What drives the cost of a roof in Los Angeles County

Squares, not square feet

Roofers price in squares. One square is 100 square feet of roof surface, and the roof surface is always bigger than the floor of the house because the roof is sloped. A single story house with 1,800 square feet of floor can easily be 22 or 24 squares once the pitch is counted.

This is the first number to get straight, because every other number hangs off it. Ask any bidder how many squares they measured and make sure all of them say roughly the same thing. When one quote says 19 and another says 26, one of them has not been on the roof.

Pitch, and whether a crew can stand on it

The steeper the roof the slower the work and the more equipment it needs. Past a certain slope a crew cannot walk it, so the job needs staging, harnesses and roof jacks, and a day becomes two.

Pitch also decides what may go on the roof at all. Below about three in twelve, shingles stop working and the roof needs a sealed membrane instead, which is a different trade and a different price.

Tear off against going over the top

Removing the old roof costs labor and it costs disposal. Laying new shingles straight over the old ones skips both and it is always cheaper on the day.

It is also how a quote gets to be the low one. Nobody sees the decking, so soft spots and old leaks stay in the building, the weight sits on rafters sized for one layer, and most manufacturers will not warranty the result. When one quote is far under the others, check whether it includes a tear off before you decide anybody is being generous.

Decking, which nobody can price until the roof is open

Under the shingles is the wood deck, and until the old roof comes off nobody knows what it looks like. Rot around a chimney or along an eave is common and it has to be replaced before anything goes back on.

An honest quote says what a sheet of replacement decking costs and how it will be counted. A quote that says nothing about it is not cheaper, it is unfinished, and the conversation is going to happen on the day with the roof open and no leverage.

Material, and the parts of the system you never see

The shingle or panel is the part people compare, and it is not where quotes usually differ. The difference is underneath. Underlayment, the ice or water barrier at the eaves in cold climates, the valley detail, the flashing at every wall and chimney, the boots on the vents, the drip edge.

Those are the parts that decide whether the roof leaks, and they are the easiest to leave out of a number. Ask for them by name.

How hard the roof is to get at

A simple gable on a single story with a driveway beside it is the cheapest roof there is. Every complication adds hours. Two stories, valleys, dormers, skylights, a steep drive, no room for a dumpster, power lines over the approach, a fence that stops a truck getting close.

None of this shows up as a line on a quote and all of it is in the price. It is also why a quote given without somebody visiting is a guess.

Ventilation and the work that comes with a tear off

A roof is a system with the attic under it. If the attic is badly ventilated the new roof will cook from below and age early, so a good quote may include opening soffit intake or adding ridge exhaust.

That reads as an upsell and usually is not. It is far cheaper while the roof is off than as its own job later, and it is the single most common reason two otherwise identical quotes differ.

The permit and the inspection

Most places require a permit to replace a roof, and the permit brings an inspection. Both cost money and both take time.

A contractor who offers to skip the permit is offering to save you the permit fee and hand you an unpermitted roof, which becomes your problem when the house is sold or a claim is made.

When you are buying

Roofing is seasonal work and the price follows demand. Right after a storm, every crew in the area is booked and nobody is bidding softly. Late in the season, in the cold, shingles will not seal on their own and the work needs extra care.

If the roof is not actively leaking, the quiet part of the year is the cheaper part of the year.

What a quote has to say before it can be compared

• The roof area in squares, and the pitch.
• Tear off or layover, and how many layers are coming off.
• The product by name and line, not just the brand.
• The underlayment, the flashing and the eave detail.
• The price of replacement decking and how it will be counted.
• Who pulls the permit and who takes the debris away.
• The labor warranty in months, separate from the manufacturer warranty.

Why there is no price on this page

Most directories print a cost range for every city. Almost none of them can say where the number came from, and a range wide enough to be safe is too wide to be useful.

We would rather give you the things that move the number, so you can read the quote in your hand and tell whether it is complete. When a real local figure exists and can be stood behind, it will appear here with the date on it.