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 (restaurants) 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).
Author Archive for Ann – Page 5
There are very few spray foam roofs in New England. We offer no information on extending the life of spray foam roofs.
Metal roofs generally have 3 problem areas.
- The fasteners loosen or the rubber washers deteriorate and leak.
- The seams leak where the metal panels join together.
- 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.
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:
- The temperature range usually has to be over 40 degrees Farenheit and less than some temperature (depends on coating).
- The fasteners have to be treated first with mesh or extra caulking.
- The seams have to be treated with mesh.
- 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.
Figuring out re-roofing needs for low slope roofs starts with knowing what materials make-up your roofing.
One or more test cuts can determine the materials and deck type. Most low slope roofs have the insulation immediately above the deck and the waterproofing layer on top of the insulation. Sometimes there are multiple layers of roofing systems. The deck type usually can be determined from underneath (you may have to pop a few ceiling panels). See our test cut page for examples of what different material looks like. Anyone can cut into a roof but most roofs need to be patched by a professional. For example – asphalt based patching products are chemically incompatible with most single ply membranes.
Next step is to determine the condition of the materials. This determines whether or how much roofing material needs to be removed or replaced.
The no risk, high dollar approach is to rip off everything, inspect and replace damaged decking, then go back with whatever roofing system you choose. This option is favored by many roof consultants and roofers as they are guaranteed there is no moisture remaining in the roofing or damage to the deck. Under certain conditions this is the proper approach. Under other conditions this is wasteful of the owner’s resources and un-friendly to the environment. Removing the roofing to the deck incurs larger costs for the labor and disposal of the old roofing material as well as the usual installation of thicker insulation to meet your state’s building code.
If the deck is visible from underneath that is the first place to check. Rust, flakes, soft spots, sagging, discoloration all point to deck problems. The other way to check is through test cuts. Take a 2′ x 2′ test cut and examine the deck. Some deck issues like rust will not show up from the bottom until too late. Examining the deck from above takes some experience. Metal decks should be inspected for rust and poked with some gusto to make sure the metal is solid. Wood decks should be poked also to make sure they are solid. Concrete decks are trickier. Some concrete decks utilize lightweight concrete or gypsum to provide the slope in roof. Some roof decks are completely lightweight concrete or gypsum. There are some very strange combinations of materials on some older buildings. Once in a while ponding on a roof can point to deck problems (usually the problem lies within the roofing system).
If there are major deck problems the entire roof should be removed and the deck issues addressed. If there is a small area with problems it may be cost effective to only remove the roofing in that area, replace or repair the decking, then install new roofing material to the height of the adjacent roof area. If the condition of the deck is suspect and the new roofing system you choose utilizes mechanical fasteners (or adhesive directly on the deck) to secure either the insulation or waterproofing layer a pull test should be done. This involves screwing a fastener into the deck and utilizing equipment that measures the force (lbs.) required as it pulls the fastener straight out of the deck. The roofing manufacturer of your intended system should be able to perform the test and tell you what length warranty is available based on the test. The same principal applies to a pull test with adhesive. A pull test is especially important for metal roof go overs. The pull test also may help decide the fastening pattern required to meet certain wind uplift scenarios.
Moisture in the roofing system is bad. It attacks a roofing system in many ways. It works its way down to rust or rot the deck. It turns into gas when heated and attacks the seams, penetrations and other weak spots trying to escape and causes earlier failure. It freezes in the cold and lowers the thermal resistance, increasing heating costs. The freeze/thaw can cause excessive shifting of the waterproofing layer causing earlier failure. If moisture is in a roofing system it should be removed. However, a cost saving approach can be taken to remove just the layer or area that contains the moisture.
The answer to this depends on how many and what type of roofing system you have. Test cuts can be done at different spots on the roof. This is the only certain way to tell if there is moisture in the roofing system(s). Test cuts should be done anyways to determine the make-up of the roofing system(s). Since water runs downhill, test cuts should be taken near drains and gutters, as these areas are the most likely to contain moisture. Test cuts by themselves don’t pinpoint the exact wet areas. For that a moisture scan is needed. We are familiar with two main types – the nuclear scan and infra-red scan. Infra-red scans are done in the early evening as the air temperature cools down. Any wet areas in the roof will retain heat longer than the surrounding areas and an infra-red camera can pick up the thermal differences. A nuclear scan can be done at any time of day. To do the nuclear scan the roof is sectioned off into an imaginary grid, usually 10′ x 10′, and at each intersection point the device is placed on the roof and a reading is taken. The higher the reading the more likely moisture exists. Both moisture scans should be confirmed with test cuts.
Test cuts need to be patched properly to last. Materials similar to the to the roof’s waterproof layer need to be used (asphalt cannot be used on rubber, etc.) and any asphalt patches should use embedded fiberglass mesh. Plastic based membranes (TPO, PVC) should have the seams of the patch heat welded. If the roofing system is under warranty it is usually a requirement to have certain qualified contractors do any work (check the warranty language). The infra-red and nuclear tests have their limitations. The infra-red, which is the least expensive and easiest, does not work well on ballasted single ply systems or show moisture well in anything but the top roofing system if there is more than one. The nuclear is more labor intensive hence costs more. If there are multiple roofing systems then utilizing both provides the most accurate reading.
Roofing Systems & Components – Examples
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