Familiarize yourself with the elements of your roof and the language of roofing.
Get several bids for any major roofing job. Prices different companies
quote for the same work often vary by 100 percent, which may represent
thousands of dollars.
Use estimators as your consultants, getting feedback from them to determine
exactly what needs to be done. Then go back to them with the final description
of what you want and invite them to bid on the work.
Use our ratings of area roofing contractors, which appear on our Ratings Tables, to find high-quality companies.
Before using any contractor, ask for proof that it is licensed and carries
liability and workers compensation insurance.
Get a copy of the warranty from the manufacturer of whatever roofing materials
are used. Also, get a warranty on the roofers work, ideally for five years
or more; have the roofer write into your contract: In addition to all
other warranties, if roof leaks within five years [or, better still, 10
years], except as a result of accidental damage, contractor will bear the
cost of labor and materials to eliminate all leaks.
Get a fixed-price contract. Specify using pictures or in words exactly
what roof areas are to be covered. Specify other details, such as whether
old shingles are to be removed, whether flashings are to be replaced, who
is responsible for cleaning up and hauling away debris, and exactly what
types and weights of materials are to be used.
Arrange to pay for the work as late in the process as possible. About half
of the contractors we surveyed will allow customers to withhold all payments
until the job is complete. Try to arrange to withhold at least a portion
of the price until your roof has been tested by stormy weather.
The high prices of many home improvement jobs are often tempered by the
rewards they provide. A room addition or finished basement provides more
living space. A new kitchen may inspire you to cook and entertain. New
carpet, flooring, furniture, or a new coat of paint improves aesthetics.
But unless youve let the old one deteriorate to the point where you have
buckets strewn about the house, a new roof wont make your life seem better.
Your wallet, however, will feel the difference. Roofing work is expensive,
and, unless you purchase carefully, you may spend thousands of more-than-necessary
dollars to get less-than-satisfactory results.
Our Ratings Tables include ratings of local roofing contractors. The
table shows which areas they serve and which of the major types of roofs
they work on.
The ratings of area roofers from our surveys of consumers (primarily CHECKBOOK
and Consumer Reports subscribers), shown on our Ratings Tables, let
you check the opinions of more than 2,000 of your neighbors on area roofers.
(Our customer survey and other research methods are further described here.)
Our survey asked consumers to rate roofers they had used inferior, adequate,
or superior on the following questions: doing work properly on the first
try, starting and completing work promptly, letting you know cost early,
advice on service options and costs, and overall quality. For companies
that received 10 or more ratings, our Ratings Tables report the percent
of each companys surveyed customers who rated it superior (as opposed
to inferior or adequate) on each of these questions. Our Ratings Tables also report the percent who rated each company adequate or superior
(as opposed to inferior) for overall quality.
A number of the roofing outfits on our Ratings Tables were reviewed
very favorably by a high percentage of their customers. At the time of
our last full, published article, 42 of the 79 companies were rated adequate
or superior overall by 95 percent or more of their surveyed customers;
22 were actually rated superior overall by 90 percent or more of their
surveyed customers. Unfortunately, however, substantial numbers of the
customers of some of the outfits listed on our Ratings Tables regretted
their choices: six of the companies were rated inferior overall by at
least 20 percent of their surveyed customers.
For firms that were evaluated in our last full, published article, our
Ratings Tables also show counts of complaints we gathered from local
Better Business Bureaus (BBB) for a recent three-year period and complaint
rates relative to the volume of work companies do. For more information
on reported complaint counts and rates, click here.
One way to reduce the risk of being dissatisfied is to arrange to pay for
most or all of the work only after the job is completed. In California,
a roofer cannot require a down payment of more than the lesser of 10 percent
or $1,000, but home improvement contracts can require payment of larger
portions of the contract once work begins. Withholding additional paymentsor
all paymentsuntil work is completed gives you leverage to ensure that
work is done properly and on time. Our Ratings Tables show the percentage
of the contract price on a $5,000 roof installation job each company ordinarily
allows the customer to pay at completion or later. About half of the companies
allow you to withhold the entire amount until completion, but some require
customers to pay at least half earlier.
