Reuben's Home Inspection Blog

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Improper Shingle Nailing = Defective Roof Installation

One of the most common defects I find with asphalt shingles is improper nailing.  The manufacturers of asphalt shingles give specific instructions on how to fasten shingles, and they're all pretty much the same.  Unfortunately, following those instructions seems to be a difficult thing to do for a lot of roofers in Minnesota.  The two most common nailing defects that I find with shingles are overdriven nails and improperly located nails.

Overdriven Nails

Most roofers use pneumatic nail guns to nail down shingles.  When the pressure is set too high, the nails get driven in to the shingles too far, plain and simple.  When the nails are overdriven, the heads of the nails punch right through the mat of the shingle.  This voids the shingle manufacturers warranty and greatly increases the potential for shingles to come loose and blow off, possibly in sheets.

The diagram below shows what proper and improperly driven nails look like.

Shingle Nailing Diagram

The photos below show several examples of overdriven nails.

Overdriven Nails 1

Overdriven Nails 2

Overdriven Nails 3

Overdriven Nails 4

Overdriven Nails 5

Improperly Located Nails

The other most common nailing defect that I find with asphalt shingles is improperly located nails; specifically, high nails.  When shingles are located too low on a shingle, it's an obvious defect that anyone with a good eye can usually spot from the ground.  This is probably why I don't find this defect all that often; it's just too obvious of a defect for most roofers to leave uncovered.

Low Nail

The more common and problematic nailing problem is to have nails located too high on the shingle.  There is a fairly narrow strip on every shingle where it's acceptable to place the nail.  When properly placed, the nail will actually catch the top edge of the shingle below it.  When nails are located too high on the shingle, they never catch the shingle below, which effectively cuts the amount of nails going in to each shingle in half.  Hopefully my diagram below will help to illustrate this; the blue dots are supposed to be nail heads.

High Nail Diagram

The photos below show examples of high nailing.  Yes, I know what I did there.

High Nail 1

High Nail 2

When shingles are improperly fastened, they have a tendency to slide and rip out of the nails holes, and this won't be covered by the manufacturers warranty.  When the entire roof covering is installed like this, there is no simple fix.  Either the new buyers need to accept the fact that their roof will be prone to having shingles blow off, or the roof covering will need to be repaired or replaced.

Shingles Delivered on top of brand new roof

These installation defects can't be seen from the ground, even with a very expensive pair of binoculars.  For this reason, you shouldn't expect most municipal inspectors to identify these issues; it's outside the scope of their inspection.  I wrote about this topic here - Who Inspected Your Roof?  If you want a thorough roof inspection, you would do well to hire a home inspector who can will access the roof.

Reuben Saltzman, Structure Tech Home Inspections

        

Comment balloon 34 commentsReuben Saltzman • May 01 2012 03:11AM

Comments

Hi Reuben, excellent post.  Great illustration of proper & improper installation.  You will make roof experts out of us! lol

Posted by Bob Miller, The Ocala Dream Team (Keller Williams Cornerstone Realty) over 6 years ago

Reuben, this is great advice...for some reason many of the home inspectors all of a sudden are not physically going on the roof during an inspection which surprised me.  On one home if the inspector had, the buyers would have found out that the shingles were in much poorer condition than he thought.  Like you said binoculars do not take the place of physical presence...I think it is a very important question for buyers to ask before they hire their home inspector- do you venture onto the roof?!

Posted by Ginny Gorman, Homes for Sale in North Kingstown RI and beyond (RI Real Estate Services ~ 401-529-7849~ RI Waterfront Real Estate) over 6 years ago

Ginny beat me to the punch. You said;

"If you want a thorough roof inspection, you would do well to hire a home inspector who can access the roof."

I think you should say; who will access the roof. I had a roof recently that was pre-inspected. The inspector stated the roof had 8 years of life. He must have looked at it from the street. The roof was shot. 

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) over 6 years ago

Bob - thanks!

Ginny - there is definitely no substitute for getting on the roof.  Many inspectors talk about roofs that are too steep to be walked, too high to access with ladders, too dirty, etc... and I find that all of those conditions might add up to about 5% of the homes that I inspect.  The rest of the roofs can be walked.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Good point, James.  I'm going to change my wording :)

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Done and done.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Hey Rueben,

There has only been one roof that I did'nt get up onto.

