What is a Built-Up Roof and why should I use it? The what and how of built-up roofs Built-Up Roofing, or BUR for short, first appeared around the mid 1800’s. It is a roofing system where multiple layers of asphalt get applied between ply sheets (or felts) over the roof deck and insulation. Exploded diagram of a built-up roof
- 1 What is the life expectancy of a built-up roof?
- 2 How do you know if a roofer is ripping you off?
- 2.1 How thick is built-up roofing?
- 2.2 How long does a flat built up roof last?
- 3 Is a built up roof the same as modified bitumen?
What’s another name for built-up roofing?
Built-up Roofing – Production Process & Properties – Built-up roofing systems, referred to as BUR, have been in use in the U.S. for over a century. This roofing system is also known as a “tar and gravel” roof. BUR systems are typically composed of alternating layers of bitumen and reinforcing materials that create a membrane.
- Substrate or Decking
- Roof Insulation
- Roofing Asphalt
- Venting Base Sheet (Cover Board) with Roofing Asphalt
- Ply Sheet with Roofing Asphalt
- Slag or Gravel in Asphalt or a Modified Bitumen Cap
- Note: When a modified bitumen membrane is used to cap a BUR system, this combination is referred to as a “hybrid” system.
- Roofing asphalt (bitumen) commonly used in BUR systems includes:
- Asphalt – Asphalt (a petroleum product refined from crude oil) requires heating before application with a mop or spreader
- Coal Tar – Coal tar (derived from the distillation of coal) also requires heating before application with a mop or spreader
- Cold-Applied Adhesives – These adhesives are solvent-based asphalts that don’t require heating prior to application
- Surfacings used on BUR systems may be (or a combination of):
- Aggregate – Gravel, slag, crushed stone, and/or mineral granules are common aggregates
- Cap Sheets – Commonly made with glass-fiber or mineral surfacing
- Asphalt – Hot Asphalt spread or mopped over the entire surface
- Alternative Coatings – Aluminum and elastomeric coatings are commonly applied as surfacing for BUR systems
Can you walk on a built-up roof?
Page 3 – No matter your roof type, it isn’t prudent to walk on a roof. That is, you should avoid it as much as possible. Walking on a roof should be left to professional, If it’s a less significant issue that can be fixed without involving a roofing contractor, you can consider walking on a flat roof.
- Because compared to other roofs, flat roofs pose fewer risks.
- When you walk on your roof, you place pressure on it, resulting in cracks, shifting, or holes in the membrane.
- And if not properly taken care of, it will cause more damages to your roof.
- But the exciting news is that there is the right way to walk on your roof.
So how can you walk on your roof?
What is the life expectancy of a built-up roof?
2. Built-Up Roofing (BUR) – BUR consists of several layers, including a bottom layer or two insulation boards, multiple intermediate layers of asphalt or tar with layers of felt, and a layer of gravel. This results in a tough, thick, and seamless roof assembly which resists damage.
Is built up roofing good?
Pros and Cons of Built-Up Roofing – Built-up roofs tend to provide excellent waterproofing and ultra-violet protection. Thanks to the aggregate top layer, they are also fire-resistant. Built-up roofing is generally low-maintenance and therefore costs little to maintain over its life.
What is the top layer of a built up roof?
Built-Up Roof system A system of interacting roof components generally consisting of a membrane or primary roof covering and roof insulation (not including the roof deck) designed to weatherproof and sometimes improve the building's thermal resistance. ” href=”https://parsonsroof.com/glossary/roof-system” data-gt-translate-attributes=””>Roof system or BUR system is a common built-up Commercial Roofing system provided by Parsons Roofing Company, Bitumen (1) A class of amorphous, black or dark-colored, (solid, semi-solid or viscous) cementitious substances, natural or manufactured, principally composed of high-molecular-weight hydrocarbons, soluble in carbon disulfide, and found in asphalts, tars, pitches and asphaltites; (2) a generic term used to denote any material composed principally of bitumen, typically asphalt or coal tar. ” href=”https://parsonsroof.com/glossary/bitumen” data-gt-translate-attributes=””>Bitumen is the first Adhesive A cementing substance that produces a steady and firm attachment or adhesion between two surfaces. ” href=”https://parsonsroof.com/glossary/adhesive” data-gt-translate-attributes=””>adhesive layer and roofing Felt A flexible sheet manufactured by the interlocking of fibers with a binder or through a combination of mechanical work, moisture and heat. Felts are manufactured principally from wood pulp and vegetable fibers (organic felts), asbestos fibers (asbestos felts), glass fibers (fiberglass felts or ply sheets) or polyester fibers; other fibers may be present in each type. ” href=”https://parsonsroof.com/glossary/felt” data-gt-translate-attributes=””>felt is installed in multiple plies over the base layer of a commercial roof. The top layer consists of stone, Gravel Coarse granular aggregate, with pieces larger than sand grains, resulting from the natural erosion of rock. ” href=”https://parsonsroof.com/glossary/gravel” data-gt-translate-attributes=””>gravel, crushed Slag (1) A hard aggregate that is left as a residue from blast furnaces; may be used as a surfacing material on certain (typically bituminous) roof membrane systems. See blast furnace slag; (2) the fused agglomerate which separates in metal smelting and floats on the surface of the molten metal. ” href=”https://parsonsroof.com/glossary/slag” data-gt-translate-attributes=””>slag, or other aggregates. Typically, a built-up roof lasts anywhere between 15 and 30 years, BURs work well in warm climates since the BUR overlays are designed to cool the roof. Multiple layers also increase resistance to surface damage, which means they incur fewer built-up roofing repairs. A built-up roof lasts anywhere between 15 and 30 years even in warm climates when installed correctly by Parsons Roofing Company, the Best Commercial Roofing Company.
