Extending Roof Life

Short Term Repairs – How to extend the life of a low-slope roof for a few more years:

Note: If the roofing system is wet or damaged (see previous page) then trying to extend the life of the roof risks damaging or further damaging the deck or structural supports, which in the worst case can cause a roof collapse.

Quick single-ply primer (EPDM,TPO, PVC):

Single-ply membranes mostly include EPDM (rubber – black or white), PVC (plastic based – white, grey, tan or sometimes other colors) or TPO (plastic based – white, gray, tan or sometimes other colors). There is a much larger base of installed EPDM systems than TPO or PVC, although the ratio is changing. Single-ply membranes can basically be installed in 3 ways:
1.    Fully adhered (glued) to insulation or directly to the deck.
2.    Mechanically fastened with plates/bars through the insulation/roof deck.
3.    Ballasted (weighed down with 1″-2″ dia. stones).

TPO and non-reinforced black EPDM of the same thickness are the same price for the membrane but as TPO does not require seam tape to join the rolls of membrane, it is generally less costly.

If there are lots of projections to flash then TPO can be more costly as the labor for flashing pipes, curbs and height changes is greater, thus increasing TPO’s cost.

EPDM adhered, mechanically fastened or ballasted:

The first thing to fail with age on EPDM roofs are the field seams (where the rolls of EPDM are glued/taped together during roofing), the factory seams (where pieces of EPDM have been glued together to produce rolls in the factory) and flashings (extra EPDM wrapping around projections from the roof such as roof top units, pipes and drains). Depending on the craftsmanship used to install the roof, the amount of moisture, and structural stability, the seams and flashings may fail anywhere between 15-25 years. To prevent failures the seams can be covered (stripped in) with EPDM tape and the flashings can be re-done. We have seen seams treated with more sealant to extend their life but while that costs less it also lasts a shorter period of time.

The roof should be inspected for any holes or cuts and patched with EPDM. The perimeter edges should be inspected and repaired if any of the EPDM has pulled away from the metal securing the EPDM to the roof (drip edge, termination bar or coping). Make sure all the metal is secure and if not, re-secure or replace it. Clean up any spills of grease or oil. Do not use asphalt based products as they are chemically incompatible with EPDM (no asphalt roofing cement!). For ballasted roofs it is very labor intensive to check the membrane for cuts and slices because all the rock has to be shifted, the membrane cleaned, inspected and the rock shifted back – for this reason it seldom happens.

Remove all debris from the roof. Limit traffic to maintenance people only and check for damage after any contractors have been on the roof. Roofs are not generally designed to handle lots of traffic – in addition to people dropping sharp things, the insulation where people consistently step can be crushed. Check for ponding (see special ponding section on other page).

TPO and PVC:

TPO and PVC membrane are heat welded as the rolls and flashings are installed. This provides a stronger seam than EPDM provided the welding is done properly. If the welding is done poorly then the seams/flashings may fail after a period of time. Some of the problems found in the plastic based membranes occur from the different chemical make-up. Older versions of plastic membrane could crack and shatter in below freezing temperatures. Splits and holes can also occur. Seams and flashings welded properly should last as long as the membrane. Slices and cracks are the most problematic issues with plastic based single-ply membrane. TPO and PVC are made up in a sandwich with plastic on top, mesh in the middle, and more plastic on the bottom. As the mebrane ages the plastic on top wears away. If the mesh is visible it is time to replace the membrane. Proper patches require heat welding a piece of similar material. Check for ponding (see special ponding section on other page).

Modified Bitumen / Bald asphalt:

Modified bitumen is an asphalt based roofing material that comes in rolls and those rolls are either adhered to the insulation/roof deck with adhesive or hot asphalt. The seams between the asphalt rolls are torched and mated together. We don’t see alot of modified bitumen in New England, we assume the use of fire when applying the roofing plays a part. Bald asphalt has an asphalt layer with no gravel on top. After a certain amount of years the oils dry out and cause the roofing material to crack. Modified bitumen and bald asphalt roofs can either have more modified bitumen pieces torched onto cracks/holes/flashings or asphalt roofing cement with reinforcing mesh can be used. If the mesh is not used the asphalt roofing cement by itself shrinks and cracks. Coatings of petroleum based products (resaturants) or non-petroleum based products can be used to fill cracks over wide areas. These seem to last 2-5 years. Some coatings will take extra measures and may last into the 10 year range. Check for ponding (see special ponding section on other page).

Asphalt/Coal Tar Pitch and Gravel:

Asphalt and coal tar pitch are different grades of petroleum derivatives. These products are combined with layers of felt then topped with small gravel (to protect the roofing from ultraviolet rays) to constitute a roof. After a certain amount of years the oils dry out and cause the roofing material to crack. Coatings can be of petroleum based products (resaturants) or non-petroleum based products. The petroleum based products have been in use longer and likely work better. Asphalt roofing cement and fiberglass mesh can also be used to repair small problems. Pitch roofs (which smell like kerosene) usually last the longest. Pitch has a lower melting point and can sometimes melt into cuts or cracks in high summer heat, making pitch roofs the longest lasting of any we have come across. Check for ponding (see special ponding section on other page).

Spray Foam:

There are very few spray foam roofs in New England. We offer no information on extending the life of spray foam roofs.

