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Vinyl siding defect recognition & diagnosis:
Improper installation details of vinyl siding or of vinyl siding F or J channel trim or corner moldings can cause or aggravate building leaks and even invite insect pests and structural damage.
This article discusses common defects observed in vinyl exterior building siding, such as buckling, splitting,
cracks, odors, and questions about the need for a vapor barrier behind vinyl siding and over building sheathing.
Included are comments from several recognized building inspection and construction authorities.
Our page top photo shows wrinkled vinyl siding - often caused by heat exposure such as from a BBQ Grill - but in this location the pattern and size of the damage made us suspect that there was another cause.
Inspect Vinyl Siding for Damage: Examples of Bad Installation, Cracks, Leaks & Other Damage to Vinyl Siding
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While some vinyl siding on the home shown above has been replaced (darker siding at green arrow) this was one of the worst vinyl siding installation jobs I've seen.
At this New York hoome the siding has at some locations been installed using scraps (pink arrow), with gaps (black arrow), with lower corner trim on the outside rather than inside of the upper corner trim segment (leaky at pink arrow), buckling (tan arrow), with un-even, overlapped courses (blue arrow), perhaps where the siding was installed below a now-removed porch roof that has been left poorly-flashed as a possible wall leak (red arrow).
This article discusses vinyl siding inspection points, defects, and repair procedures.
Most of the vinyl siding problems we see appear to be due to poor installation details, though on occasion we see cracks and breaks that may be blamed on older, more brittle vinyl products.
Our photo (above left) demonstrates impact damage to vinyl siding, in this case just above the floor of an outside deck.
Our second vinyl siding damage (above right, courtesy of Carson Dunlop Associates) demonstrates an impact damage even to siding that made both a hole and a crack in the wall covering. With (often older-generation) more brittle vinyl wall siding products we often find impact damage and holes caused by stones kicked-up against the wall by a lawn mower or weed-wacker.
Vinyl Siding Gaps & Holes Caulked; Cracks at Vinyl Window Trim
Our vinyl siding caulk photo (above left) shows a combination of improper trim installation, building leaks, caulk where it is not helping, and even the caulk was so sloppily applied that it didn't seal anything.
Our photo at above right shows cracking vinyl siding above a window corner - a bad place for a leak that can lead to building water entry, window damage, and even hidden mold.
Improper J-Channel in Vinyl Siding Cause Costly Building Damage
One of the most common vinyl siding installation mistakes (also found on aluminum sided buildings) is the improper cut and trim of the ends of horizontal J-channel used above windows and doors (shown at below-left), or improper termination of the bottoms of J-channel used along the sides of windows or doors (shown at below right).
A simple error such as short-trimming of the J-channel and failure to provide proper water-directing bends can send water behind the J-channel and into the building wall and structure.
In our photo at above left it looks like really sloppy J-channel work during siding installation, leaving a leak at the window sill. The required tab extension on the horizontal or upper J-channel is missing entirely, allowing J-channel rainwater to flow down behind the vertical J-channel along the window side.
In our vinyl siding J-channel photo at left it appears as if the window-top horizontal J-channel end cut tab was correctly cut and bent over the outside of the vertical J-channel running along the window side. A reader provided this detail during investigation of leaky vinyl siding that is illustrated and discussed at SIDING LEAK DIAGNOSIS & REPAIR.
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Watch out: J-Channel errors can rot windows and doors: Our photo of improperly-cut J-channel trim around a window (above right) shows a more serious problem than may be immediately apparent. In Spackenkill, Poughkeepsie, NY we found an entire neighborhood of homes in which nearly all of the windows were rotted beyond repair due to this error.
Wind-blown rain sent inside the J-channel trim and into the window structure was the problem caused because the installer didn't follow the manufacturer's instructions. Properly the top J-channel is trimmed to include a tab bent over the vertical J-channel to route water outside, not inside the trim.
See Figure 1-25 in Best Construction Practices for details, and return here using your browser's "Back" button.
Here is what the Vinyl Siding Institute Advises about Installing J-Channel
J-channel is used around windows and doors to receive the
siding. Follow the steps below when applying trim.
Cut and bend the tab of the top piece of J-channel
down to provide flashing over the side J-channel.
[This instruction pertains to J-channel run above windows and doors. Omission of this detail is a very common mistake that leads to leaks in and around windows - Ed.]
Fold the bottom end of the side piece of J-channel inward at the bottom of the window, to fit
over the existing J-channel to prevent water from entering under the sill.