This was a tile roof and it was raining. Yes I said raining. It was a couple of years ago.

As far as the shingled roofs being nailed properly. Even the best roofing companies don't do it right.

Have a great week ahead up North.

Best, Clint McKie

Posted by Clint Mckie, Desert Sun Home, Comm. Inspection 1-575-706-5586 (Desert Sun Home, commercial Inspections) over 6 years ago

Great blog Reubs!  As to improper nailing, I find the most common thing to be nails driven at angles.  These gun guys seem to really get off on how quickly they can zap in a shingle, with 8, 12 nails driven very quickly.  Of course, doing it that way the gun cannot be properly placed.  And, um, gee, they miss the proper line!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 6 years ago

I have seen this problem in many homes. What if they would slow down and do the job right?

Posted by Harry F. D'Elia, Investor , Mentor, GRI, Radio, CIPS, REOs, ABR (Real Estate and Beyond, LLC) over 6 years ago

Clint - I'll bet you schlepped your ladder around the house and still looked at the roof from several angles though, right?  

Jay - I definitely see my share of angles nails as well.  It might not be quite as bad as nails completely punched through the shingle, but it's certainly an installation defect that won't be covered under warranty.

Harry - they would get less work done and make less money?

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Great post Reuben. This is something I never would have thought of. Most people think overdriving a nail isn't so bad!

Posted by Donald Reich (Prudential Centennial) over 6 years ago

Another topic that I haven't thought much about--thanks again for the lessons!

Posted by Peggy Chirico, REALTOR® 860-748-8900, Hartford & Tolland County Real Estate (Prudential CT Realty) over 6 years ago

Reuben -- This is a very informative post and it is well illustrated by your photos.  Nicely done.

Posted by Joan Whitebook, Consumer Focused Real Estate Services (BHG The Masiello Group) over 6 years ago

Reuben, getting up on the roof is the only way to know for sure. Assuming a roofing company knows what they are doing may not be a good thing.

Posted by Michael Setunsky, Your Commercial Real Estate Link to Northern VA over 6 years ago

This is a great post....and makes me think about the few times when my buyers have used an inspector who does not walk the roof.

Posted by Kathryn Maguire, Serving Chesapeake, Norfolk, VA Beach (GreatNorfolkHomes.com (757) 560-0881) over 6 years ago

I  have seen this...Some of those nails that are put in improperly cause problems (leaks) down the line

Posted by Richie Alan Naggar, agent & author (people first...then business Ran Right Realty ) over 6 years ago

Well done, Reuben.  If an Inspector does not walk the roof, he is not really inspecting it, just going through the motions.  Of course, there are exceptions in the case of some roofs where specialized equipment may be needed to safely access it.

Posted by Steve Stenros, CREIA MCI, ICC, ACI Home Inspector,San Diego (Poway,La Jolla,Del Mar,Mira Mesa,Carlsbad,Escondido,Temecula) over 6 years ago

Looks familiar to me an obviously the other inspectors. These are common installation problems but the roofers that come out and evaluate after the report often brush it off, possibly because they all do it.

Posted by Rob Ernst, Reno, NV-775-410-4286 Inspector & Energy Auditor (Certified Structure Inspector) over 6 years ago

Reuben, very well done post.  I think it can be more difficult to "properly" nail shingles with a nail gun than it is worth.  Gun settings, user error, and just plain being in too much of a hurry can make for a very expensive roof if the whole thing has to be done a second time.  I do a random check of the nailing---but only on shingles that are easily lifted up.  If the tabs are really stuck down some of these defects are going to be under-reported unfortunately.

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 6 years ago

Reuben  -- as others have mentioned, this goes back to the "get it done quick" school of roofing, rather than "get it done right" group of roofers.   The latter also seem to remember to remove the plastic strip from the tar.

Posted by Steven Cook (No Longer Processing Mortgages.) over 6 years ago

Reuben:

Such a great article about nail placement on roofs.  I am going to make a copy and keep it so I can show my clients the right and wrong way to apply a roof.

