
- Fill the pitch pocket with Polyroof so that the water will shed off the top.
- Clean the pitch pocket interior with primer.
K. Drains (both new and re-used existing drains):
- Remove and lift drainage fitting clamps, rings, etc. on drains. Clean and store for later installation.
- Taper insulation to create a 48" x 48" sump around drain.
- Plug drains to prevent debris entry.
- Apply two layers of 1" caulking tape to the drain bowl.
- Install all roofing plies into the drain bowl.
- Discard existing lead sheets and replace with minimum 30" square, 4 lb. lead.
- Embed new lead in Polyroof and install on top of plies of built-up roofing system. Extend lead 1" beyond the clamping ring and bend down into the bowl.
- Flash edges of lead with a 5 course of Polyroof and Burmesh.
L. Lead Vent Pipe Flashings: Install over the completed plies bedded in with ELS mastic, nailed maximum 3" on center into wood nailers which are installed under the plies, the 5 coursed with ELS mastic and 4" and 6" Burmesh (Burmesh is covered with 1/8" of ELS mastic to cover green mesh).
M. Miscellaneous Flashing and Roof Top Equipment:
- Reinstall pipe and conduit flashings, reset ventilators on curbs and secure to match existing.
- Where corner metal flashings were or are opened and side of flashings bent up to allow space for working, bend flashings back down to the original position and fasten a prefabricated 24 gauge corner.
- Insert prefabricated sheet metal corners, lapped under a minimum 2" at sides and top, under all corners. Secure the position using a minimum of 4 pop rivets or self-tapping sheet metal screws.
- Any existing flashings, drainage fittings and wood blocks, which are damaged shall be replaced to match the existing as part of this work.
N. Cold Process System Protective Coating:
- Apply protective coating after all phases of the cold process roof have been completed leaving a watertight system with a solid smooth built-up roof base.
- Allow the cold process system to cure a minimum of 30 days.
- Prior to the application of protective coating, wash down the entire surface and allow to dry.
- Apply coating to the roof surface and base flashings at the rate of 4-1/2 gallons per 100 sq. ft. Care must be taken to assure uniform coverage and appearance. Excess piles and accumulation will not be accepted and must be brushed out.
O. Aluminum Reflective Coating:
- Allow the protective coating to cure a minimum of 30 days.
- Wash the roof surface and allow it to completely dry.
- Apply aluminum reflective coating to the roof surface and base flashings at a rate of 150 sq. ft. per gallon. Aluminum may be sprayed, rolled or brushed.
P. Traffic Toppings:
- Install traffic topping at the areas indicated.
- TremTreds (or approved other) are to be installed in a full liberal application of roof mastic.