Cut the side J-channel members longer than the height of the window or door, and notch the
channel at the top.
Figure 33 [in the original document].
Miter cut the free flange at a 45° angle and bend the tab down to provide flashing over the
side members (Fig. 34) [in the original document].
A similar miter and tab may be provided at the bottom of the window,
depending on the sill’s condition. The J-channel should fit snug to the window. - The Vinyl Siding Institute, Website: http://www.vinylsiding.org/Email: firstname.lastname@example.org, - retrieved 9 Feb 2015, original source: http://www.vinylsiding.org/wp-content/uploads/2015/01/I1_Vinyl_Siding_Installation_Manual_English.pdf
Watch out: vinyl siding used on building exteriors is not nor is it meant to be a waterproof barrier. While the actual face of vinyl siding is waterproof, a vinyl sided building wall is by no means waterproof.
Openings at the lap joints of vinyl siding sections as well as drain openings provided along the bottom edge of most vinyl siding products let the wall system breathe and allow wind-blown rain that may enter the siding to drain out of it as well.
Below our photographs show what happens to loose, poorly-secured vinyl siding on a home. These pictures were taken just about a year apart. We had watched the loose buckling siding on this Poughkeepsie NY home for some time. Finally after a windstorm much of the gable end siding has simply been lost completely.
Below are additional examples of poorly-attached siding (below left) and siding that was literally pulled off of the building when an adjoining stucture itself collapsed. The consequences of the failure at right were more serious than met the eye: this wide opening into the building wall allowed rain to soak the wall interior, leading to costly mold, rot, and insect damage to the structure.
In our photo at above left demonstrates a loose siding panel that is inviting more serious wind damage. Our second photo (above right) demonstrates a combination of poor siding installation, improper lower-roof flashing, a home that sat for months unattended while wind, rain, and snow penetrated the structure. These are almost certainly construction and installation defects, not product defects.
Causes & Cures for Damaged Vinyl Siding: Bent, Buckled, Rippled or Sagging Vinyl Siding
Vinyl siding that buckles due to improper nailing (photo shown above left) is is not normally extremely wrinkled, and will be more wavy across longer horizontal runs of surface.
A Complete Guide to Causes of Rippled, Buckled, Bent Vinyl Siding is at:
As our buckled vinyl siding at ground photo (above left) and Carson Dunlop's photograph vinyl siding photo shows (below left), bringing vinyl siding down to ground contact or even below ground may please the architect or home owner's sense of aesthetics, but it is an engraved invitation to wood destroying insects to attack the structure.
We like to see 6-8" of clear foundation wall between the bottom of wall siding and the top of the ground surface. Adding mulch as was done here, increases the invitation to termites.
Vinyl Siding / Plastic Odors, Emissions, Health Information
Watch out: Information about vinyl products (not just siding) that may produce odors or have other healh risks, fire risks, and environmental concerns that can be found at
How to remove vinyl siding: This Siding Hook is Key if you Need to Remove or Reinstall Part of a Vinyl-Clad Wall
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Shown above is a siding hook, also referred to in some manuals as a zip tool.
As Steve Bliss points out at VINYL SIDING LOCK & NAIL FLANGES, all vinyl siding panels have a locking
tab at the bottom of each panel that snaps over the top tab
of the panel below.
It's not unusual to need to re-hook loose vinyl siding such as shown in our vinyl siding damage photo above, or to remove impact-damaged, heat damaged, or badly stained vinyl siding from a structure. In fact we might try removing and re-nailing vinyl siding on a building wall that buckles every time the sun shines on it. Brute force can un-hook vinyl siding in the middle of a wall from the course below and course above, in order to pull nails and take off a bad siding section.
Watch out: trying to tear off vinyl siding without unhooking the lower edge (buttock) of each siding course from the course below risks damaging more siding courses and increasing the cost of repair or replacement of the wall cladding. In fact, without a siding replacement tool such as Malco's Side Swiper SRT1 shown in our photo above, even if you can tear off the siding, re-hooking the bottom edge of the new siding section to the top of the course below can be almost impossible.
5 Steps in Using a Vinyl Siding Zip Tool or Un-Lock Tool
Below at left we illustrate how the vinyl siding hook can be used to "un-hook" the lower edge or "buttock" of vinyl siding in order to remove the siding for repair or replacement of damaged siding or to permit replacement of damaged corner trim or window trim or J-channel against which the vinyl siding is abutting.