Think ahead about obtaining additional leverage in case youre dissatisfied
with a contractors performance. A company may seem conscientious and cooperative
early in the process, but prove harder to live with later.
By choosing a contractor that is licensed, the threat of license cancellation
represents one form of leverage in working to resolve disputes. And because
you have taken the care to choose a licensed contractor, the licensing
authorities will feel you deserve their help. Ask any contractor you are
seriously considering to present proof of a currently valid license; then
verify by calling the Contractors State License Board (CSLB) at 800-321-2752
or by checking the CSLB website at www.cslb.ca.gov. In California,
any roofing job that costs $500 or more must be performed by a licensed
An additional advantage is that if a licensed contractor fails to perform
under your contract, you can seek compensation through the CSLB complaint
process. One condition for obtaining a license is that the contractor must
maintain a bond of $12,500. If CSLB inspectors find that a customer is
due money back from a roofing contractor, the contractor can be ordered
to pay; if the contractor fails to pay, its license can be suspended or
revoked and the customer can make a claim against the bonding company.
There is a statute of limitations on complaints to the CSLB: four years
from the time of the work in the case of patent (easily discoverable) defects;
10 years for latent (not easily discoverable) defects. You generally must
file your complaint within these time limits for the CSLB to act on your
behalf. But if a contractor provides a workmanship warranty for a period
longer than specified in the statute of limitations, you can press your
claim through the CSLB for the full period of the warranty.
A $12,500 bond should cover the costs of most individual roofing jobs.
But if a company has gone bankrupt, other customers are likely to have
filed claims, and the bonding companys total liability is limited to the
amount of the bond. Wages of company workers will be paid first; then the
bonding company will divide the remaining funds among all claimants, prorated
according to the amount of their claims.
If a third party is injured by a contractor working on your home, or if
one of the contractors employees is injured, you could be liable. The
best way to protect yourself is to make sure the contractor carries liability
and workers compensation insurance. Before signing a contract, require
the contractor to show you current certificates of insurance for both
liability and workers compensation; insurance companies readily issue
such certificates. Alternatively, ask the contractor to provide contact
information for its insurance agent so you can verify that the contractors
policies are up-to-date.
You need to make sure your roofer will be around to finish the job and
that you wont be left fending off the roofers creditors who wish to place
a lien on your house.
A good way to assess financial soundness is to obtainand checkreferences.
Ask for the names of major materials suppliers. Then ask suppliers about
how much credit they commonly extend and the contractors recent payment
If your roof has been damaged during a storm, be wary of contractors who
appear out of nowhere to offer help. Scads of roofers make their livings
chasing stormstraveling from area to area in search of easy-to-obtain
business. Some of these companies perform good work, but many do not, and
if your newly repaired roof begins to leak a year or two later, it could
be hard to track down the out-of-area contractor.
You may get two types of warranties on roofing work: a warranty on materials
from the manufacturer and a warranty on workmanship from the roofer. Many
manufacturers also offer extended warranty protection.
The materials warranties offered by the major shingle manufacturers are
very similar. Asphalt composite shingle manufacturers, for example, agree
to pay for the costincluding laborto repair or replace shingles proven
to be defective. The duration of the warranty varies with the quality
of shingles. A manufacturers warranty generally begins with a specified
period of time (for example, five years) during which the warranty covers
the entire cost of replacing defective shingles. After the initial period,
the manufacturers exposure is reduced on a pro-rata basis each year for
the remainder of the warrantys duration.
Roofers warranties of their labor may not be spelled out as clearly. Some
simply say labor guaranteed for X year(s). Others say guaranteed against
defects in workmanship for X year(s). Its not clear whether these statements
mean you will recover costs or have work redone for free only if you can
prove that the work was done improperly, or whether you only have to show
that the roof leaks. Its also unclear whether, if the workmanship is defective,
the contractor must provide only labor or also required materials.
Youll be better protected if the roofer lets you write into your contract,
in addition to all other warranties: If roof leaks within X year(s), except
as a result of accidental damage, contractor will bear the cost of labor
and materials to eliminate all leaks.
Roofers warranties most often cover one to two years, but some are in
effect for five years or more. Most roofers offer different warranties
for different types of roofs and shorter warranties for repair jobs than
for roof replacements.
