Definition & effects of asphalt shingle laddering or ladder pattern installation. This article series defines shingle laddering - an installation pattern, and it explains how to identify & evaluate shingles installed in this "ladder pattern".

The information here describes the various sorts of roof leak, wear, and cosmetic issues caused by shingle laddering as an example of something a bit less than the "best" roof installation workmanship. These shingle laddering defects occur on both organic-mat and fiberglass-mat asphalt roof shingles.

Our page top photo shows an asphalt roof whose shingles were installed in the ladder pattern working up the roof rather than staggering shingle courses. The darker shingles mark areas of early roof shingle granule loss - a separate issue - whose resulting change in colour makes the ladder shingle pattern quite apparent.

Laddering vs stair-stepping vs proper staggering of of roof shingle courses

[Click to enlarge any image].

The photo just above shows a sloppy "ladder pattern" installation of strip-type asphalt shingles.

While opinions (and expertise) vary among roofers, this ladder pattern shingle application may not be as durable a roof installation as one which staggered the shingle offsets more than a single six inches (or in this case only 3") left and right with each shingle course.

Our page top photograph of shingle laddering also illustrates granule loss probably traced to specific bundles of shingles that were defective.

See GRANULE LOSS from SHINGLES for more about that separate problem.

The laddered shingle nailing approach, not recommended by roofing manufacturers, permits the roofer to work right up the roof from eaves to ridge, without having to move beyond reach to left or right - an approach that is appealing if the roofer is working from roof jacks or other scaffolding that s/he does not want to keep relocating.

The second photograph, below, of fishmouthed asphalt shingles in a roof shingle ladder-nailing pattern at above-right right is courtesy of ASHI home inspector Carl Gerosa, New Rochelle, NY.

 

 

Definition of Laddering, Racking, Stair-Stepping, & Staggered Roof Shingle Courses

Definition of Laddered roof shingles - Shingle Racking

When shingles are installed on a roof using the "ladder" pattern or method, the roofer nails shingles straight up the roof, leaving the left or right shingle tab un-nailed so that when the roofer begins the next vertical assault on the roofing job he can interweave successive courses of those shingles into the ones already nailed.

Some sources refer to this as shingle racking - a synonym for shingle laddering.

[Click to enlarge any image].

The sketch of shingle laddering patterns shown above is adapted from Best Practices Guide to Residential Construction and discussed further below.

Shingle Laddering is Not Recommended

As reported in Best Practices Guide to Residential Construction (Steve Bliss, J Wiley & Sons) :

For ease of installation some roofers install shingles straight up the roof, staggering shingles 6 inches or 18 inches back and forth (Figure 2-9).

Since this lines up the shingle butt joints every other course, this is considered a less watertight roof and may leak.

Note: there is an important difference between vertical alignment of the shingle tab cutouts (a cosmetic effect described above), and the vertical alignment of shingle butt joints (the abutment of two individual shingles).

Vertically-aligned shingle butt joints that appear separated by just one shingle course are more likely to leak,especially in heavy or wind-blown rain storms.

Watch out: Installing roof shingles in a ladder pattern is not recommended by any roofing manufacturers.

Manufacturers also claim that shingle color patterns may create splotches or stripes if laid this way.

Technical Objections to Shingle Racking / Laddering

The principal objection to shingle racking or shingle laddering is that shingles are less likely to be properly-nailed. That's because when installing the next-parallel up-roof laddered group of shingles nails have been left-out of the ends of the previously-nailed ladder and are not likely to be added.

A second objection to shingle laddering or racking is that the extra peeling-back or lifting of the shingle ends to install the next ladder-group can cause excessive shingle bending, weakening or even stress-cracking the end of the shingle and shortening the life of the roof.

A third, and in our opinion cosmetic-only issue with shingle racking or laddering is that shingles from successive bundles, laddered up the roof, will often not blend correctly - you'll see rectangular patterns of shingles of different colors on the roof surfacce.

Ultimately shingle nailing defects, cracks, weaknesses, or wind damage mean roof leaks or shorter roof life.

The stair-step method assures proper shingle nailling. Failing to properly nail shingles invites wind damage and roof leaks.

While you won't find an outright prohibition of shingle laddering and racking in typical building codes & standards or HUD/FHA guidelines, the objections to shingle racking are outlined in various roofing manufacturer documents we cite throughout this article including:

• PRO FIELD GUIDE for STEEP SLOPE ROOFS, GAF [PDF] (2015), retrieved 2018/02/17, original source: http://www.buildsite.com/pdf/gaf2/GAF-Steep-Slope-Pro-Field-Guide-Installation-Instructions-1224183.pdf

Roof Shingle Manufacturer Policy on Shingle Racking / Laddering

Some roofing manufacturers state that they will accept shingle racking or shingle laddering for conventional three-tab roof shingle installations but emphasize that this is not a preferred method":

Racking… is when shingles are installed straight up the roof rather than being installed using the traditional stair step method.