Posted by Evelyn Kennedy, Alameda, Real Estate, Alameda, CA (Alain Pinel Realtors) over 6 years ago

Reuben,

They must use the same roofers in Minny as they do here ; ) Another thing I see with the pneumatic is if the compressor is not large enough (or a good one) to run the guns correctly so they crank them up to get more shots before recharge and then you see over driven nails in the beginning then proud nails at the end of the cycle.

I see a lot of shingle blown off in the spring and fall from poor nailing practices. 

Posted by Donald Hester, NCW Home Inspections, LLC (NCW Home Inspections, LLC) over 6 years ago

I'll go with what you say. I've seen enough shingles blown off here in Michigan.

Posted by Robert L. Brown, Grand Rapids Real Estate Bellabay Realty, West Mic (www.mrbrownsellsgr.com) over 6 years ago

Donald R - usually overdriving a nail by 1/8" is no big deal :)

Peggy - thanks for reading!

Joan - thanks.

Michael - you got it.  There's just way too much stuff that can be missing from the ground.

Kathryn - you gotta wonder what they're not seeing. 

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Another do-it-yourselfer job using way to much prssure with the nail gun.

Posted by William Feela, Realtor, Whispering Pines Realty 651-674-5999 No. (WHISPERING PINES REALTY) over 6 years ago

Richie - especially underdriven and low nails.

Steve - I have the same take.  You're right, not all roofs can be safely walked, but the ones that can't seem to be few and far between.

Rob - I know of a great home inspector who serves on some kind of roof advisory council.  I've had him go in after the fact when roofers claim this stuff doesn't matter; in those cases, the roofers usually end up having to do full tear-offs; they can't argue with him :)

Charles - thanks.  Someone left a comment on another site that I published this post at, and it made me think of you:  If I've said it once, I've said it a thousand times -- the worst thing to ever happen to the construction industry was the invention of the pneumatic nail gun!  

You're right about spot checks, of course, and I take the same approach as you.  If the tabs are stuck down, I can't check this stuff.  I don't break the seals to figure this stuff out.  I usually find these issues on the north sides of newly installed roofs.

Steven - yep, definitely an issue of just not taking the time to do it right.


Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Evelyn - much appreciated.

Donald H - yes, I'm sure it's the same crew doing the work ;).  I'm sure you're right about the reasoning for too high of pressure.

Robert - I'm sure you have.

William - most of these are professional roofing crews, believe it or not.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

Reuben - Good post.  I learned something new today.  Thanks for sharing.

Posted by Jim Patton, Realtor - Stanislaus & Merced county Realtor. (Century 21 M&M - 209-404-0816) over 6 years ago

Reuben

Just thought I would let you know I found this through a repost by Chris Smith. Amazing how something so simple if done incorrectly can be such a huge hassle. cheers cvc

Posted by Curtis Van Carter, Your Napa Valley Broker Extraordinaire (Better Homes & Gardens Wine Country Group) over 6 years ago

Reuben--Your posts are very informative. Do you work all over the Twin Cities metro...Ever go north and east?

Posted by Teri Eckholm, REALTOR Serving Mpls/St Paul North & East Metro (Boardman Realty) over 6 years ago

Jim - thanks!

Curtis - it's really easy to mess up a roof, isn't it?

Teri - thanks.  Yes, I definitely work all over the metro area... even as far as WBL :)

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 6 years ago

The contactor who did my mom's roof was suppose to use 6 nails per Timberline shingle.  He used 5 with a gap of 16-21 inches beteen the 4 th. and 5 th. nail.  the self sealing tabs have melted down is there anyway to add additional nails to this entire roof without distroying it?

Posted by paul about 6 years ago
I purchased a brand new custom home 2.5 years ago by a company that builds a couple at a time. We experienced 50 mph winds one day and about a 1/4 of the roof, in various spots, came off. Insurance and an engineer came in and stated that the roof was improperly installed. Well, yeah, we were the only house impacted by the winds. The house came with a 1 year warrantee. Will cost me about 15K to replace. Repairs are I don't feel will resolve the issue and I will be paying another deductible next windy day. Thoughts? Do I have any leg to stand on? The tiles are good quality - better than most in the area so I cant go there. It is the installer - again one year warrantee.
Posted by Touchdown Tom over 4 years ago

@Touchdown Tom - those are good questions for an attorney.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 4 years ago

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