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BullDogg 10-11-2007 05:14 AM

Shingle Over Or Remove/replace?
My first time on a forum like this.

I am just starting to research a DIY job on my primary home. The roof has not been replaced since the home was built in 1989. Although no leaks it is looking faded and the asphault is pebbling off.

The home is one story hip and gable roof over 3990 sqft of house (big order for DIY, I know). Its been many years since I assisted in singling a roof, however it was not difficult then using just shingle, hammer and nails. I do have three teen age boys who will be "eager" to help...well, they'll help anyway. The home is in the Tampa Bay, Florida area.

For the more experienced the question is whether I should shingle over the existing roof, or remove and replace? What are some common first overlooks for estimating the job in both expense and materials? Any other "by the ways" to help?



adawg 10-11-2007 06:02 AM

I've been told that 2nd layers build excess heat and do not allow a proper cooling cycle. THis means the new shingles will age prematurely and need to be replaced much sooner than if you did a complete tear off and re-roof. But, I am not a roofer...

jogr 10-11-2007 02:26 PM

You have three teenage boys for tearoff so that's easy!

I hate tearing off shingles but I hate shingle overs more. I'm sure they can be done ok but I always felt like the roof wouldn't look as nice, hold up as long - and why carry all that extra weight on your roof (I guess you don't have to worry about snow load there).

Measure the roof carefully, don't forget to account for shingles for the ridge. Plan on finding some roof sheathing that needs replacement. Use architectural (dimensional) shingles instead of 3 tab. They look better, go on easier and seem to hold up better.

That's a mighty big roof. Tear off and reroof a section at a time. Start small until you get a feel for how much you can do at a time. I imagine it rains pretty frequently there and you don't want tearoff to get ahead of what you can shingle before the next rain. Make sure you tarp the transitions between new and old really well as you work your way around the house.

Make sure you use those boys! They will never forget helping Dad with the roof.

Mart 10-11-2007 02:29 PM

Be careful about shingling over. I don't know if that will affect the warrenty of your shingles or not. Check it out!

Ed the Roofer 10-11-2007 06:09 PM

The age of your roof and the probable inherent brittlness will likely cause secured nail fastening detachment.

The more brittle the underlying roof system is, the more chances you have for the nails to move laterally, sort of like a toggle affect. This will eventually lead to nail displacement and loose shingles.

Additionally, the trapped air between the old roofing shingles and the new roofing system will allow contained areas of heat pockets, or heat sumps as I have elsewhere heard it described. This additional trapped heat will significantly cause the new roof system to fail prematurely.

As a rule of thumb, I believe that you should factor in a minimum of a 25 % decrease in shingle life longetivity for each additional layer of roofing shingles applied.

Further, due to this premature failure and the necessity to do the roof over again in less than 15 years, you will not have the personal desire and the availability of the sons to assist you in your tear-off endeavors.

Also, the additional packing along the eave and gabled edges is unsightly and will reduce the ROI of you home if you decide to place it on the market.

Finally, your roof square footage will be a major undertaking and you should allow for over a months worth of weekends to miss out on other essential family activities.

Who amongst your family members has any day to day knowledge of the proper and correct application methods and will adhere to them accordingly?

What will you do if the weather takes a turn for the worse, while stripping off the old roofing materials?

How much carpentry expertice do any of you have in the event that some of the deck sheathing needs replacement?

This is a very large project for a DIY with your kids.


Big Bob 10-11-2007 07:46 PM

Roof over is bad practice anywhere in FL. I am not aware of any manufacturers warranty on a roof over. Ed has detailed many of the reasons above. Besides that they look like dodo. FL humidity is just too tough on roofing materials to allow roof overs except as a foolish option of last resort.:no:

skymaster 10-11-2007 09:24 PM

4o squares, a tearoff, sheathing repair,replacement, caps , debris removal,

DIY? Not this one. REALLY call a roofing contractor, get a beer, sit in the pool and watch em work. Roofing is NOT an enjoyable sport.
No insult intended, just loading the shingles is an absolutely miserable bear of a job. 3 tabs are about 125 lbs per square or more. 40 sq, probably 5000 lbs or more, plus paper, nails etc in FLA heat nah ya dont wanna go there

Docfletcher 10-11-2007 09:35 PM

Don't put your children or yourself at risk. Besides any mistakes the kids make you most likely won't catch. :yes:

BullDogg 10-11-2007 11:00 PM

To all -

This is what is so great about forums like this. All suggestions and comments have given me pause to reconsider my initial plan. I had not considered issues of warranty or heat build-up with an shingle-over. I'll get some more job estimates form area roofers. Thanks for your help.

