Roofing Basics

A leaky roof can damage ceilings, walls, and furnishings. Roofers repair and install roofs made of tar or asphalt and gravel; rubber or thermoplastic; metal; or shingles to protect buildings and their contents from water damage. Repair and reroofing—replacing old roofs on existing buildings—makes up the majority of work for roofers.

There are two types of roofs—low-slope and steep-slope. Low-slope roofs rise 4 inches per horizontal foot or less and are installed in layers. Steep-slope roofs rise more than 4 inches per horizontal foot and are usually covered in shingles. Most commercial, industrial, and apartment buildings have low-slope roofs. Most houses have steep-slope roofs. Some roofers work on both types; others specialize.

Most low-slope roofs are covered with several layers of materials. Roofers first put a layer of insulation on the roof deck. Over the insulation, they often spread a coat of molten bitumen, a tarlike substance. Next, they install partially overlapping layers of roofing felt—a fabric saturated in bitumen—over the surface. Roofers use a mop to spread hot bitumen over the felt before adding another layer of felt. This seals the seams and makes the surface watertight. Roofers repeat these steps to build up the desired number of layers, called “plies.” The top layer is glazed to make a smooth finish or has gravel embedded in the hot bitumen to create a rough surface.

An increasing number of low-slope roofs are covered with a single-ply membrane of waterproof rubber or thermoplastic compounds. Roofers roll these sheets over the roof’s insulation and seal the seams. Adhesive, mechanical fasteners, or stone ballast hold the sheets in place. Roofers must make sure the building is strong enough to hold the stone ballast.

A small but growing number of buildings now have “green” roofs that incorporate plants. A “green” roof begins with a single or multi-ply waterproof layer. After it is proven to be leak free, roofers put a root barrier over it, and then layers of soil, in which trees and grass are planted. Roofers are usually responsible for making sure the roof is watertight and can withstand the weight and water needs of the plants.

Most residential steep-slope roofs are covered with shingles. To apply shingles, roofers first lay, cut, and tack 3-foot strips of roofing felt over the entire roof. Starting from the bottom edge, the roofer then staples or nails overlapping rows of shingles to the roof. Roofers measure and cut the felt and shingles to fit intersecting roof surfaces and to fit around vent pipes and chimneys. Wherever two roof surfaces intersect, or shingles reach a vent pipe or chimney, roofers cement or nail flashing-strips of metal or shingle over the joints to make them watertight. Finally, roofers cover exposed nailheads with roofing cement or caulking to prevent water leakage. Roofers who use tile, metal shingles, or shakes (rough wooden shingles) follow a similar process.

Roofers also install equipment that requires cutting through roofs, such as ventilation ducts and attic fans. Some roofers are expert in waterproofing; some waterproof and dampproof masonry and concrete walls, floors, and foundations. To prepare surfaces for waterproofing, they hammer and chisel away rough spots or remove them with a rubbing brick, before applying a coat of liquid waterproofing compound. They also may paint or spray surfaces with a waterproofing material or attach waterproofing membrane to surfaces. Roofers usually spray a bitumen-based coating on interior or exterior surfaces when dampproofing.

 

Roof & Attic Insulation

Insulating the attic of a house is important for heating and cooling inside the house. However, the ideal temperature of the attic/roof area is as near to the outside temperature as possible to prevent unnecessary condensation. Therefore, insulation should first be applied between the ceiling joists; this will allow insulation of the living areas of the home, without creating too much heat in the well-ventilated attic area. Additionally, insulation should never block inside or outside vents.

If the roof decking is the ceiling (as is the case with tongue and groove decking, with no attic space), insulation can be added in the form of rigid insulation on top of the decking rather soft insulation in the attic.

Roof & Attic Ventilation

Ventilation is an integral part of making a roof last, and occurs naturally when vents are placed at the base of the roof (at the eaves or in the soffits) and near the top of the roof (the ridge) so that warm air can leave through the top, and cool air can be drawn through the bottom. This process does not need electrical or mechanical fans in most cases, as nature will do the work on its own.

When vents are placed you should be aware of the following guidelines:

1. Vents should not be inserted into the middle sections of the roof, since this will often interrupt the natural circulation of the air. Instead, evenly distribute vents along the roof, to ensure even airflow to all portions of the roof.
2. Approximately half of the vents should be placed near the ridge and the other half near the eaves or soffits, to encourage maximum airflow.
3. Approximately 1 square foot of ventilation per 300 square feet of attic floor space should be included in the plans for your new roof (this is an approximate and depends on climate, roof pitch, orientation and available attic vent space).