To supplement roofers warrantiesand to protect yourself if roofers go
out of business and arent around to honor their warrantiesmost manufacturers
now offer extended warranties that cover workmanship. To buy one of these
warranties, you have to use a contractor that has been approved by the
writer of the warranty, which usually involves checking out proper licensure
and insurance coverage. Also, the warranty seller will require the roof
to be installed according to proper specifications (adequate ventilation,
premium felt paper, ice and water protection at locations of likely leaks,
Extended warranties usually cost $4 to $10 per 100 square feet of the roof,
depending on the length of the warranty. If your roof measures 2,500 square
feet, and a typical 20-year extended warranty costs $10 per 100 square
feet, youd pay $250. As with most extended warranties, CHECKBOOK doubts
that the value of these manufacturer-offered warranties justifies the cost,
but they do represent an additional form of protection.
The quality of a roofers work and its financial responsibility should
be your primary considerations. No price is a bargain price for a roof
that leaks or looks unattractive or is never installed. But once you have
identified roofers that measure up on quality factors, price becomes critical.
Contract to have roofing work done on a fixed-price basis, following an
We worked with nine subscribers to get bids on roofing jobs for their homes.
As much as possible, roofers bid on the same specifications. The roofer-to-roofer
price differences on the same job were striking.
Table 1 includes examples of different bids for these subscribers jobs.
For one job, prices ranged from $5,400 to $20,195a difference of more
than $14,000. For another job, quotes ranged from $5,616 to $13,900a difference
of more than $8,000.
Table 1Some Roofers Charge a Lot More Than Others
The message is obvious: Get several bids.
Get your bids from companies that rate high for quality. Our experience
with roofing bids is that there is no consistency: Contractors, including
high-quality contractors, may charge high prices for some jobs and low
prices for others. There is little price-quality relationship.
Theres no firm rule as to exactly how many bids you should get. You cant
know in advance whether the next bid will be lower than othersit could
save you thousands of dollars or be higher. Likewise with the third bid.
Figure 1, based on multiple bids to replace an average-size asphalt composite
shingle roof, illustrates what you can expect to save by getting additional
The likely gain from a third bid is smaller than the gain from getting
a second bid. Obtaining a fourth bid is usually even less productive. And
while the shape of a curve, like the one in Figure 1, would be different
for different jobs, the likely savings from getting three, four, or more
bids will readily justify the effort.
Figure 1How Much a Typical Consumer Might Expect to Save By Getting More
Than One Bid on a Re-roofing Job
Here are guidelines on getting bids:
Invite out more companies than you really want to see: Some wont show
up for months, if ever. When youve seen enough, call the remaining contractors
and cancel. During some periods, especially after roof-damaging storms,
you may have to invite many contractors to get even a few to appear.
Use estimators as your consultants. Until you get your first few bids,
you probably wont know exactly what work you need. Ask each contractor
for its recommendations and the reasons behind them; then weigh the arguments
and settle on your own set of specifications.
Once you have a tight description of your specifications, ask the contractors
that have already bid on your job to adjust their bids accordingly; give
a copy of the specifications to any additional companies that you wish
You probably wont have to be present when estimators arrive, unless you
need to point out water damage inside your house. If you wont be there,
email your specifications in advance or leave copies of them.
Get more bids on larger jobs. A 20 percent saving on a $500 job is just
$100, but if you can save 20 percent on a $10,000 job, thats $2,000.
Get additional bids if there are large differences between the first two
or three bids.
Get more bids on jobs when labor, rather than materials, comprises a large
portion of costs. Contractors pay roughly the same amount for materials,
but there may be significant differences in their hourly rates for labor
and how much their workers accomplish per hour.
Get more bids if its easyfor example, if youll be home anyway or can
arrange for the roofer to come over while youre gone.
For small repair jobs, some contractors work on a time-and-materials basis.
If possible, avoid this arrangement; youre much safer with a fixed-price
contract. But if you must pay by the hour, ascertain the hourly labor rate,
how many workers it includes, the minimum charge, whether youll be charged
for travel time, and how partial hours are rounded. Youll find that getting
this information is like pulling teeth.
Its not enough to choose a good roofer. To get the roof you want when
you want at the best possible price, you must also deal with contractors
Determine what you need.