At above right we illustrate the names for the parts of a course of typical vinyl siding. This illustration was adapted from the helpful vinyl siding installation manual provided by the Vinyl Siding Institute cited below.
The hook on this tool is designed to loosen and then help re-lock the bottom edge of vinyl siding without cutting or damaging the siding. A few home inspectors also carry this siding replacement tool to permit invasive inspection of a building wall - something not normally done during a visual home inspection for a purchaser.
A newer version of this tool, the Malco SideSwiperII (SRT2) (see REFERENCES) has a nicer handle that makes unlocking and re-locking of vinyl siding easier and less likely to be damaged.
To use a siding unlock or zip tool, start removing siding by un-hooking the siding course immediately above the damaged siding.
Simply insert the hook end of the tool into the locking flange in the buttock or lower edge of the vinyl siding (see sketches below).
When the hook catches the up-facing lip of the siding buttock, pull downwards on the tool. The siding will un-hook from the top nailing flange of the siding course immediately below. This gives ready access to the nailing flange of the lower course.
Use a small flat bar to pry out the nails in the nailing flange of the vinyl siding course to be removed. If the siding was nailed properly in its original installation the nails should not be tight against the siding or wall, so a thin flat bar will work nicely to remove them. Be sure that the butt of the flat bar presses against the nail flange or the wall sheating above the nail. Don't put the butt of the flat bar against the raised ridge of the nailing flange or you may damage it.
If the siding panel being removed is very brittle or badly damaged such that its nail flange has been broken or can be broken away from the wall sheathing, you can opt to leave the nails in the wall: just remove any fragments of the old siding behind the nails and then drive the nail flush with the wall surface.
Remove and replace the damaged vinyl siding.
Watch out: you may find that even if you are using stored "new old stock" vinyl siding from the original siding batch that was installed on the building the color of the new siding may not be a perfect match with the older siding remaining on the wall. Depending on the siding color and specific product, some sun-fading is normal. The photo of a horrible vinyl siding installation job shown below illustrates a color mismatch that was probably unavoidable. But the other bad siding work discussed starting at VINYL SIDING INSPECTION & REPAIR could have been avoided.
How to Remove & Replace Thick, Non-flexible Vinyl or Polycarbonate Siding Panels
CertainTeed and other manufacturers note that when removing thicker non-flexible vinyl or polycarbonate siding panels such as that company's Cedar Impressions Panel, to remove the old panels you will need to use a wood chisel to locate the locking tab of the old panel and to literally break it off.
The siding zip tool shown above won't work as the thicker plastic panels are not flexible enough to simply pull down and un-hook. The company provides a panel replacement kit that includes new cam clip and snap rivet fasteners to hold the replacement Cedar Impressions Panel in place. Or alternativel colored trim nails can be used to secure the new panel in place.
Where to Download Vinyl Siding Installation Manuals
Your local vinyl siding supplier or building supplier will be happy to give you the vinyl siding installation manual for the specific product you are purchasing, as everyone involved has an interest in a proper vinyl siding installation. If your supplier is out of manuals for their product just give the manufacturer a call or check their website for a down-loadable vinyl siding manual. Here are some sources of vinyl siding installation guides:
VINYL SIDING INSTALLATION - online guide from expert Steve Bliss, this article offers practical tips and general vinyl siding installation advice. " Vinyl Siding: Product Choices & Proper Siding Installation Details, vinyl siding defects & repair advice"
Beck, David H., Robert D. Shaw, and David J. Stucky. "Temperature-expansion indicator for siding panels." U.S. Patent 6,939,036, issued September 6, 2005.
A temperature indicator for a siding panel senses panel temperature and indicates on a graphic scale the corresponding effect of thermal expansion over differences in temperature. The temperature indicator can be various forms of contact thermometer, temperature strip or sensor and can be integral or temporarily affixed during installation or for later assessment for correct panel gapping. The indicator shows how closely the edge of the panel can be placed to an adjacent surface while avoiding interference over a range of thermal expansion temperatures.
CertainTeed, "Installation Guide, Vinyl and Polymer Siding",[PDF] CertainTeed Saint-Gobain Corporation, Tel: 1-800-233-8990 (USA), Website: www.certainteed.com/mastercraftsman, retrieved 2015/10/30, original source: http://www.certainteed.com/resources/cts205.pdf
Georgia-Pacific, "Vinyl Siding & Accessories Installation Guide" [PDF], Georgia-Pacific, Website: http://www.gpvinylsiding.com/, retrieved 2015/10/30, original source: use the website link given at left.