Types of Attic Vents

1. Soffit Vents - Able to be used as either inlet or outlet of air they are best combined with a ridge or roof vent.
2. Gable End Vents - Vent placed at the top of the gable area on both ends of the house.
3. Ridge Vents - Vent placed along the entire ridge of the roof to allow hot air to escape as it rises to the top of the attic space.
4. Roof Vents - Available in a standard or powered version this vent is best installed toward the top of the roof .

If adequate ventilation is not installed, serious problems such as attic condensation, wood rot, mold, mildew and rusting metal will occur. These problems can affect the integrity of the roof as well as the integrity of the house, and can even cause health problems for family members in the home. One of the biggest roof problems associated with improper attic ventilation is an "ice dam".

House Rain Gutters

Infomation on Rain Gutters

Gutters and downspouts perform the simple function of taking water away from the roof to a location far from the foundation. The most common gutters are aluminum, and are installed by contractors. Vinyl gutter systems are also available to the homeowner without the specialized tools to deal with the aluminum gutters. Other gutter systems are made of tin, copper or wood.

If water is still collecting near the foundation, drain extensions (above or below ground) can be added to draw the water away from the house. Another low budget fix is to raise the soil level near the foundation, so that the land slopes away from the house, and not into the house.

Gutters need to be maintained by:

1. Cleaning out leaves and debris regularly (or add leaf guards to the gutters)
2. Cleaning downspouts regularly
3. Checking for leaks
4. Maintaining gutter supports

 

 

 

Metal roofing

Metal roofs are great for any type of roof and are ideal in forested, moss prone, or heavy precipitation areas. Typically made up of steel, alumninum or copper, metal roofs offer some of the best protection for your home. They withstand high winds, shed snow and rain very effectively and are fire resisitant. Some people fear that hail may put dents in a metal roof, but many roof metal materials guarantee no denting. Another concern is that lightning may be attracted to a metal roof, and is more likely to strike the house but this is unfounded.

Metal roofs are very lightweight, weighing about one quarter as much as tile roofs and nearly half as much as asphalt shingles. Metal roofing is generally more expensive than asphalt roofing, but cheaper than tile or slate roofing. It has a long life and can even lower heating and cooling costs because it reflects heat from the sun. If properly installed a metal roof will usually last as long as the house with manufacturer warranties often lasting 50 years. Although metal roofs can be walked on, care should be taken when walking on a roof with deep shake and tile profiles, to prevent damage to the contour of the ridges.

Metal roofs vary in color, style, and texture more than any other roofing material. They can be made to look like wood shakes, standard shingles, or even tile but without the extra weight. Many styles come in sheets which are quickly and easily installed while metal shingles will require additional time and expense because of individual placement and nailing. Recycled metal roofing can also be purchased, as an environmentally safe option for your home.

Pros:

• Long life
• Long warranty
• Good weather resistence
• Available in a variety of shapes and colors
• Enviornmentally Friendly

Cons:

• Material expense

 

EPDM & PVC Roofing

EPDM rubber roofing

The ethylene propylene diene monomer (EPDM) creates a single layer rubberized roof that is long lasting and UV resistant. EPDM roofing systems do not require a mineral coating, which makes them much lighter than tar and gravel roofs. It should be noted that a rigid insulation is recommended for this type of roof.

Pros:

• Energy Efficient
• Can be used with a wide variety of roof shapes
• Cleaner application than many low slope options
• Performs well in high wind and hail
• Good long-term performance for a low slope roof

Cons:

• Not intended for high rain or snow areas

PVC membrane roofing systems

PVC membrane is a roof membrane composed of only one layer of material, polyvinyl chloride. PVC roofs are specially designed to withstand ponding water- PVC membrane is welded together with hot air (no open flame) to eliminate all seams so moisture can not pass through. PVC roofing systems also reflect nearly 90% of the heat of the sun, thus lowering energy costs substantially, especially in high-heat areas such as the southwestern United States.