Does GAF Approve Of The Racking Method? Three Tab Shingles… are acceptable, but it is not the preferred method of installation because of the possible installation problems and damage if proper precautions are not followed.

All other shingles (laminated or designer shingles)… Never.

The application method and specific offsets shown in the application instructions for each type of shingle must be followed to achieve the best appearance, good wind performance, and to avoid damage to the shingles from over-bending these heavy shingles during application. - source:

• GAF, TECHNICAL ADVISORY BULLETIN: Racking of Shingles [PDF] (2014) GAF Corporation, 1 Campus Drive Parsippany, NJ 07054 USA, Website: www.gaf.com retrieved 2018/02/17, original source: https://www.gaf.com/Warranties_ Technical_Documents/Steep_Slope_Technical_Advisory_ Bulletins/English_Bulletins/Racking_ Shingles_Steep_Slope_Technical_Point_TAB_R_2011_123.pdf

(Forgetting to go back and add the missing nails is a common laddered-roof defect as Skees elaborates below. )

Examples of Damage at a Racked / Laddered Roof Shingle Installation

On laddered asphalt shingle roofs, particularly older ones, you may notice that the pattern of fishmouth occurrence on an asphalt shingle roof follows a fairly regular or stair-stepped pattern, or it may follow a regular "ladder" like pattern up the roof such as is shown in these photographs.

Or as illustrated in the photo just above and in our page top photograph as well, shingles installed using the laddering pattern may become apparent as the roof ages or wears.

That's because the fishmouthing is occurring at the butt joints of the shingles where more moisture is passing out of the roof structure into the back side of the shingle above each butt joint.

More examples of the effects of racking shingles are

at LADDERED SHINGLE FAILURES & WEAR

Definition of stair-stepped roof shingle pattern:

The phrase stair-stepped shingles is usually synonymous with ladder roof shingle patterns

Definition of staggered roof shingle course nailing patterns: 4", 5" or 6" shingle course stagger nailing

Shingles are nailed to the roof deck such that each successive shingle course is offset 4", 5", 6" or in some instructions 7" thus distributing the butt joints over a wider horizontal area.

Offsetting successive shingle courses is a recommended roofing practice by virtually all shingle manufacturers.

The sketch above illustrates a six-inch stagger or offset shingle nailing pattern. You can identify, even from the ground, the staggering pattern by noting that the shingle tab cutouts align every other course.

This is a 6-inch stagger pattern.

A four-inch shingle offset pattern [photo] will produce cutouts aligning over one another vertically every third course, while a five-inch shingle offset pattern will produce tab cutouts that align over one another every seventh course. Sketch adapted from Flickinger (2000)[1] [Click to enlarge any image]

You can thus determine the actual pattern in which the shingles were applied to the roof. "Laddering," while permitted by some manufacturers and standards, is a less workmanlike shingle installation and may result in a localized early wear area on a roof.

For laminated or some other shingle designs the offset trim between the shingle courses may be 5 5/8" as we show in this example (below) from CertainTeed Firehalt shingle installation instructiont cited below.

[Click to enlarge any image]

Source & Authority:

• APPLICATION INSTRUCTIONS: LAMINATED SHINGLES [PDF] Certainteed Shingle Appolicator's Manual Supplement, retrieved 2018/02/17, original source: https://www.certainteed.com/resources/FirehaltInstall.pdf

 

Watch out: Ladder-pattern shingle application shows that the roofer liked to work up the roof from one position for as long as possible before moving. Shingles installed in this pattern may be more prone to roof leakage.

Below on a re-roof job in New York you can see, even from a distance, that the roofer is applying the roof shingles in a staggered, not a ladderd, pattern.

A Forensic Engineer's Comments on Shingle Laddering and Asphalt Roof Shingle Wind Damage

Nail Omissions - leaving out some nails - is at fault in laddered shingle blow-offs

James A. Skees, PE

On the photo of the laddering problem submitted by Carl Gerosa of New Rochelle, NY:

I have found that the loose corners are most often associated with the installer neglecting to place the nails at the ends of the shingles when installing the subsequent rows.

It is not necessarily the result of installing the shingles in a straight line up the roof. The same problem will occur diagonally when the nails are neglected (the common term is "three-nailing"). If the nails are all in the right place, the corners generally stay down either way.

Also see Mr. Skees' comments about nailing errors & asphalt shingle cellophane strip removal

at WIND DAMAGE to ROOFS

...

Continue reading at LADDERED SHINGLE FAILURES & WEAR or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see

Recommended Articles

• ASPHALT SHINGLE INSTALLATION - Best Practices
• LADDERED SHINGLE FAILURES & WEAR
• WIND DAMAGE to ROOFS

Suggested citation for this web page

LADDERING vs STAIR STEPPING SHINGLES at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING ROOFING

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