All the best - BullDogg

the roofing god 10-11-2007 11:07 PM

3-tabs(25 yr)start at 235 lb.s per square,you need to strip it check the decking,tape all the plywood seams,install eave protection,felt,flashings,ventilation etc,and dependent on location a metal roof may be a far better choice for you

Ed the Roofer 10-12-2007 02:51 AM


I had to tape the vertical seams of the OSB overlay on a skip sheathing job once. The OSB was specified by the GC, so that was not my choice.

We did the roof in December or January and it looked perfectly flat. Th elderly lady HO refused to add additional ventilation.

3 months later, when the spring warmth arrived, the 4 foot vertical seams in many locations were telegraphing through the shingles.

Upon going there to check it out and removing the 3=tabs from the multiple 4 foot areas, we found that the felt paper had ballooned up on these joints. Certainteed advised us after checking it out, that the lack of additional exhaust ventilation was the culprit.

Is this the reason you tape the seams?

If not, what other reasons do you list for that necessity?



the roofing god 10-12-2007 09:15 AM

actually,I don`t do it,but it is code now in florida,which is where the poster said he lives,also shingles take a beating there from the salt air,that`s why I said he should consider metal

Ed the Roofer 10-12-2007 12:05 PM

On the one I had the problems with, after we removed the shingles and cut the bumps out of the felt paper, we installed duct tape on the vertical seams and then slap stapled it down also. Then we re-applied new felt and the shingles.

It is now about 6 years later and they are still doing fine.


the roofing god 10-12-2007 09:39 PM

this is in regards to the seam tape required in florida on plywood seams:
Mitigation Manual" referenced therein
For the purposes of this guideline the code sections specified will be from the Hurricane Mitigation Retrofit Manual.
I. Supplemental Fasteners and Secondary Water Barrier

A. Trigger:
When a roof on an existing site-built, single family residential structure is replaced. [According to the 2004 Florida Building Code (Section 1502 Definitions): ROOF REPLACEMENT: The process of removing the existing roof covering, repairing any damaged substrate and installing a new roof covering.]

B. Requirements:
1. Roof deck attachment and fasteners shall be strengthened and corrected as required by section 201.1.

2. A secondary water barrier shall be provided as required by section 201.2. Self-adhering polymer modified bitumen tape or sheets (peel and stick products) must comply with ASTM D1970
C. Guidelines
Q. Is there a required inspection (or affidavit certification) for the supplemental fasteners?
A. Yes
Q. Who can perform this inspection (or affidavit certification)?
A. Florida Professional Engineer, Registered Architect, Licensed General Contractor, Building Contractor, Residential Contractor, Roofing Contractor or persons certified in the structural discipline under FS 468.
Q. Can existing sheathing fasteners be used to satisfy the supplemental requirement in Table 201.1 where wind speed is greater than 110 mph?
A. Only if the existing fasteners are 8d clipped head, round head, or ring shank and spaced at 6" or less on center.
Q. What type of fasteners must be installed to satisfy the supplemental requirement in Table 201.1?
A. Supplemental fasteners shall be 8d ring shank nails with round heads and the minimum dimensions as specified in 201.1.
Q. Are the enhanced fastener requirements and secondary water barrier required on new construction?
A. No.
Q. Is there a required inspection (or affidavit certification) for the secondary water barrier?
A. Yes
Q. Who can perform this inspection (or affidavit certification)?
A. Florida Professional Engineer, Registered Architect, Licensed General Contractor, Building Contractor, Residential Contractor, Roofing Contractor or persons certified in the structural discipline under FS 468.
Q. Can self-adhering polymer modified bitumen (peel & stick) be applied directly to the roof sheathing in the HVHZ as well?
A. Yes for the purposes of complying with these secondary waterproofing requirements only. (Subject to local approval)
Q. What is the minimum thickness of self-adhering polymer modified bitumen that can be installed?
A. A minimum of 40 mil is required, Per ASTM D 1970.
forget about DIY IN Florida:wink:

skymaster 10-12-2007 10:17 PM

RoofingGod: under guidelines: Q are the supplemental fastners and secondary water required on NEW CONSTRUCTION?
Answer is NO???????????? WTF????????????? SAY WHAT?????????
No wonder FLA has the rep it has earned.:no: :eek:

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