Pros:

• Fire safe material
• Energy Efficient
• Good weather resistance
• Good long-term performance for a low slope roof

Cons:

• Not intended for high rain or snow areas

 

Shingles & Shakes Roofing

Cedar shakes

Cedar shakes combine a traditional look with reliable, modern performance. Cedar shakes are a great choice for historic homes or homes in new developments with high appearance standards. Also, cedar shakes are an environmentally friendly option for consumers. The life expectancy of cedar shakes is up to 30 years, if quality materials are used. If the contractor uses commodity materials (low quality) or if the workmanship is poor, the life expectancy can drop to only 10 to 15 years. Another concern potentially associated with cedar shakes is that many communities will require you to install pressure-treated fire retardant shakes, which increases the cost of the materials.

Asphalt (Composition) shingles

Composition shingles are used on the majority of homes in the United States. These shingles are made of a base (organic or fiberglass) that is saturated with asphalt and coated with minerals on one side to resist weathering. The fiberglass shingles are more flexible and stronger than organic shingles. Shingles come in a wide variety of colors. Composition roofs can be overlaid with a new roof if the initial roof is a single layer and in good condition. The life expectancy of composition shingles depends on the rating (e.g., quality) and ranges from 20 to 30 years. Most manufacturers will cover a composition roof under warranty, but only if it has been installed by a certified roofer as the most common problems and maintenance issues occur when the installation did not include adequate ventilation and/or flashing.

Dimensional shingles

Dimensional shingles are very similar to composition shingles, but are thicker, and can be used to create a more custom appearance. Depending on the rating, dimensional shingles also have a much better lifespan, with an expectancy of up to 40 years. The issues and concerns with a dimensional roof are the same as those associated with composition shingles, moss buildup, quality, and adequate venting/flashing.

Both shingles and shakes are used as a siding material and a siding style as well.

 

Slate Roofing

While slate is the most expensive roofing material on the market it is also the most durable and one of the more attractive. Literally cut from slabs of stone slate roof tiles are most commonly grey but do occur in a variety of colors. Prices for slate commonly range from $600-$1000 per square compared to the price of asphalt shingles which is in the $60-$100 per square range. On the upside, slate roofs regularly last over 100 years and in rare occasions have been known to last twice that long!

Slate roofs require little maintenance are very resistant to molding and insects and are fire proof. Slate is a heavy roofing material and can only be used on roofs that properly supported for such weight. Most residential homes would require additional materials and labor to increase the roofs strength, adding to the expense of installing a slate roof. Should your slate roof need to be repaired it is important to have the work done by a roofing contractor experienced with slate. Not only does slate require a certain amount of expertise to install correctly it is a brittle material which can crack and/or break if walked on

The highest quality slate in the U.S. comes from Vermont , with other quality slate materials found in Pennsylvania, or imported from countries such as Spain , China , or Canada. You can also buy synthetic slate, which is made from either a mixture of slate dust and glass fiber resin, or a combination of cement and fiber. Synthetic slate isn't as fragile as real slate, and it maintains many of the same protective qualities.

While slate has historically been a popular roofing material today it is not installed as widely and frequently as in the past. The decline in popularity of slate can largely be tied to the advent of cheaper and easier to install materials, asphalt shingles being chief among them.

Pros:

• Long life
• Long warranty
• Good weather resistence
• Enviornmentally Friendly

Cons:

• Material expense
• Expensive to repair

 

Tar & Gravel, Bitumen and Roll Roofing

Built up roofs are used when the pitch is no more than 3 inches rise to 12 inches run. This roof is installed by alternating layers of heavy roofing felt and hot asphalt or tar. The final product is coated with a mineral such as gravel. Built-up roofs are rated by how many layers are applied, usually between 3 and 5 layers are considered standard.

Pros:

• Lower cost
• Good weather resistance

Cons:

• Can be messy to install
• Not intended for high rain or snow areas

Modified bitumen roofing

Similar to the tar and gravel roof, this roof adds layers of polyester or fiberglass with bitumen. These additional layers add strength and resistance to a flat roof.

Pros:

• Lower cost
• Good weather resistance

Cons:

• Can be messy to install
• Not intended for high rain or snow areas

Roll roofing

This low cost roofing product is made from materials similar to asphalt shingles, but has a relatively short life expectancy-less than 10 years-because it is a single-ply roof. Roll roofing is commonly known as 90-pound felt, since one roll covering 100 square feet weighs around 90 pounds.