Inspect your roof carefully. Does it all need to be entirely replaced,
or are some parts newer and in better shape? Are the gutters in good shape?
How about the flashings? Is there rot in the fascias or sheathing? Is your
attic properly ventilated? You can get free help from each estimator you
consult, as each of them may recommend slightly different remedies. To
shop meaningfully, request estimates on the same work from each company.
But also ask them to propose variances from the basic work plan, the reasons
for these variances, and their effects on the total cost.
Familiarize yourself with the elements of your roof and the language of roofing.
Specify in your contract what you want done.
Estimators proposals are often imprecise, so add specifics before you
sign. For example, for an asphalt composite shingle roof
Specify, using pictures or in words, exactly what roof areas are to be
Indicate whether or not old shingles are to be removed. There are two reasons
for removing old shingles before applying new ones: First, additional layers
may overload underlying sheathing and structural lumberespecially if you
are getting new heavyweight architectural shingles. Second, old shingles
can warp as they dry out and age, causing new shingles to appear uneven.
Consequently, most local codes prohibit application of more than two layers
of shingles, except in unusual circumstances, and roofing over old shingles
is less common than in the past because most manufacturers warranties
dont cover shingles laid over old ones. On the other hand, it costs less
to roof over than to remove old shingles before re-roofing.
If shingles are to be removed, indicate that a new layer of felt must be
applied under the shingles, as required by local codes. Also indicate the
type and weight of the felt.
Specify the types of shingles to be usedtheir make, color, shape, wind
resistance, and weight. Light colors, which tend to absorb less heat from
the sun, may last longer; but theres no hard evidence on how much longer,
and dark shingles may look better on your house. Instead of simple, flat,
three-tab shinglesthe roofing staple for decadesmany homeowners select
architectural or dimensional shingles. These shingles are layered,
cut, and colored to provide more depth and shadow lines, and to more closely
resemble slate or wood shingles or shakes. Examine a sample of the specific
make, color, and style of shingle that the contract specifies.
Specify the warranty on the shingles. Using shingles with a 30-year warranty
rather than a 20-year warranty might cost a little extra but spare you,
or your houses next owner, the cost of labor and materials for roof work
for an extended period (although we have found no scientific evidence that
30-year shingles last significantly longer than 20-year shingles). Architectural
shingles, which are generally heavier than simple three-tab shingles, often
have warranties of 40 years or more.
Indicate which, if any, flashings are to be replaced, which are to be reused,
and what materials are to be used. Unless specified in the contract, a
roofer is not legally required to repair or replace flashings. If you have
copper flashings now, most experts recommend leaving them in place. Aluminum
flashings, on the other hand, are often replaced because they are frailer
than copper and cost less. Specify whether replacements are to be aluminum,
copper, or some other materialand what weight they will be. For copper
flashings, insist on at least 16-ounce (per square foot) material, and
try to get 20-ounce material for valleys. For aluminum flashings, insist
on at least 0.032-inch thickness. The heavier the flashings, the less likely
that they will be damaged during installation or erode away, and the more
likely that they will be reusable in the future. Also specify the width
of flashing, to ensure it will protect the slope and angle covered.
Specify whether any ventilation is to be added. Proper ventilation of your
attic releases the water vapor that rises through your house, reducing
the chance of rot. Also, good ventilation of hot air from your attic during
summer can keep your house cooler. Press roofers to explain their recommendations
regarding ventilation. There is debate within the industry as to how much
ventilation is desirable. Local building codes specify minimum ventilation
requirements. The best approach usually is to put vents in both ridges
and soffits. A good system will include vents that admit cold air under
the entire roof and good insulation above ceilings to keep warm air in
the house from entering any space immediately beneath the roof.
Specify whether the shingles are to be algae-resistant. Growth of algae,
especially in damp and shady areas, can be an eyesore. Shingles can be
manufactured incorporating tiny flecks of zinc or other materials that
retard algae growth. Algae can be treated after the fact by washing down
the roof with readily available chemicalsbut you can avoid all that by
installing algae-resistant shingles.