How do you know if a roofer is ripping you off?
Reducing Labor Time – Another reason a roofer is ripping you off: they’re duping you of their quality and their time. We’ve all heard that “time is money.” If you pay thousands of dollars on a roof replacement, you expect outstanding-quality work from your roofing contractor.
How thick is built-up roofing?
How thick is built-up roofing? – A BUR roof system comes in multiple layers, most often between two and four. The thickness depends on the materials used and the number of built-up roofing layers applied, but typically the selvage area ranges between two to four inches.
How do you install a built-up roof?
The Basics of Built-up Roofing – Exterior Home Services Built-up roofing is one of the oldest roofing processes in the modern era. That’s for good reason. Built-up roofs are effective at repelling water and resisting leaks. They also hold up well and look nice.
If you are thinking about installing one of these flat roofs on your home or commercial building, you might have some questions about the roof installation process. Here are some basics of built-up roofing everyone should know. The Process Installation of built-up roofs occurs in four steps. First, contractors attach base sheets to the roof’s subsystem using roofing nails.
Then, they use tar, concrete, adhesive, or asphalt to glue down felt over the top of the base sheeting. Next, roofers install a layer of gravel or cap sheets, which they then cover with a final layer of asphalt. When the process is complete, the house or commercial building has a virtually impenetrable covering to keep elements at bay.
Assistance The four steps of built-up roof installation are probably sufficiently technical to deter even avid DIYers from tackling the project themselves. That’s a good thing. Not many homeowners have the equipment required to heat or spread adhesive. They also don’t typically have the skill to effectively distribute gravel.
Nonetheless, the real deal breaker for most homeowners is the weight of the roofing materials. Without exaggeration, the adhesive, gravel, and asphalt required to install an effective built-up roof can weigh hundreds of pounds. Thus, the safest way to install a built-up roof is to ask for assistance for a skilled roofing contractor.
Planning If you have a roof emergency, you might need immediate roofing help. If you have some time, though, try to plan your built-up installation. By picking a cool, dry season, you can make the installation process much more pleasant for your roofing crew. If you need a built-up roof installation, you should keep a few basic things in mind.
Most importantly, though, you should remember it probably isn’t the type of job you should do yourself. : The Basics of Built-up Roofing – Exterior Home Services
How often should a built-up roof be replaced?
How Long Does a Built-Up Roof Last? – In general, a properly installed built-up roofing system will last 20 to 30 years. However, a lot depends on the quality of the installation of the roof, as well as the number of layers (also know as piles) it has. Each layer will get you approximately five years, but no system will have less than three layers.
What type of roofing lasts the longest?
Roofing material that lasts the longest are concrete, clay or slate tiles. These materials significantly outperform other natural products like wood shakes or any manufactured roofing materials including asphalt shingles and metal roofing. Although these materials have a good lifespan, they are not as durable.
How long does a flat built up roof last?
Factor In the Material – The materials used to make a flat roof play a large part in determining its lifespan. A multi-layer built-up roof consisting of waterproof material, hot tar and gravel can last for 15 to 20 years. Roofs consisting of three to five layers of modified bitumen have a slightly shorter average lifespan of 10 to 15 years.
These materials are heavy and may not be the best choice for every building. Lightweight single-ply roofing can last for as long or longer than layered roofs depending on the properties of the material, the design of the roof and reliance on commercial roof repair. EPDM and TPO roofing generally last anywhere from 10 to 20 years, while TPO roofs have stronger seams than EPDM roofing.
With proper maintenance, a PVC roof can last up to 30 years.
Is TPO built up roof?
