Things you need to know before you decide

A typical homeowner has very little idea what they are getting into, and what to expect from their roofing contractor.  We have tried to put some information together to guide you through the process so that you should be able to make an informed decision.

You should have a general idea about your roof and your roofing needs by the time you get to the end of this guide.

What is a roofing pitch? How does that affect you?

As shown in picture you can simply look at your house and have a general idea of  how steep the roof for your house is. It varies between 1/12 to 18/12 or even more.

Now the question is, why a homeowner should bother about the roof pitch. You  need to know this because it affects the total cost of replacing the roof.

It is also  important as the pitch dictates what type of roofing system would be ideal for the house.

A typical house with a pitch less than 7/12 has a greater risk of an ice dam than a house with a greater pitch value. Steep roofs with pitch higher than 8/12 take more labour  time, which consequently increases the overall cost.

What is the Ice Dam?

Ice dams are formed when melting ice sits at the very edge of the roof and causes the water to get under the roof as shown in picture. Ice dams happen in the late winter months in general.


It’s a thin rubberized asphalt membrane that goes beneath the shingles of your roof. There is a plastic paper on the backside which is peeled off so that it can stick to the plywood decking. As the name implies this membrane acts as a shield to your roof when you have an ice dam buildup. Typically, it only covers the first 3 feet of the roof starting from the edge.


An Ice and water shield is not a must for every roof and is certainly not required on all slopes of the roof. We recommend using ice and water shield for all the roof edges where the slope of the roof is less than 8/12.
We use the ice and water shield at the critical places at your roof such as the valleys, chimneys etc. regardless of the pitch of the roof.

What are the underlayments?

Underlayment is a form of a barrier that is used under the shingles as an extra protection. It is typically applied after the ice and water shield with only 3 inch overlap. First 3 feet of the roof is covered by the ice and water shield and the rest of the roof is covered by the underlayment.

There are different types of underlayments in the market but the two most commonly used are:  

1.Felt paper

It is a traditional type of underlayment which was very common back in the day. Felt paper is not water resistant or waterproof, that is why we no longer use it in our projects. Some companies still use this as a protection because it is very cost effective as compared to synthetic underlayment.

2.Synthetic underlayment

This is a new type of underlayment created by weaving together polypropylene or polyethylene and a polymer to form an all-over protective barrier. It is water resistant and most commonly used these days.

When do you need an underlayment?

Some amount of air is always trapped under the shingles, which produces  moisture in between the shingles and decking during varying temperatures.  Synthetic underlayment prevents that moisture from causing mold on the  decking plywood.

It is also effective in case of an ice dam. Same as ice and  water shield, underlayment is also an optional layer of protection for the roof.  Even though it is not required to have it for every roof, we recommend using  it for roofing slopes upto 7/12. We do not recommend underlayments for pitch higher than 8/12 to reduce unnecessary cost to you.

Metal roof edge/drip edge. Do you need it?

Roof edge or drip edge is a piece of metal installed at the very edge of the roof before applying any type of membrane on the decking. The basic purpose of  the roof edge is to prevent any water from touching the decking or even  getting in between the facia and the eavestrough.

Metal roof edge is only required if there is a gap between the decking and the trough, or the eavestrough is installed too low. There is no need for a metal roof edge in most new build houses. You do not have to worry about whether you need the metal roof edge or not as we will recommend it if you need it.

Open (Metal) valley vs Closed valley

A valley is where two slopes meet up. There are basically two ways to install shingles in a valley, Keeping the valley open by installing metal in the middle or closing it after using an ice and water shield under it.

None of the valleys is better than the other. The type of the valley to be used is based on the design of the roof. Open valleys are the best when the meeting sides have the exact same slope.
On the other hand, it is always a good idea to close the valley when one side has a pitch value far higher than the other, for example if two meeting sides are 9/12 and 6/12, it is best to close the valley to prevent water from getting underneath during ice dams. We may use either type of valley as required by the roof design.

Air Vents

Vents are cut through the roof decking to provide proper flow of air out of the attic. There are a number of ways to ventilate the roof by using different types of vents. According to the Ontario building code, one vent of 8×8 inch is required for every 300 sq. feet of the attic space. Some of the most commonly used vents are as follows:

1.Duraflo 6050 Plastic Vents:

These are very widely used vents because they are highly durable as well as cost effective. In some cases when there is a risk of wildlife infiltration, we recommend using metal vents instead of plastic ones.


Air hawk metal vents are solid enough to protect your roof from any wild life attack. We recommend using these especially for single story houses and when there are trees close to the roof. We have seen animals get into the roof by chewing through the plastic vents.

3.Max Vents:

Max vents are bigger in size and they are much more effective. They have a unique design which helps suck the air out of the attic. One max vent can cover up to 1200 square foot of attic space. Max vents can not be used in combination with any other type of vents.

4.Power vents:

These are very effective for low slope houses when there is very little attic space. These vents are power operated to  force the air out of the attic. These are  also used when one side or some  specific area of the roof stays warmer  than the other places.

5.Turbine vents:

These vents were very common a few years ago but not anymore. They tend to break down during the wind storms and they also start making noises only after a few years. That is the reason why we do not recommend these vents anymore.

6.Ridge vent:

Ridge vent is installed by cutting the decking at the very top. This  type of vent is best to prevent any air being trapped at the top of the attic and  preventing any moisture build up.

Exhaust vents

These are the vents installed on the roof for exhaust flow from the washroom or kitchen etc. An insulated duct pipe is connected from the washroom fan to the exhaust vent in the roof. They are smaller in size to  match the size of the exit pipe.

Some of the most commonly used exhaust vent are as follows:

1.Duraflo Plastic Exhaust vent:

These vents are cost effective and highly durable vents. They have a built in plastic mesh at the face to keep leaves etc. from going in and blocking the pipe. They also have a flap inside to open and close with the flow of the air from inside.

2.Metal Exhaust vent:

As the name suggests, these vents are made from metal. These vents have the similar features and functions as the plastic ones except they provide better protection against rodents etc.

3.MAX CT4 Exhaust vent

These vents are high quality vents made from thick metal. They are a little bigger in size and made in such a way that they provide protection from leaks during snow build ups around the vents.

Plumbing Stack flashing

The flashing is used to flash around the plumbing pipes sticking out of the roof. The rubber around the hole makes a perfect seal around the pipe and keeps the water out. We only use Duraflow products as they are the most durable ones available in the market.

What are the wall Flashings, Should they be replaced?

Wall Flashings are also known as counter flashings. These are used at the transition point where shingles meet a wall, chimney etc. These are metal pieces typically made from 29 gauge pre painted galvanized steel.

Wall flashings have a longer lifespan than shingles, so it is not always required to replace them. Typically it is not necessary to replace flashings if the house is not older than 20 years. We always leave this decision to the homeowner whether they want to spend a bit extra to get new flashing at the same time as the roof.

Insulation, How do I know if I have enough?

It is essential to have enough insulation inside the attic to prevent any issues. Some of the common problems that happen due to the lack of insulation are high utility bills, moisture build up etc. It is recommended by the Ontario Building Code to have between R50 to R60, which means having between 15 to 22 inches of insulation.

You can simply walk into the attic and measure the insulation thickness of your house, but you should always be careful not to step on the drywall and cause damage. Alternatively, you can call us to provide you a free inspection to find out whether you need insulation or not.


We have created this guide to provide you with some basic information about the roof. The information provided in this guide is solely based on our own experience and knowledge. We always recommend that homeowners do their own research before making any decisions.

Real Blue Roofing Services Inc. shall not be held liable for any damage or loss to the homeowner in any case.