Specify that the contractor is responsible for a complete cleanup. Nails
and cuttings of flashings are hard to clean up and can be hazardous. Many
contractors use magnetic devices to collect metal. Also request a daily
cleanupso the area wont become a mess over the course of the work, and
you can see early on how well the roofer cleans and be prepared, if necessary,
to supervise carefully. Poor cleanup is a problem cited again and again
by subscribers we survey.
Write in a requirement that the contractor will haul away all debris; otherwise,
you may be stuck with messy piles you have no legal right to force the
contractor to remove. It costs contractors about $100 to haul away shingles
removed from an average-size roof.
Indicate whether metal drip edges are to be installed at the eaves and
the rakes. At about $1 to $2 per linear foot, these edges, which prevent
water from curling back under the shingle edge to reach the wood, are generally
a good investment.
Be similarly specific on other types of roofs. For example, specify the
grade of shakes or shingles to be used on a wood roof, make and composition
of concrete or synthetic shingles or tiles, number of layers and type of
stone for a built-up roof, type and weight of metal and paint for a metal
roof, and materials and application techniques for a modified bitumen or
single-ply flat roof.
Determine if your roof work requires a permit and inspection; if so, specify
in the contract that the company must secure a permit, and that the work
must be inspected and approved before your final payment.
Check with your local building inspection office to determine whether a
permit is necessary for your roof work.
Indicate in the contract when work will begin and how long it will take.
Given frequent customer dissatisfaction with delays (as reflected in our
customer survey findings), you should have the right to get out of a contract
and find another roofer if your original contractor proves too slow.
Spell out a fixed price for the work and a formula for covering contingencies.
While you should be able to obtain a binding contract at the estimate price,
most companies will insist on provisions for extra charges if they will
find damaged fascias, sheathing, or structural lumber. Most of the contracts
state that required carpentry will be performed on a per foot or time
and materials basis. Make sure your contract states how charges will be
computed, typically per-square-foot or per-linear-foot.
Pay for your work as late as possible; indicate payment schedule in the
About half of the roofers we surveyed allow customers to pay nothing until
the entire job is completed. Although companies have standard policies
on payment scheduling, most will alter them to accommodate customers with
good credit standing. In particular, never let your payments get ahead
of the completed work or pay in full until the job is completed. Press
for enough leeway in your payment schedule so that final payment isnt
due until your house experiences stormy weather.
Make sure the contractor carries workers compensation and general liability
Before you sign a contract, ask to see certificates of insurance. If the
insurance documentation is not available when you sign, write into the
contract: Contractor is required to provide homeowner with certificates
of workers compensation insurance and personal liability and property
damage insurance. Work is not to commence, and no payments are required,
before such certificates are provided. In addition, write that you will
be held harmless for any damages which would be covered by general liability
or workers compensation insurance.
Specify in the contract whether subcontractors will be used and, if so,
Write in the contract: No subcontractors other than those listed are authorized
to do work on homeowners premises, contractor is not authorized to give
any other subcontractors access to homeowners premises, and homeowner
is not liable for payment to any other subcontractors.
Arrange to pay for work only after you receive evidence that subcontractors
and suppliers have been paid.
A subcontractor, supplier, or worker may be able to get a lien on your
house if the roofer does not pay for labor or materials used. To protect
against that possibility, write into your contract: Prior to each payment,
contractor must provide homeowner lien releases covering work to which
the payment applies. Each release must state the name of the company or
individual making the release, releasing partys address, materials or
services supplied, amount contractor has paid for these supplies or materials,
and address of homeowners roof, and it must be signed by the releasing
Press for a strong written guarantee.
On asphalt composite shingle roofs, manufacturers guarantees range from
20 years to 50 years. On built-up, modified bitumen, or single-ply flat
roofs, warranties range from less than 15 to more than 25 years. Roofers
guarantees of their workmanship usually run from one to two years, but
you may be able to get one for five or 10 years, or even longer.
If you regret signing a contract, move to cancel it.
If a roofer solicited your business at your home, you are free to cancel
until midnight of the third day after signing. Put your cancellation letter
in writing. It is sufficient to get it in the mail within the three-day
cancellation period, but send it via certified mail with return receipt,
FedEx, UPS, or some other way that generates a record of the date you sent
it and its receipt by the contractor.
If possible, be at home some of the time when the work is being done.
