How much plywood for a roof?

[chocolatelab]

Ok Sorry

This is 2 questions in one day.

Rental property in Florida.

Zillow says house is 1550 square feet

Roof is super old and leaking.

2 layers of shingle and multiple repairs in the last 20-30 years.

Authorized roofing company to install new roof.

They had too replace 58 sheets of plywood.

My math says thats 1856 sq ft of plywood.

Roofer says I have about 2600 sq ft of roof and they replaced around 1800 sq ft.

Is it possible to have that much extra sq ft of roof vs sq ft of house?

[rusnak]

Yes. The roof is pitched.

[jorian]

What's the pitch of the roof?

[ben parrish]

Pitch, overhang, carport.

[Scuba Steve]

That, and you lose a decent amount of square footage due to interior walls and whatnot. It sounds plausible.

[ckelly78z]

If it were a flat roof (not likely) with the over hangs, and covering all the interior walls (these are not included in interior square footage measurements), the roof sq footage would still be alot more the the interior sq footage. Throw a decent pitch on the roof, and that number climbs dramatically.

[Porsche-O-Phile]

Trust but verify...

Should have had an owner's rep available to handle the contract - it's very easy and a temptation for un-monitored residential contractors to pad their materials charges. Generally speaking it's better to get a lump-sum price up front (that can be evaluated for quantities as part of a simple descope) or have the work done on T&M but with oversight (i.e. field verification of what's actually coming onto the site and being used - do NOT rely on just invoices for "x" quantity of material (contractors have been known to over-buy by 10%-25% on several jobs (particularly for staple stuff that's used everywhere like plywood, nails, lumber, concrete, adhesion products etc.) then build up enough stock back at their yard to do another job without having to buy anything (or very little) for it - essentially meaning you and several other customers end up paying for your neighbor's project).

Most contractors are good but there are still an awful lot of sleazeballs out there - particularly in residential. Paying somebody who knows the industry a few bucks to oversee and monitor the job is short money against getting ripped off, and can give you someone else to go after if they don't do their job.

That said (I'll get off my soapbox now) you could talk to an independent third-party contractor or estimator and have them do a QTO (quantity takeoff) for your work and see what they come up with as a number in terms of square foot for material. Most places will price up something like this for free or they may charge a modest fee for it but it sounds like it might be worth the peace of mind.

Keep in mind that there will be some excess material required due to waste but a good contractor knows how to minimize that to keep his or her costs down. A REALLY good contractor will pass that onto his or her customers in terms of better and more competitive bids. If the contractor is using a few more percent of material then the roof actually calculates out to require it doesn't necessarily mean you're being taken for a ride - 5% to 10% is probably reasonable overage to account for waste.

Make sure they install drip edges, etc.

Good luck.

[gshase]

15-20 % waist on plywood decking.

[tcar]

Originally Posted by gshase

15-20 % waist on plywood decking.

That's maybe 'waste'?

Square footage includes interior walls, usually.

[911SauCy]

Is this really a thread?

[O'Grady]

Originally Posted by 911SauCy

Is this really a thread?

Is it a waist of your time?

[911SauCy]

Originally Posted by O'Grady

Is it a waist of your time?

No, it's simple math calculations. I think OP gets that as the thread started with "Ok Sorry"

Not trying to be a jerk but if one is concerned about square footage, measure. Concerned about job being done right, get multiple quotes/opinions. And to have properly completed the job, they should have R and R all of the plywood. Now there's 69% new roof material and 31% 20-30 year old stuff.

That's a 2/3rds arsed job.

And yes there's always waste, but not 15-20%, usually about 10%.

(My family builds houses, but don't take my word for it. There are contractors on the board)

[Crowbob]

You want enough roof so it goes all the way to the edge.

All the edges.

[chocolatelab]

Originally Posted by ben parrish

Pitch, overhang, carport.

I think this is it.

After reviewing the pictures there is a large carport plus front and rear entries that make the numbers make more sense.

I did get multiple quotes and am very happy with the contractor.

I wasn't so much second guessing him as I was second guessing my own assumptions about roof sq ft vs house sq ft.

[rusnak]

Now that's answered, I was wondering who's Zillo? Any you're renting out a house in Florida while you live in California? Wait till you have to calculate the quantity of shingles and flashing. I believe the technical quantity will be a metric ***** ton.