TPO vs Tar and Gravel or Built-Up Roof (BUR) Flat Roofs Some commercial and residential roofs use Tar & Gravel or Built-Up Roof (BUR) as a roofing solution. Let’s look at both solutions. Both solutions work on a little to no slope type of roof. First let’s define what a Tar & Gravel or Built-Up Roof (BUR) is.
- It’s made up of 3 to 5 laminated layers, hot tar and roofing felt.
- It also has a layer of bitumen and an aggregate top layer.
- It’s been used for well over 100 years.
- It works, but there are some disadvantages which we’ll get into shortly.
- What’s a TPO roof? As we’ve mentioned in other posts, a TPO, Thermoplastic Polyolefin, roof is a thin rubber like single ply roofing material for low-slope roofs.
It’s been used on commercial and industrial roofs since the late 1980s in both the US & Europe. It was initially used in pond liners and the auto industry. It is an alternative solution to other roofing materials such as PVC, EPDM & others and usually cheaper.
So what gives? I have a flat roof what should I choose for a roofing solution: TPO or Tar & Gravel? Let’s looks at the advantages and disadvantage of both. Both TPO & Tar & Gravel can be about the same price depending on the installer and product used. However, that’s just about the only point where they are the same.
Often times you will find that TPO is actually cheaper with many advantages whereas Tar & Gravel has more disadvantages. When it comes to environmental questions both help with UV light in that it will reflect or absorb the UV light for roof longevity.
- However, TPO is cooler in the summer and warmer in the winter due to TPO reflecting and absorbing heat depending on the color used since TPO can be white, black or gray.
- What are other environmental considerations? A Tar & Gravel roof with tar, felt and fiberglass isn’t recyclable at all.
- Whereas, A TPO roof is 100% recyclable.
As anyone that has ever been around tar knows, it smells. It’s bad for the installers as well as the people around it when it’s being installed. Granted it’s a short-lived inconvenience for the building owner, not so much for the installers. They deal with it frequently.
- A TPO roof doesn’t have that smell, is safe for the installers and is energy star rated.
- A Tar & Gravel roof is not due to inconsistencies in depth.
- More on that later.
- What about installation? A Tar & Gravel roof can take longer to install than a TPO roof as it has to be “created” on site.
- Remember the smell we mentioned earlier? A Tar & Gravel roof, since it’s “created” on site doesn’t have a consistent thickness.
You will have some areas that are thinner than other areas. Whereas a TPO roof is manufactured so thickness is consistent across the roof. Both Tar & Gravel and TPO use heat to install but in VERY different ways. Tar & Gravel, as mentioned above, has multiple layers which involves heated layers.
Did we mention the smell? Whereas TPO uses heat to “heat weld” the seams. One final point worth mentioning. Depending on the thickness of the Tar & Gravel roof your roof may need to be reinforced to accommodate the additional weight vs. a TPO roof which is no issue with regard to weight. Let’s consider if something goes wrong.
Both roofing solutions can be walked on. Both are waterproof depending on how well the installer does the install. But what if a leak happens? Leaks in a Tar & Gravel roof can be very difficult to find. Think about it from this perspective. Try finding a water path when pouring water through rocks in a garden.
It’s not easy. It goes all over the place. That’s how a Tar & Gravel roof is since it has aggregate. That’s not to state that a leak can’t be found, but it’s not as easy as TPO and could be more challenging to repair. Whereas a TPO roof leak can be found and sealed using different techniques. It’s similar to finding and sealing your favorite pool float or inner-tube.
You find it, patch it and walk away knowing that it’s truly found and sealed. Final thoughts. We most certainly advise customer to use TPO instead of a Tar & Gravel roof based on what we’ve mentioned above. It’s cheaper, more environmentally friendly and, generally, easier to repair should something happen.
Can you overlay a built up roof?
Difference Between Reroofing and Roof Replacement – Roofing over an existing roof is also called reroofing or an overlay. It is the process where roofers install a new roof over your existing one, i.e. add a new layer of shingles, which means that there is no tearing off of the old roof.
- It is important to know that this process can only be done once because you can only have two layers of shingles on your roof.
- Roof replacement is the process of installing a completely new roof that includes tear off of the old one.
- Roofers will tear everything off, down to the deck of the roof, and basically start from scratch with the new roof, from putting felt paper to installing shingles.
Since roof replacement includes tearing everything off, it can be done on every roof, no matter the number of shingle layers – they are all going to be removed in any case. Roof replacement involves much more time and labor, and is, therefore, more expensive than reroofing.
What is a built up shingle?
BUR Multi-Ply Built-Up Roofing – Asphalt Roofing Manufacturers Association (ARMA) Why is a built-up roof considered a multi-ply roof? ARMA defines a built-up roofing system as a roof where multiple layers of asphalt alternated with ply sheets (felts) are applied over the roof deck (vapor retarder) and, most often over insulation that is attached to the roof decking.
