Vinyl siding defect recognition & diagnosis:
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.
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Article Series Contents
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.
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.
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.
[Click to enlarge any image]
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.
Here is what the Vinyl Siding Institute Advises about Installing J-Channel
See VINYL SIDING INSTALLATION for details.
Also see PEEL & STICK FLASHING MEMBRANES for products useful to seal around windows and doors before installing siding
Details about stains on vinyl siding are now found in a separate article at VINYL SIDING STAINS
Common sources of stains on vinyl siding include formation of algae, fungus, lichens, dirt accumulation on damp surfaces, rain splash-up soil, even smoke from nearby barbecues or fires.
More about building wall stains can also be found in these companion articles:
Details about the causes of & cures for leaks in building siding are now
Vinyl Siding is Not Waterproof
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.
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:
Watch out: buckling vinyl siding at the bottom of a wall may indicate hidden structural damage or insect pest damage. Details are in the article cited above.
Detailed specifications for hanging vinyl siding to avoid buckling and blow-offs are found in this article:
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.
Watch out: Information about vinyl products (not just siding) that may produce odors or have other environmental concerns 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
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.
But without a siding replacement tool such as Malco's Side Swiper SRT1 shown in our photo (left), re-hooking the bottom edge of the new siding section to the top of the course below can be almost impossible.
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) has a nicer handle that makes unlocking and re-locking of vinyl siding easier and less likely to be damaged.
Continue reading at VINYL SIDING BUCKLED WARPED or select a topic from the More Reading links shown below.
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Frequently Asked Questions (FAQs)
Question: Chalking surface of older vinyl siding - is this normal
I am wondering why when I rub my fingers across our siding I come away with my fingers being white. Is this a normal vinyl siding thing or does it mean it has been previously painted or what? I want to clean the siding but would like to know what the white stuff is first. - Anon 8/18/2011
Watch out: any older oxidized plastic may have increased in brittleness and be more vulnerable to mechanical damage.
Question: I found carpenter ants behind my siding - how do I fix the problem
after i took down insulation i found a lot of carpenter ants ,killed them . investigated more around the house noticed in the garage that there were more took down sheet rock water damaged. j channel cut and holes with wood showing .how do i fix this? - Dale 7/21/12
Dale you're going to need to follow the water backwards until you've found the leak or water entry point; fix that, and restore the siding; You'll need the "siding hook" siding replacement tool we describe if you're working from the bottom of the wall up.
Question: Mike diagnoses reflected sunlight & heat as a cause of rippled vinyl siding
(Sept 18, 2012) Marc said:
I had vinyl siding installed to replace my cedar siding. They removed the cedar to install the vinyl. The sheathing was gypsum board and while removing the cedar siding, much of it was damaged (holes, tears, etc.). Instead of replacing it, they just covered the sheathing with a thin foam barrier. They also caused additional damage that I was able to find in my attic where they missed hitting studs and blew out holes in the sheathing. Should they have just covered up damage? Is it reasonable to ask them to remove the siding to inspect and repair all damaged sheathing?
Nov 27, 2012) Mike in Michigan said:
[quote]The picture with the dryer vent below the window was caused by the reflection of the sun off the window. I would put $$$ on it. - Jim Hilt 9/11/2011[/quote]
On the contrary! As the sun rises in the sky, the reflected light and heat move downward on the wall. That softening pattern is exactly where it should be. When the window and adjacent wall are so close together (and always facing south and west), no breeze carries the hot air away. Between the direct sun and the reflected sun, you get high temperatures on the surface, but it's rare to see damage from it, because usually airflow cools the surface off. When you put them too close together like this (and again, oriented to the sun just-so), the pocket of dead air allows temps to get even higher and you see the damage shown.
Thanks very much for the excellent analysis of rippling vinyl siding caused by reflected heat from windows. I've added your comments to the article above in the FAQs section.
If you want to be identified as a technical reviewer/editor, contact me using the CONTACT US link.
Question: snow damage to vinyl siding ?
(Apr 21, 2014) Anonymous said:
Does snow accumulation against vinyl siding cause any damage to the siding?
Snow is unlikely to damage vinyl siding. However, melting snow piled against vinyl siding means there is a risk of water penetration into the wall structure - which could be a source of damage: rot, mold, pest infestation.
Question: vinyl siding sealed to concrete slab
(Oct 24, 2014) Pausha said:
The brand new house that we are planning on buying, has the vinyl siding sealed to the very bottom to the concrete slab by mortar. Is that right? Our home inspector thinks that it should have some kind of gap for the water to pass, to avoid water damage. Thoughts?
Pasha your home inspector was on target. Clearance space is to avoid both rot and insect damage.
Question: rain rots door frame, where is the leak?
(Nov 24, 2014) Fred said:
I have a side entrance door to the garage. Rain water is rotting the bottom of the door frame on the hinge side. Where can this be coming from? I already replaced the door frame once.
Fred, that sounds as if there may be both door head flashing and side flashing errors and framing or trim details trapping water in the structure.
Question: siding falls off the house or is easily pulled off
12/11/2014 Amanda said:
Hello. We had vinyl siding installed and now peices have falled off or are bowing out. We had a friend come over who we found out does it as well and he ended up placing two fingers under the siding and pulled and it popped off. IS it supposed to do that?
NO Amanda certainly not. It sounds as if siding on your home was nailed to some sort of soft sheathing such as fiberboard and it missed the wall studs. Better ask an experienced siding contractor to take a look to see what's needed before more blows off.
Keep us posted. Send along photos if you can (see our CONTACT US link) and I can comment further.
Question: cut off the vinyl skirting around a mobile home to cure buckling?
(Jan 2, 2015) ml said:
The idea of sawing off the plastic mobile home skirting is probably missing something more important: the home is sinking; we need to identify the cause and fix it. I suspect that the home was never placed on a concrete slab with a footing nor even on properly-constructed masonry piers. Perhaps it was just set on concrete blocks placed on the ground.
WATCH OUT: a sinking mobile home can break gas lines, plumbing piping, and can tear electrical wiring - any of which can be quite dangerous.
The proper approach is to inspect and repair the supporting piers for the home, if necessary temporarily adding support until proper piers can be built. Inspect the connections to any piping, wiring, etc. that may have been moved or damaged and have any damage repaired.
Quite possibly jacking and leveling the home to get it properly supported will actually result in the home being lifted up a bit - so do not cut or trim any skirting until all of the proper repair work has been done.
Details are at this article about proper support beneath mobile homes
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