For best results, it is recommended that vinyl siding meet the requirements of the Vinyl Siding Institute Sponsored Certification Program. See www.vinyl- siding.org for a current list of certified products. This manual sets forth the basic guidelines for vinyl siding installation.
The instructions herein are based, in part, on ASTM Specification D4756, the standard method for installation of vinyl siding and soffit. Updated information has been added as necessary. Additionally, it is recommended that installers review applicable building codes for variations that may apply to specific products or geographic areas.
CERTAINTEED, VINYL and POLYMER SIDING INSTALLATION GUIDE [PDF], CertainTeed Saint-Gobain Corporation, Tel: 800-233-8990, Website: www.certainteed.com/mastercraftsman, includes "Top Ten Tips for Installing Vinyl Siding", retrieved 2017/09/13, original source: https://www.certainteed.com/resources/CTS205.pdf
Fire Safety Information Excerpt:
To the Building Trades, Specifiers, Professionals and Do-It-Yourself Installers: When rigid vinyl siding is exposed to significant heat or flame, the vinyl will soften, sag, melt or burn, and may thereby expose material underneath.
Care must be exercised when selecting underlayment materials because many underlayment materials are made from organic materials that are combustible. You should ascertain the fire properties of underlayment materials prior to
installation. All building materials should be installed in accordance with local, state and federal building codes and fire regulations.
Vinyl Siding Institute, "VINYL SIDING INSTALLATION MANUAL", [PDF] (VSI), National Housing Center, 1201 15th St. NW, Suite 220, Washington D.C. 20005, Website: www.vinylsiding.org, retrieved 2015/10/30, original source http://www.vinylsiding.org/wp-content/uploads/2014/02/I1_-_Vinyl_Siding_Installation_Manual_English2.pdf retrieved anew 2017/06/10 and uploaded in a compressed format for faster download by readers, no loss of data no loss of image quality - Ed.
Reader Question: is it possible to avoid damaging vinyl siding when replacing broken corner trim?
29 October 2015 Tony Goszulak said:
Is it possible to not destroy the siding or trim corner when replacing the broken corner trim? The siding is existing and the corner was damaged next to a deck.
As a fellow whom I admire, instructor and home inspector Mark Cramer (Tampa) says: "... well, it depends"
Older vinyl siding may be quite brittle and hard to work-on without damage. Our photo above shows broken vinyl corner trim on a vinyl sided home in Glens Falls, New York. Your corner trim may look like that. The good news is that most vinyl siding can be removed, handled, or pieces replaced without breaking it.
Work carefully using a special tool to unlock the clipped-together bottom edge of the siding. I have added a photo of the siding unlock tool into the article above.
Then using a small flat bar or a pair of them, remove the siding nails holding the siding in place.
Remove enough siding nails to remove or loosen the siding end enough to expose the nails holding the vertical vinyl corner trim in place.
Remove and replace the corner trim as needed.
Re-fasten and re-connect the siding.
Continue reading at VINYL SIDING BUCKLED WARPED or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
Questions & answers or comments about Vinyl Siding on Buildings, Installation, Inspection Methods, Defects, Diagnosis & Repair.
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ASTM E2112, Standard Practice for Installation of Exterior Windows, Doors and Skylights includes flashing details important for vinyl and other siding installations
Vinyl Siding Installation Manual, [PDF] The Vinyl Siding Institute, Website: http://www.vinylsiding.org/Email: email@example.com, - retrieved 9 Feb 2015, original source: http://www.vinylsiding.org/wp-content/uploads/2015/01/I1_Vinyl_Siding_Installation_Manual_English.pdf
Excerpting from the associations's website: The Vinyl Siding Institute, Inc. (VSI) is the trade association for manufacturers of vinyl and other polymeric siding and suppliers to the industry.retrieved 9 Feb 2015, original source: http://www.vinylsiding.org/resources/vinyl-siding-installation-manual-2/
Steve Bliss's Building Advisor at buildingadvisor.com helps homeowners & contractors plan & complete successful building & remodeling projects: buying land, site work, building design, cost estimating, materials & components, & project management through complete construction. Email: firstname.lastname@example.org
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.
Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com
Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: email@example.com
"Weather-Resistive Barriers [copy on file as /interiors/Weather_Resistant_Barriers_DOE.pdf ] - ", how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: firstname.lastname@example.org. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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