- Ply Sheet
- Ply sheet
- Ply Sheet
- Cover Board
- Rigid Roof Insulation
- Why is a multi-ply better than a single ply?
- Multi-Layer Protection
- The multiple layers of bitumen and bitumen-saturated “felts” make a water-resistant barrier capable of providing many years of reliable protection from the elements.
- If the top layer is damaged, the subsequent layers underneath provide a back-up layer to stop water and the elements from entering the building.
- The multiple layers create a more rigid and stable surface that make the roofing system more applicable to being a platform for your mechanical systems, solar energy systems, vegetative (roof gardens) or creating usable outdoor space by installing a roof deck over top of it.
- Many single-ply roofs these days are installing “sacrificial layers” underneath solar arrays; mechanical areas; and in high traffic areas to protect the primary membrane from damage.
- Are BUR multi-ply roofs energy-efficient?
- Thermal Performance
- Built-up roofing systems exhibit exceptional resistance to the conduction of heat between the exterior and interior of a building, resulting in noticeable reductions in heating and cooling costs.
- BUR incorporates the roofing insulation into the monolithic roofing membrane and results in better insulation or a higher R value for better thermal performance your roofing system can achieve.
- BUR may have a ballast layer added to them (local building code permitting) which can increase the thermal performance.
- A BUR system generally incorporates insulation in the design of the roofing system because of the multiple layers increasing the insulation properties that can boost the energy efficiency of the system.
- How does my BUR multi-ply roof provide added protection?
- Fire and Uplift Resistance
- Built-up roofing systems are tested through Underwriters Laboratories and Factory Mutual Research Corporation to meet very strict fire resistance requirements and ensure adequate uplift resistance under extreme wind conditions.
Uplift: The BUR systems continuously adheres each layer to one another forming a monolithic structure without the need for fasteners. This monolithic layering reduces the number of penetrations and stress points caused by fasteners and increases wind resistance.
- Fire Resistance: FM1 include the highest fire rating available.
- UL Class A is the best in the industry.
- Can an asphaltic BUR roof be used to meet cool roofing standards; earn USGBC LEED points; and meet Energy Star program requirements? Yes, multiple options exist to make a black BUR into a highly reflective or “cool” BUR: A BUR can be coated with UV reflective material to become a more highly reflective “cool” roof.
This is typically done with an aluminum coating to increase the surface reflectivity. A highly reflective white coating can be used but special precautions must be taken to ensure the white coating does not yellow over time due to a phenomenon called bleed-through.
- A BUR system can be covered with a white granulated cap sheet to meet cool roofing requirements.
- Ballast may be added.
- Is a multi-ply BUR economical?
- Compared to other high performance commercial roofing systems, built-up roofing is one of the best investments on the market today due to its competitive cost per year of expected service life.
- Low maintenance: Recommended annual inspection to check for clogged drains, gutters, pitch pockets needing to be tipped off, damage caused by a service repairman, etc.
- A multi-ply smooth surface BUR system can be restored by resurfacing a flood coat of asphalt, a fibered aluminum roof coating, a white or pigmented elastomeric roof coating, and/or asphalt coating and gravel.
Multiple-ply means fewer headaches, when using the roof as a platform for your vegetative roof, solar array or outdoor living space. The multiple ply provide added protection so there’s no need for expensive deconstruction of items inhabitation the roof to affect repairs like single-plies.
What advances have been made with BUR? As technology has advanced, so has BUR application. In addition to the development of low-fuming hot applied asphalt, hot mopped jobs are giving way to new applications like cold applied. Cold-applied applications reduce exposure to potentially irritating fumes; and the need for hot kettles, while still providing many if not all of the benefits and applications listed above.
: BUR Multi-Ply Built-Up Roofing – Asphalt Roofing Manufacturers Association (ARMA)
Is a built up roof the same as modified bitumen?
Modified Bitumen – Modified Bitumen (MB) roofing is an asphalt-based, close cousin of the Built-up-Roof (BUR) designed for buildings with low-slope or “flat” roof structures. Engineered modified bitumen roofing membranes originated in Europe in the mid 1960’s and have been used successfully in the United States and Canada since approximately 1975.
Modified Bitumen roofs give designers and installers an even broader array of options than BUR. MB may be installed by the torch-application method, or “hot-mopped” like BUR, or applied with “cold-process” adhesives. The latest innovation with MB is the self-adhering sheet. Using special combinations of polymers to modify the underside of the MB sheet, the rolls are manufactured with a release paper.
The installer removes the release paper and as the sheet is rolled out, it adheres itself to the substrate. This method eliminates the risks associated with the use of torches, hot asphalt, and is completely free of VOC (volatile organic chemicals) fumes during and after application.