If you are at home, you can detect early any misunderstandings about the
materials to be used and spot gross flaws in workmanship. (See examples
Leave a number where you can be reached.
Things will go more smoothly if your contractor can reach you quickly should
problems arisesuch as damaged sheathing or an unexpected second layer
of old shingles.
If possible, give the roofers access to a toilet, cold drinks, and other
Maintain a file that includes the contract and specifications, any contract
modifications, invoices, canceled checks, and lien releases from subcontractors
and materials suppliers.
If you are not satisfied with your roofers work, complain.
First, negotiate directly with your roofing contractor. If that doesnt
work, complain to the Contractors State License Board (www.cslb.ca.gov
You can save money by inspecting your roof regularly to spot incipient
problems. And you can save by making simple repairs yourself.
You wont save money, however, if you injure yourself or damage your roof.
A few tips
If your roof is steep or made of wood or slate, stay off of it. Theres
just too much risk that you could fall or damage the roof by breaking shingles.
Even if its safe to walk on, stay off your roof as much as possible. It
is easy to crack shingles or pull out nails, particularly if shingles are
warped. Much of the repair work roofers do takes place shortly after new
TV antennas or satellite dishes are installed or removed. Some disreputable
roofers have turned the damage from careless roof-walking to their advantage:
They come out for a minor repair, or offer a free inspection, and advise
that a complete re-roofing job will soon be in order. By walking roughly
on the roof, they ensure that their prophecies are soon fulfilled.
If your roof is safe to walk on, wear soft, rubber-soled shoes such as
tennis shoes. These are best both for the roof and for your own safety.
Dont work on the roof in wet or windy weather. A wet roof or ladder can
be dangerously slippery, and wind can easily knock you off balance. Make
sure you dont have wet grass or mud on your shoes.
Dont put your weight on loose shingles or weak spots through which you
might put your foot.
Make sure neither you nor your ladder touches a power line.
Lift your ladder carefully, and position it properly. Put the bottom end
against the house; from the top end walk toward the house lifting the ladder
over your head until you reach the house and the ladder is upright; then
move the bottom end away from the house about one-fourth of the ladders
length. To make it easier to step off of and onto the ladder, extend the
top of the ladder at least three feet above the edge of the roof. Climb
the ladder by stepping onto the center of each rung, with both hands on
the sides of the ladder. Tie off the ladder to the gutter to prevent it
from being blown over.
When replacing damaged shingles, make sure the newly installed shingles
lay flat over older ones. Also, try not to over-bend existing shingles
that do not need to be replaced. If you bend shingles too much, theyll
crack or split, and you will have to replace them also.
Inspect your roof at least annually and after major storms, even if you
dont notice leaks.
If you have an unfinished attic or crawl space, you can do the most important
work from the inside. Look for evidence that water has come into contact
with the rafters or sheathing. Poke at dark spots to determine if they
are rotten. Examine areas where vent pipes, chimneys, skylights, or other
elements pass through the roof. If you spot a hole in the roof, jam a length
of wire up through it so you can find the hole from the outside.
If you have a finished attic, your task is more difficult. Look for signs
of water damage on the ceiling and walls, but the location of the damage
may be far from the leak that caused it. Water often passes through a leak
and runs along rafters, dripping off only when it hits an irregularity
or obstruction. You can spot problems you cant locate from inside only
with an outdoor inspection.
Begin an outdoor inspection by checking gutters and the foundation area
for fallen shingles. Then look over the roof for missing or damaged shingles
(you may be able to do this from the ground with binoculars). If you see
water damage on an inside ceiling or wall, try to locate the point on the
outside immediately above this damage, and then carefully work back and
forth up the roof looking for the culprit leak. Check that flashings around
chimneys, vents, and other protrusions have not developed holes or pulled
In addition to spotting leaks and water damage, your inspection will reveal
whether the entire roof is due for replacement
A roof of asphalt composite shingles (which may have either a fiberglass
or natural fiber base) needs to be replaced when it has eroded away; first
the granules on the surface disappear and then the shingles themselves
wear down. The first places to wear out are the surfaces below the decorative
cutouts or at the ends of shingles. When holes have eroded through the
shingles, abundant leaks are imminent. Although asphalt composite shingle
roofs typically last more than 20 years, a roof can last less than 15 or
more than 50 years depending on how hot the roof gets, the quality of the
original roofing materials, and other factors. Even before holes appear,
your roof is on its last legs if shingles appear gray and bloated, and
if a piece of shingle crumbles easily between your fingers.