Pros:

• Low cost
• Reasonable weather resistance

Cons:

• Short life
• Not intended for high rain or snow areas

 

Tile Roofing

Clay Tile

Clay tile is most often thought of in the traditional "S" or "Spanish" tile look but clay can now be made in several other patterns as well. Tile is a very resilient material and is able to withstand some of the harshest elements such as hail, wind, and fire. The one drawback to tiles is their weight; they are very heavy, and require certain structural standards for the frame and decking of the roof. They have a great life expectancy, with a minimum duration of 40 to 50 years. Tiles may need to be predrilled and nailed if you have a steep pitch roof, or even supported by metal brackets, all of which could increase the cost associated with this type of roofing system. Tile roofs offer one of the longest warranties in the roofing industry. Most tile manufacturers (both clay and concrete) will offer a minimum of a 50 year limited warranty on their products.

Concrete Tile

Concrete tile has essentially all of the upsides of clay tile but with the added advantage of being available in an even greater number of styles including traditional clay, slate, and even wood shake! It is ideal for communities with appearance codes because it has such a wide range of appearance options.

Pros:

• Long life
• Long warranty
• Strong material
• Available in a variety of shapes and colors
• Environmentally Friendly

Cons:

• Material expense
• A heavy material, which will not work on all roofs

 

Green Roofing Systems

Taking the place of the usual shingles, tiles, metals, and membranes, the green roof is on the rise in popularity, as it proves to be an energy efficient, earth friendly alternative. The green roof covers those traditional roofing materials with vegetation to great benefit. A green roof has a number of layers including a soil layer, as well as layers for drainage and waterproofing with the vegetation layer topping them all. Though it varies between green roof systems, they may even have an irrigation system installed for upkeep of the plants. However the plants typically used on these roof systems do not require much watering, since the installed plants are generally found in drought prone areas.

Green roofs are not only only on the rise here in the United States, but are quite popular in different parts of Europe. In fact, Germany is considered to be at the top of green roof research and development partly due to the German public feeling it a duty to use as little energy as possible.

Irrigation systems aren't necessary under most circumstances, but there are the few exceptions. When installing an irrigation system for your green roof, do not use surface watering systems such as a drip or spray system. You should install a system that delivers the water deep underneath the vegetation and straight to the roots. A drip system wastes water through evaporation, taking away much of the needed water before it can get to the plant roots.

Green roofs come in two different types: extensive and intensive.

First there is the extensive green roof, which is also referred to as an eco-roof. The extensive green roof has fewer and thinner layers, making it much lighter. The lighter roof requires less additional bracing and support for the structure, thus making the extensive roof cheaper as well. Since they have less soil medium, extensive roofs plant selection is limited to mosses, succulents and grasses, and do not grow to be real tall. These plants have an ideal height of between 16 and 24 inches and is why these roofs are often called low profile. The extensive green roof is very low maintenance since most the plants are tolerant to a drought.

Intensive green roof isn't as limited to the variety of plants usable because the soil medium is increased greatly. But because of this, an intensive roof will be much heavier, and may require additional bracing and support. But due to the increased soil, plants will typically be taller among intensive green roofs, and require a lot more maintenance. It is also not unheard of to find waterfalls, gazebos, and other small structures atop an intensive green roof.

There are a number of advantages to having a green roof:

• A green roof reduces a lot of heat from the roofs survace, thus saving on air conditioning and energy costs for the building. This is especially good in urban areas with big buildings because those large structures create what is called a heat island affect, making the inner city substantially hotter than surrounding areas.
  
  
• A green roof works as a good sound insulator, reducing the noise inside a building by up to 10 decibels.
  
  
• A g reen roof shields the roof membrane layer from getting heat and sun, thus making the membrane last longer. Green roofs also do very well retaining water, causing less storm water drainage, and run off from the building.
  
  
• Green roofs reduce the amount of water pollutants that run off with rain water from buildings. The Green roof retains much of the water in the soil and the plants will actually absorb some o the pollutants.
  
  
• Green roofs also act as a natural air filter. The vegetation will absorb various airborne toxins, purifying the air.

Conclusions

Although green roofs are initially more expensive to install, they can save you time and money in the long run and are good for the enviornment as well. For more information on green roofs check out the International Green Roof Association