Cost of overlaying 3-tab asphalt shingles with dimensional (overlay, how much, roofing)

[bjornb17]

Hi everyone... New member here but have been browsing for over a year.

I bought a new house in January, and it came with the 3-tab flat asphalt (20-year?) shingles. Dimensional shingles were not available as an upgrade but I really love the look of them. Would it be possible to overlay the existing shignles with dimensional shingles? How much would something like this cost? The house is a 2000 square foot one story home with a simple roof geometry.

Thanks!

[Cosmic]

Think what you are calling dimensional we normally call architectural shingles.

Those can be put in a two layer job over 3 tab provided the old shingles are in decent shape.

Who knows what it might cost for your house. Get a price for a bundle of the shingles you like. Estimate the square feet in your roof. Divide that by 100, mutliple that by 3, multiple that by the price of your shingle. Multiple that number by .2, add that to the cost of the shingles. That is about the material costs for your job.

A decent full job with labor is 2 to 3 times the material price, depending on your area / contractor.

[bjornb17]

Yep, the "old" shingles are in fact brand new but looks incredibly bland. Thanks for the help! I would give you reps except i do not know how.

[MikeJaquish]

You will need to add a minimum of 10% waste additional for overlaying three tabs with architectural.
Architectural shingles are designed to expose 5 5/8" to the weather.
Three tabs expose 5" to the weather.
For every course of shingles, you are giving up 5/8" of the architectural shingles' expected coverage.
And it makes a lousy looking job, since the architecturals' design is based on the proper exposure.

[bjornb17]

Originally Posted by MikeJaquish

You will need to add a minimum of 10% waste additional for overlaying three tabs with architectural.
Architectural shingles are designed to expose 5 5/8" to the weather.
Three tabs expose 5" to the weather.
For every course of shingles, you are giving up 5/8" of the architectural shingles' expected coverage.
And it makes a lousy looking job, since the architecturals' design is based on the proper exposure.

I am not quite sure I understand. Why would it be different than just putting the architectural shingles over the bare roofing? I am new to this all so I don't know the ins and outs.

[poconoproud]

you're best bet is to call in at least 3 roofing contractors in your area for a quote...what's the going rate where I am may not be prevailing where you are.

[Cosmic]

The exposure is not a problem.

There is a way to use a fill section of the 3 tab to basically cancel out how the overlay works. Sort of difficult to explain but easy to do. You tack in an extra fill section on the first old layer exposure on the first course that gets rid of the bump between courses. This makes it sort of like a new smooth layer without having to worry about the butting problem. Can be done every place it occurs. Each new shingle is level with itself over its entire plane. You need some extra 3 tabs to cut and do it. Most roofers know how. As the creep occurs, you repeat as necessary. Really can't tell where it has been done. In effect some areas have 3 layers for a very small section.

You can also just do another layer of 15# felt over the old layer, then do the new shingles. Works to bridge the old butting problem. Maybe not the best way but it can work.

Preferred is to strip all old layers if doing architectuals. I might go that way in most cases but it can be done with the right techniques over good conditioned 3 - tabs like you have. You get two good conditioned layers, waste not, want not, for cheaper money. Might have to have the right roofer. Most prefer to strip to bare metal for each new layer of architecturals.

[MikeJaquish]

All assuming that you have standard 3 tabs, and not metric shingles:

Look at the exposure in the standard shingle in Section 2 on Page 3:
http://roofing.owenscorning.com/docs...b_Install2.pdf
It is 5".

Look at the exposure in the shingle drawings in Section 4:
http://roofing.owenscorning.com/docs...ge_install.pdf
5 5/8" exposure.
So, unless you work to shim up shingles as needed, as Cosmic said, you will only get the 5" exposure your three tabs have already.
I.e., there is more than one way to jack leg in a roof and make it look crappy.

Personally, I would find a way to get less bored with the roof that is in place. Maybe take up fishing or something...
You will likely not find the skills available to make a good architectural shingle job over the three tabs.
If the shingles are still good, let them wear out more, and strip them and get it done right.
That will let you save a few more bucks and go with a REALLY interesting shingle.

[Cosmic]

Originally Posted by MikeJaquish

So, unless you work to shim up shingles as needed, as Cosmic said, you will only get the 5" exposure your three tabs have already.

I'm trying to remember exactly how it was done. First you filled the first course exposure with new pieces of 3 -tab. Then you skipped up ways and removed some, least I think. Anywho, at some point you could put in 90# roll roofing to give a huge clear flat area to start the architecturals. IIRC that worked out to compensate for the creep for something like 28 feet of courses or it was some big number like that. Enough to do most garages or smaller houses. It actually was pretty fast and all the extra layers, weight was down by the edge boards.

If I got up on a roof again, think I could figure it out, somewhere I have it in a notebook. There was some nailing trick too and how the tab side of the 90# went on. Maybe it was two spliced 3 tab pieces one on either side of the 90#. I'm foggy, been a long time but it can be done.