Wood shake or shingle roofs may go bad from drying out and splitting or
warping. As shingles curl, they pull out nails and blow away. When you
begin to lose shingles, it may be time for a new roof. Wood shake or shingle
roofs occasionally last as long as 50 years, but can fail much faster if
located in a shady area where dampness, rather than drying out, is the
problem. Under these circumstances, you may need to have a roofer treat
your roof with a preservative spray every three to five years. It is not
uncommon for roofs that cannot dry between rains to become mossy and rotted
within 10 years.
Tile or slate roofs can last indefinitely (though individual pieces may
have to be replaced).
Metal roofs need to be replaced when they become riddled with holes too
difficult to patch; if maintained properly, they, like high-quality slate
and tile roofs, should last indefinitely.
Built-up roofs (composed of layers of hot bitumen and roofing felt, usually
topped with stone) need to be replaced when they become so dried up and
cracked that multiple leaks develop. Other telltale signs are blisters
and places where the layers have delaminated. A four-ply built-up roof
should last 20 years or more.
Problems with single-ply and modified bitumen roofs usually occur at seams
and around drains. Look for separation at seams and bubbling or cratering
of the membrane. Single-ply and modified bitumen roofs should last 20 years
If you discover a leak, you can easily apply a temporary remedy.
One option is an emergency patch using roofing cement, available from most
hardware stores. Apply the compound generously to the roof surface, even
if it is still wet.
Another option for shingle roofs is to slide a piece of galvanized steel,
copper, or aluminum under the shingle above the location of a leak. The
piece of metal should be large enough to cover the leaking area so that
water will be carried away from the leak.
There are also permanent repairs that some homeowners can comfortably make.
If you find loose asphalt composite shingles, remove the loose nails, drive
in new nails, and cover the old holes and the heads of the new nails with
roofing cement. If asphalt composite shingles are merely warped, hold them
flat with a spot of roofing cement about the size of a quarter.
Replacing a shingle, if necessary, is more difficult. Very carefully lift
the shingles that lie over the bad shingle, remove the nails holding the
bad shingle, remove the shingle, insert a new one, and replace the nails.
If there is a small defect at a bubble in a built-up roof, you may be able
to repair it by slitting the bubble, cleaning out under the bubble with
a trowel or putty knife, sliding cement in under the bubble, pushing the
bubble down, driving in a row of nails on each side of the slit, and then
covering the area with a layer of cement, a layer of roofing felt nailed
around the edges, and a second layer of cement.
For a larger defect in a built-up roof, the procedure is more difficult.
Cut out a square of roofing material containing the defect. Cut out the
area one layer at a time, with each deeper square smaller than the one
above. Then cut new squares of felt to fit and put them in place, starting
with a layer of cement and alternating cement and felt until you have replaced
each layer. Drive nails around the perimeter of the top patch; then apply
another layer of cement, another larger piece of felt to cover the whole
area, and finally one more layer of cement.
Small holes in tin or galvanized steel roofs can be patched with a spot
of solder. Larger defective areas in these roofs can be patched with a
square of tin soldered around the edges or with a piece of canvas. If canvas
is used, apply a coat of paint as adhesive, then the patch of canvas, and
then two or three more layers of paint.
For small holes in aluminum roofs, use aluminum-pigmented caulking compound.
Larger holes (one inch or more) can be patched with a piece of aluminum.
Coat the patch with the aluminum-pigmented caulking compound, and hold
it in place with sheet metal screws coated in caulking.
Many cracks in flashing can be repaired, temporarily at least, with a layer
of roofing cement. Cement can also be used to fill small joints where flashing
has pulled loose from a chimney; simply scrape out the old mortar or cement,
put the flashing back in place, and fill the joint with cement.
