Roof Replacement Basics

According to Maslow's Hierarchy, 'safety needs' come right after basic physiological needs such as breathing, eating, and drinking. Well, having a leak-free roof that isn't going to cave in on you is one of those 'safety needs' (i.e. shelter from the elements). And, within the category of home renovations, your roof should ALWAYS be at the top of your list. Updating a kitchen is always nice, but a leaky roof is a disaster waiting to happen. Here's a few key points about roof replacement to help you make a more informed decision on when to (or when not to) replace your roof.

Picture: modified bitumen roof replacement in progress

Home Renovations: Roof First, Interior Next

Your roof should be at the top of your list of home renovations. Why? Well, a leaky roof can allow massive interior damage. So there's no point spending a fortune on interior renovations if your roof is falling apart. A good roof will protect any investment you make on the interior of your home, so it's a great place to start when updating and remodeling.

Don't Replace Your Roof When

There's really only a few scenarios when you don't need to worry about replacing your roof. 1-the roof is in good condition, and 2-you're going to demolish the whole home. A possible third condition is if your roof does need to be replaced but you are just stripping apart the interior of a soon-to-be remodeled home. Although, once you start constructing and remodeling, you should always invest in first replacing an old roof before you invest heavily in interior construction.

Picture: a recently installed Built Up Roof (BUR), in excellent condition. This roof is clean, with no patches or repairs yet, or any type of visible damage.

What Materials to Use (When Replacing a Roof)

Depending on your local HOA requirements, or city zoning laws, there may be some limitations or requirements on roof choices. Regulations aside, the final decision will involve the structure of your building (slope, flat, other), how much you're willing to spend, how long you want the roof to last, and your personal preference. Usually, although not always, a more expensive roof will last much longer than a cheap roof. Materials such as SPF Foam Roofs or Sea Green Shale can easily last the life of a building (and beyond), but both can be more expensive than more typical and poorer quality solutions.

What Does it Cost To Replace a Roof

A few key factors will drive the cost of replacing your roof. First, does the old roof need to be torn off or can the new roof overlay the existing substrate. This decision must be based on whether you already have existing multiple layers of roofing under your current roof (this is very common with Tar & Gravel). Materials such as SPF foam roofing are lightweight and can usually just go over existing roof materials.

The next two factors in determining the cost of your roof are the square footage and obstructions on your roof. How difficult will it be to install your new roof? Do you have pipes, skylights, AC units, duct-work, solar pipes, or an unusually high number of vents and protrusions? The same size job may vary in cost due to the high number of, or lack of roof obstructions.

The final factors that will determine the cost of your roof are the type of replacement roofing and the material costs. Whether you choose shale, shake, shingles, metal, tile, torch down, modified bitumen, spf foam, tar & gravel, epdm, rubber or other--the cost of the material, and the labor hours and equipment needed to perform the installation will all come into play. The costs of slope / pitch roof replacement range from extremely cheap with asphalt shingles to very expensive with slate or architectural shingles. On a flat roof, single ply roofing is extremely cheap, while SPF foam roofing is possibly the most expensive.

SPF Foam Roofing has taken the lead with the highest quality flat roof replacement. A properly installed foam roof lasts the life of a building, corrects ponding, is leak free, insulates, and protects. The only drawbacks are that foam must be sprayed in warm weather for best results, it can be slightly more expensive, and a highly trained applicator is needed for best results.


The cheapest materials and smallest roof replacement jobs start perhaps as low as $5,000. The average roof, at least in the Bay Area (California) is somewhere around 2,000 square feet. If your roof is 3,500 square feet or more, of course due to additional labor and materials, your cost will most likely be proportionately higher. Expect to pay more for your roof in more expensive areas, such as NYC, San Francisco, or LA. These heavy populated areas are more expensive to live in, so employers must pay more for labor costs and warehousing expenses. Of course you can negotiate with multiple roofing contractors and try to find the lowest price. However, I would strongly advice against choosing a contractor based on price. I would FIRST choose the best contractor and THEN attempt to get a good price from them. If you're unable to afford working with them, then you could try and work with the second contractor. It's best to find a contractor with a clean track record, good stating with the BBB and current licenses, and good references.

Roof Replacement Terminology

Don't be confused if your contractor uses the term "square". This unit of measure is equal to 100 square feet. So a 2,000 square foot home is just 20 squares.

