How to Replace Your Roof

All homes need to have their roofs replaced from time to time. There are major differences in materials and installation that will dramatically affect the price and longevity of them. Today we would like to focus on the most common material in our area, asphalt shingles.


When selecting a roof with 3/12 pitch or greater, asphalt shingles are economical;

These shingles will perform well for many years when properly installed by a licensed contractor who specializes in asphalt shingle roofs.


In order to get the best price and value from a roof, we have some tips you should consider, when reviewing a contractors quotation.


1) Does the bid include tearing off the old roof, or is it a roof over?

2) What kind of shingle are they using, is it a Laminated Shingle (also called Architectural Shingles)  – 30 years or more, or standard 3-tab shingles (cheaper 15+ year material)?

3) Are there any sheathing repairs in the bid? What material?

4) Bids should include all new flashing, (chimney to roof, siding to roof, skylights, plumbing and vents stacks)

5) Ensure that your contractor will bring your roof up to current standards for ventilation. (1sf of vent for every 150sf of roofing) We see many homes with inadequate roof venting.

6) Assure all bath and kitchen vents are properly vented with dedicated vents for each fan and do not point vent hoses to attic vents.

7) Including zinc strips will dramatically reduce moss problems on your new roof.


Asphalt Shingle Installation

Asphalt Shingle Installation


Occasionally, home owners will try to save money by ‘roofing over’ an existing roof. This is not usually recommended. A roof that is installed over an old roof will not lay flat, beside other issues. Why would anyone cover up old, deteriorated, damaged, roof covering material after spending all that time and money? Worse yet, what are the current conditions of the underlayment and plywood sheathing that has been covered up?

This can cause the new roof to not perform as well, leading to premature leaks and failure. It also traps more heat, causing the tar in the roof to evaporate petroleum, leading to cracks and failure. In addition, the added weight of another layer can cause structural problems.


As the surest way of knowing, the safest thing to do is to have the roof stripped so that it can be examined for potential structural problems and what the conditions are before resurfacing it and to be sure that you are acquiring a professional roofer that knows what he is doing.


When your roof is replaced, we recommend you choose a 30-year, architectural shingle. Standard 3-tab has a much shorter life, (closer to 15 years). Since the cost of a roof is mostly labour, there is no reason to go for the cheap materials. The labour is the same, and the materials cost about 1/3 more. With double the lifespan, it is the best value for your money.


When getting prices, ask the roofing companies if their bids include any sheeting repairs. Most tear-offs will require some repairs to sheeting. There are two kinds of common products, OSB and plywood. OSB is the standard sheeting used today, but plywood is a more expensive and superior product.

Ventilation is key to a long a lasting roof. When ventilation is poor, it is much more likely to have problems with structural pests in the roof framing and mold in the attic.


A cheap roofing bid will often not include proper venting of bath and kitchen fans.

When these are not properly vented outside, the moisture from them will contribute to structural pest issues and cause the roof sheeting to rot prematurely. Zinc strips will help keep moss from taking over your new roof. This will cost more upfront, but moss will destroy roofs quickly in wet climates.

About the Author DavidFairbairn

Author David Fairbairn is a certified, licensed home inspector serving Vancouver and the Lower Mainland. He has been featured in the media and has contributed to "24" Newspaper, and Global TV. He has spent years working with residential and commercial building projects, and holds a Power Engineering License in BC. Why not give him a call for your next Home Inspection? Call 604 395-2795 or email today!

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