Moss and Algae Damage
Moss or algae growth can be a problem for some roofs, particularly wood
shingle roofs. When moss or algae grows on a roof, it holds in moisture
and can cause shingles to rot. Moss also can work down to the sheathing,
causing structural deterioration. You can remove moss or algae growth by
applying a commercial cleaner with a garden hose and/or by using a power
Homeowners who feel comfortable tackling more difficult repairs may, for
example, replace damaged sheathing and rafters and do their own re-roofing.
Many books and periodicals about more difficult jobs are available in libraries
Dont take on an entire re-roofing job unless youre in excellent physical
shape, unafraid of heights, well-informed about building construction,
and willing to do very hard, tedious work. A bundle of shingles weighs
about 70 pounds, and a typical roof might require more than 60 bundles,
each of which has to be lifted to the roof. Also be wary about re-roofing
on a steeply pitched roof (more than five or six inches vertical for every
12 inches horizontal), a roof that requires new structural work underneath,
or one with numerous dormers and other obstructions. Dont even consider
putting on a built-up roof, and think twice about installing a tile roof;
the tools and skills required for such roofs are beyond the reach of most
homeowners. Finally, remember that thousands of dollars worth of damage
can result if your house has no roof when it rains. Although you can provide
temporary covering to avoid or minimize damage, professional roofers can
almost certainly work faster than you can.
Youll more successfully choose and deal with roofers if youre aware of
all that can go wrong.
Where water has leaked and sheathing has rotted, shingles are simply nailed
onto the rotten sheathing. The nails will pull out and shingles will come
Unseasoned materials are used to replace sheathing. The materials will
shrink, causing shingles to buckle.
At points where two planes come together, flashing is not put into place
or woven valleys of shingles are not used. Leaks will occur at the joints.
Old flashings are reused although they are corroded, eroded, or punctured.
They will leak.
No counterflashing is used, or what is used is not properly embedded in
the mortar or adequately attached. Counterflashing should be installed
over flashing materials to keep flashings dry; without it, water will leak
past the step flashing.
Valley flashings are too narrow. In a heavy downpour, water will wash up
under the shingles and turn back down under the flashings.
Flashings are not made of heavy enough material. They will crack, puncture,
or erode away, causing leaks.
Instead of a series of short- to medium-length pieces stepped over one
another, flashings consist of long pieces, nailed at various places along
their length. With expansion and contraction caused by temperature change,
the metal will fatigue and split or nails will pull out.
Nails are too short. If nails are not long enough, they may pull loose.
Nails do not have barbed (or otherwise deformed) shanks. They may pull
Nail heads are too small. They may puncture the surface of the shingles,
hastening deterioration and leaks.
Nails are driven into knotholes or spaces between sheathing boards. They
will work their way up, forming lumps in shingles.
Too few nails are used. Shingles may come loose in wind or with repeated
Successive courses of shingles are not overlapped, as required for the
slope of the roof. Water will back up under shingles or go through nail
Cutouts or edges of shingles on successive courses are not adequately spaced,
or openings of one course are too near nail holes on the course below.
Water may weave from an opening on one course down through a nearby opening
or nail hole in the course below, causing leaks.
Too little space is allowed at joints of wood shakes or shingles. They
may swell and buckle in damp weather.
Shingles or slates are too heavy for the framing. Sagging of the roof may
damage shingles or create leaks where shingles do not lie properly.
Damaged or cracked shingles are used. They may leak.
In a new roof that is applied on top of an old one, tops of shingles are
improperly placed against butt ends of shingles on the roof. The roofs
surface will appear uneven.
The courses slant or the cutouts and edges are improperly aligned (neither
random nor regular). Appearance suffers.
Bulges and warps in shingles of a previous roof are not flattened. Appearance
suffers and leaks may occur.
Gutters sag, are loose, do not slope adequately, or are installed too low.
If gutters overflow, or if water flowing from the roof overshoots gutters,
it may cause water to enter the house.
A built-up roof is applied over a metal roof. The metal will expand and
contract, tearing the felt.
Bituminous paint is used on a metal roof. It may form bubbles, allowing
the metal to rust underneath.
Better Business Bureaus
Santa Clara and Santa Cruz Counties
1112 S. Bascom Avenue
San Jose, CA 95128
All Other Bay Area Counties
1000 Broadway, #625
Oakland, CA 94607