Metal Roofs:

Metal roofs generally have 3 problem areas.
1.    The fasteners loosen or the rubber washers deteriorate and leak.
2.    The seams leak where the metal panels join together.
3.    The panels themselves rust.

Coatings can be applied to a metal roof. If the coating includes special material like fabric mesh at the seams and fasteners then the coating can last more than 5 years. If special measures are not taken at the fasteners and seams the expansion/contraction that the metal goes through over the seasons will cause the coating in those areas to fail. Coating the roof without applying mesh at the fasteners and seams will only temporarily stop leaks but will prevent or slow the panels from rusting out. For the coating to stick to any rusty metal the metal usually has to be prepped by sanding and treated with some type of rust inhibiting primer. Tightening up the fasteners may temporarily stop them from leaking. Adhering EPDM to seams and caulking fasteners will also stop leaks for a period of years. Applying asphalt roofing cement to problem areas rarely lasts and makes applying better/future fixes more difficult.

Re-roofing a section:

Some roofs only have a section or small area that has trouble. It is possible to re-roof a section. When re-roofing a section a number of items must be considered. It is better to define the top end of a section at the peak of a slope so no future leaks from the older, higher area at the top of the slope flow into the newly roofed section. A barrier of sealant, wood and membrane can be built up to stop water flowing between old and new sections if necessary. If the deck is fluted metal the flutes may have to be foamed as well. Consideration should be given to the thickness of the replacement roofing – if the new roofing is higher or lower than the adjacent area people could trip or water could pond. Unless the waterproofing systems are the same then warrantees are rarely provided at the tie in’s to the older areas. Cutting out areas in asphalt based roofs generally causes damages on the adjacent “good” area edges. Traffic to re-roof one area can cause problems on the adjacent “good” areas as personnel and machinery cause cracks in asphalt roofing or damage to single-ply membrane or metal roofs. Sometimes the cost differences between roofing a smaller and a larger area are not that great due to the same fixed costs involved with roofing both areas – cranes, dumpsters, travel, meeting/supervision and warranties, so multiple prices should be requested from your roofing contractor.


There have been and will continue to be coating manufacturers that make claims to provide a complete, long-lasting waterproofing system. We have seen many coating systems fail over the years. The failures seem to occur because the material directly under the coating moved, the chemical composition of the coating peeled or, moisture or air came from underneath the coating or was encapsulated when the coating was applied. We used to believe that coatings were not good for waterproofing but only for reflecting sunlight. We believe that coatings can be proper water-proofing layers if the surface is prepared properly and the coating applied correctly. Coating manufacturers claim to be useable on all types of roofing. We believe the most appropriate place for a coating is on a metal roof. To do this correctly usually has to meet a host of conditions:
1.    The temperature range usually has to be over 40 degrees Fahrenheit and less than some temperature (depends on coating).
2.    The fasteners have to be treated first with mesh or extra caulking.
3.    The seams have to be treated with mesh.
4.    Excess rust has to be treated.

We have priced out applying coatings to EPDM roofs – the coating manufacturer required a foundation coat, mesh over the entire roof in that coat, another foundation coat then 2 finished coatings. This ended up costing much more than adding a new layer of insulation and an EPDM membrane. Coating a modified bitumem or built-up roof may also yield a few extra years of leak relief.

Looking for leaks with equipment:

We have discussed on the previous page looking for wet insulation with an infra-red camera and with a nuclear gauge. Having one done on your roof periodically is not a bad idea as any wet insulation will tell you there are leaks. Some leaks are pinholes and don’t incur enough water to be noticeable from below but will do damage over time. This is especially true if your insulation absorbs water well (like fiberboard) and the water spreads sideways through the insulation instead of dropping through the nearest hole in the deck. Another technique for leak detection uses electricity. We have not seen this in action but hope to in the near future. This method seems to work best on roofs with metal decks and most waterproofing layers except EPDM (black rubber). The basic principle is to use water to conduct electricity. A wire loop is placed around an area, the area is wet down with a hose, and an electrical charge is generated through the wire. If there is a hole the electricity will follow the water down through the hole to the metal deck and change the electrical field, which can be measured and mapped with the proper equipment. This technique can be used on an existing roofing system or when re-roofing or newly roofing a building. During roof installation it is possible to embed a grid of wires or special tape in the roofing system and, generating a electric field, have a leak discovered by equipment when it occurs. The folks at Detec Systems tell us it is possible to monitor it over the Internet. We expect this technique to grow in the future as building owners and roofing specifiers are made aware of this technology. For more information on this check out these web sites (www.leak-detection.com and www.detecsystems.com).

Final thoughts:

A roof doesn’t exist in a vacuum so may be victim to falling branches, destructive humans, high winds, lightning or shifting of the structure, all of which may cause leaks. If you absolutely can’t have water hit the inside of the building then make sure there is a secondary layer of waterproofing under the roof. If you don’t want a secondary layer and just really don’t want leaks then:
•    Clear away all branches/trees from the sides of the building
•    Limit human traffic on the roof or at least unattended human traffic
•    Make sure the roof is inspected initially by the manufacturer
•    Have the roof inspected periodically and after any storm by someone with sharp eyes, roofing knowledge and patience.