Urgent, Secondary Water Barrier Miami Dade Unincorporated

Hi, I’m in the middle of a roof replacement in unincorporated Miami Dade county for a site built single family home and my contractor stated that no secondary water barrier is required by code, that such barrier is always optional. However, the county requires the contractor to sign the affodavit stating that a secondary water barrier has been installed (he didn’t have this at first inspection and inspector conditionally approved). My understanding is that if we only have UL 30 under the shingles, then after 2008, taping the joints between all plywoods is required. I’m afraid of asking the county because if I am unfortunately right, they may need to start over? Contractor said in his 20+ years doing this, he has never heard this is required nor had any issues? Is he right??

Whoever has the power to make your life miserable over the longer term is the one to consult. Have you heard this one? “Ignorance of the law is no excuse.” Despite the contractor saying he has never encountered this, you might also consider the possibility he has never chosen to comply with this? You need to cover your own behind and by burying your head in the sand, an avoided conflict will possibly reward you with an enduring problem. You know what to do and listening to anyone who has no skin in the game declare otherwise is foolish. Take a deep breath and do the right thing.


Mom and dad. (Well that’s what they’d say anyways)

Dont ask the county anything.
He is having it inspected.
He knows the law.
He knows he cant pass it if he goes against it.
Let him pass his inspection
Or fail it and correct it on his own.
He is the one that is facing the inspector every day.

As of new code changes that happened in Jan
The florida law now is either
1.30pound d.226 or synthetic with tape on all the plywood seams.
2. 2 ply 30 pound d.226
3. 2 ply synthetic
4 Self-adhered ice and water shield.

So what we are doing is either number 3 or 4
Depending on the pitch.
4/12 pitch and below i am installing self-adhered.
Everything steeper than that gets 2 ply synthetic.

There is a possibility your county is more strict and requires more.
I am not in that county.
But i do know that it is the most strict roofing code in the world.

Or maybe mine is… lol

Who comes up with these codes?

Insurance companies!

Thanks everyone! The wrinkle here is that inspectors seem to rely on the signed and notarized affidavit that says that they have complied with the code and installed the secondary water barrier. I suppose the idea is that since the deck is already covered with UL 30 at the time of first inspection, the county relies on that certification. Here’s a link to the Miami Dade requirements on this:


“I _ certify that the roof decking attachment and fasteners have been strengthened and corrected and a secondary water barrier has been provided as required by the “Manual of Hurricane Mitigation Retrofits for Existing Site-Built Single Family Structures” adopted by the Florida Building Commission by Rule 9B-3.047 F.A.C.”

So are contractors simply signing this and not stopping to think what is it that they are signing? Am I getting less than what the code requires? Maybe it’s also a stupid requirement and it ultimately doesn’t matter?

The contractor’s answer that such barrier “is always optional” makes me think he does not understand this. If he were to say, OK, for yout type of roof or whatever this does not specifically apply to you, then fine. But saying that it’s always optional does not make any sense based on the requirements I noted above. Clearly it is a requirement for certain types of roofs and it gives you to very specific options on how to comply. Roof is 90% + done.

When you do the 2 ply synthetic,do both layers have to have the crazy nailing?

6 inches on center on the edge of the laps.
One run of 12 inches on center in the middle of the 24 inch lap.( approx, depends on height of the roll)


Well that’s a roof, it’s a shame you have to punch a bunch of holes in it when the shingles are installed.


Miami-Dade accepts 30lb felt as a secondary water barrier. They are not going to force people to spend all that money. Wind Mitigation laws are badly written, imo.
If you are after premium discounts, however, the insurance companies do not recognize 30lb felt as a secondary water barrier.

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The double protection seems overboard to me, but I don’t have to deal with it. My work area starts at 65 miles from the gulf of mexico. I’ve noticed many new homes getting the ZIP system for roof decking and walls. The ZIP roof system doesn’t require underlayment, as it is incorporated into the decking. You have to tape the joints for the system. Could it be that Florida contractors were using the ZIP system and not installing underlayment, so the minds that have nothing else to do said, HEY! lets make them put 2 layers of protection?

Lets face it, if it aint a watershield, your going to put 10k nail holes in the underlayment. The only time it might be of use, is if the shingles blow off and it stops raining. With the Miami-Dade codes, if the shingles blow off, I’m pretty sure the underlayment, roof accessories and decking are coming with it. Just my simple opinion.

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The zip system doesnt work.
Everyone is figuring it out.
Its fine for walls,
But not for the roof.
Does it make a fine decking? Yes!
But it still need underlayment.
Is it a very rot resistant decking?
But it still needs underlayment.

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Thanks everyone! I will discuss in more detail with the contractor, but it sounds from the above that the county is not actually requiring then more than UL 30 as secondary.

I am nuts and in miami-dade co with a roof I would like to stay on

yes they do a single layer of nailed paper no tape under it no tar then nail on shingles

we watch those blow off in andrew’s 150 mph winds

now the hurricanes blow 200mph thanks to warming ect

I needed a new roof and my post andrew roof was 25+

so I over did it to the max
3 layers of 5/6’s ply staggered screwed and glued end joins tarred then plastic/paper and peal&stick
then doubled metal 5v long screws in to the beams and 1/2’’ SS cables over the roof to the slab
just to be sure the roof ain’t going flying in a cat 5

no shingles they are fine in non hurricane areas
but you ain’t in one
metal is the answer get a loan if needed but you need a roof that will not blow off

The code in the high wind area of Miami requires a lot more than 30 pound felt. We installed a complete peal and stick roof under all of the tile jobs we did and peal and stick base under comp roofs with round cap nails. About 1 round caps per sq ft. You can use several different base sheets however I would double Check about the #30 base.