When to Replace Your Roof

You may not need to wait for any particular weather to replace your roof. Generally, the substrate must be dry or the roof will leak after installed. Contractors often have ways of completing roof replacements during narrow time windows or drying the surface of a roof, even in the wettest of outside conditions. I have seen an SPF contractor use plastic and torches to install a foam roof system during light rain (the need was urgent, and the customer had major roof leaks causing internal home damage). So whether your in the middle of summer or the dead of winter, it's best to ask a roof contractor if it's a good time to install your roof or not. The types of materials used, and the pitch of your roof will play a big role in whether or not its an acceptable time to perform a roof replacement.

Picture: Renovations should always start with your roof, to best protect your investment

How Long Roof Replacement Takes

Most traditional roofing jobs, with average size homes probably take 3-4 days. However, I have seen large professional crews that can install a foam roof on a 10,000 or 20,000 square foot warehouse in a single day. Labor hours and roof obstructions come into play here. If your roof is full of pipes, skylights, and ductwork, it could take longer than normal to complete your roof installation.

Steps for Replacing a Flat Roof with a Superior Foam Roof System

1-Prepare: clean off the old substrate, remove dirt and rocks if it was tar and gravel, or pressure wash if the roof is rubber. Depending on the condition of underlying roof, the old substrate may be torn off.
2-Install Sprayed Foam: Spray foam is applied in layers which form a single monolithic barrier to the elements. Foam rises and is 'walkable' after about 1 minute.
3-Spray Protective Coating: A basecoat is applied, then followed by a topcoat of elastomeric acrylic coating. This special coating is designed to stretch a little like rubber, to prevent cracking. The coating creates a reflective energy star approved cool roof coating (counteracts the urban heat island effect), and also extends the life of the foam by protecting it from ultraviolet light emitted by the sun.

Steps for Re-Roofing a Shingle Roof

1-Prepare: All existing shingles are removed and minor repairs are made as needed, and dry-rot or bad wood is replaced with new wood (.e.g plywood, or other). A protective plastic membrane is then installed to seal lower areas of the roof and protect them from ice dams and water seepage.
2-Install Shingles: Asphalt paper and shingles are applied, starting from lowest points of the roof, working up the slope.
3-Install Flashing and Ridge Vent: Metal flashing is installed in high leak risk areas, such as the chimney, vents, or other roof protrusions. Finally, the ridge vent is applied, completing the installation

The concept of maintaining your roof first, then working on your interior upgrades next is an excellent one. Why spend thousands of dollars and hundreds of hours remodeling just to have your work destroyed by water seeping into your drywall, or wood floors -- which could destroy your work literally overnight.

Selecting the Right Contractor

I also think it's really important to select a good contractor to do the work. Doing all the home work is difficult, but it can really pay off in the long run. You need a contractor who can be recommended by both old and new customers, and if they are promising a long warranty, such as 10 years, make sure they have been in business at least 20 years. Also, if they have a website they should be posting their Contractors State License number. You can usually check their license number online and see if they are in good standing. In California, the website is: http://www.cslb.ca.gov/

There are many other good ratings organizations that can help you determine whether a contractor is trustworthy. Some of these are: valuestar, diamond certified, the eichler network, and the better business bureau (bbb). If you're getting multiple bits of work done, such as installing solar and an SPF foam roof, you can also look to see if there's any contractors in your area that can do both. This way, if the roof leaks, or theres a problem, you wont have to deal with multiple contractors all pointing the finger elsewhere.

we must need good roof for home.It has a quality material, proper finishing. proper slope then we decide the life of roofing. if you use good material but not giving proper slope then its been fast damage.

Roofing wrote:we must need good roof for home.It has a quality material, proper finishing. proper slope then we decide the life of roofing. if you use good material but not giving proper slope then its been fast damage.

I agree. The roof is in many ways, the most important structure in a home. To be an effective 'shelter' to the elements, a roof must withstand snow, rain, and other forms of weather while keeping the occupants dry and warm. If a roof fails, the destruction in a home can be devastating. Wood floors, sheetrock, carpets and other interior materials are generally not capable of resisting moisture well. A home inundated with leaks will quickly deteriorate. This is why many experts suggest that a roof is first updated before major interior restoration work is done in a home.

roofsynergy wrote:The concept of maintaining your roof first, then working on your interior upgrades next is an excellent one.

I've always supported this thought. What I think is, security comes first. You don't need to do an interior if your roof or any part of the house is damaged or need to be replaced. Interiors are good but only when you have extra money in your hands and you don't need to repair or install any new part in your house. Roof maintenance is really an important point to remember in the mind always.

I agree as well.