Most siding failures occur long before they actually fail. Although there may be cosmetic problems such as fading, buckling or sagging, to most people’s eyes the exterior appears intact. And even though there may be no apparent leaks, there can be much damage to the interior of the wall occurring over three or four seasons before discovery.
Below are several diagnostic items one can check on a walk-around inspection of the exterior of a building as well as some diagnostic thresholds for deterioration and how one might present such findings for action to a building owner.
Moisture intrusion is the signal that outranks everything else
In situations where water appears behind the siding, focus shifts to structure. Look for signs of water intrusion such as staining on exterior surfaces, efflorescence on masonry below siding runs, and persistent dampness at the bottom of the base course of wall cladding. Once the weather-resistive barrier is compromised, individual siding panels must be replaced to return a siding-covered wall to a cosmetically intact condition even though performance has not been restored.
Probing without full demolition
Measure the substrate in various locations around the home with a pin-type moisture meter (PI Mayo check for wood moisture with a finer point). Note the percent reading of sheathing material for a general indication of active moisture penetration through cladding as opposed to normal, seasonal variations in wood moisture content. Note also appearance of softened wood (rot) around edges of siding, such as corners, where fasteners sink into substrate without biting. Scheffler notes that, “if the fasteners spin in the siding, then the siding is too far gone and needs to be replaced.”
Mechanical failure differs sharply by material
Cracking, warping, buckling or delamination are problems which need to be analyzed regarding the materials used for the exterior claddings. Vinyl siding may cup, bow or pull away from a wall. Most of these distortions happen within a short time frame and are caused by fastening or clearance problems. Brittle siding splitting along the nail hem is typically old siding at the end of its useful chemistry life and will continue to split and deteriorate.
| Material | Early warning sign | Point of no return | Practical service life |
| Vinyl | Waviness, loose locking channels | Brittle fracture at fastener slots, color chalking through | 20 to 35 years |
| Fiber cement | Hairline cracks at butt joints | Edge swelling, delamination, failed factory finish | 30 to 50 years |
| Wood lap or shingle | Peeling paint on more than a third of elevations | Rot at end grain, cupping that will not lie flat | 20 to 40 years |
| Engineered wood | Swollen bottom edges | Fiber separation, soft spots when pressed | 20 to 30 years |
| Aluminum | Denting, chalk transfer on contact | Seam corrosion, oxidation through the coating | 30 to 40 years |
Warping as a moisture indicator
However, the exterior surface might cup, bow or even pull away from the wall. This type of failure can appear to be exposed to sunlight but is actually caused by the interior vapor pressure attempting to escape through the siding panels. Unless this vapor issue is addressed prior to a re-side job, the siding panels will likely fail in similar fashion on the newly installed siding.
Fading and finish loss are less trivial than they look
Uniform fading on all surfaces that receive direct sun on the south side is normal aging. However, uneven fading, staining, water soaking, extreme chalking, and any combinations of these are indicative of siding finish failure (coating or color failure). The exterior surface of painted wood or engineered siding products will begin to absorb water into the substrate at all edge areas that are not sealed such as under lap edges, splice joints, butt joints, etc.
It is important to make the distinction between whether recoating will hold and whether recoating is recommended. This is a very difficult thing for a repair service to do. If the existing surface cannot be cleaned and primed back to a sound material surface then paint becomes a short term fix that will have to be reapplied on a shortening cycle, and will in all probability be more expensive than a full replacement in the long term.
Recurring repairs and the cost crossover
Wait until enough data has been collected so that all occurrences of needed repairs can be tracked (i.e. The costs of needed repairs can be added up). A pattern of needed repairs is a capital decision that hasn’t been made yet.
- Number of separate repair events in the past five years
- Whether repairs cluster in one area or appear across multiple elevations
- Cumulative repair spend against current replacement cost
- Availability of matching profile and color for the existing product
- Energy performance complaints from occupants, particularly drafts and uneven heating
One test, If you had to make a similar repair on 3 or more elevations, and it would cost greater than 1/4 of the cost to replace siding of that type on that property, then continued patching is not cost effective. Owners in northern Virginia who reach that threshold are usually better served by getting a scoped estimate for siding replacement in Alexandria than by funding another round of patchwork.
Building the recommendation
It is much easier to ‘sell’ replacement of a failed siding system as a complete ‘assembly’ (siding, weather barrier, flashing and trim) rather than individual components. Siding repairs have a bad reputation. It is much better to charge for the replacement of the siding assembly. Most failed siding systems have similar defects and identifying these can form the bulk of your evidence.
Where inspection intervals should sit
As long as you’re inspecting twice a year (after the first hard freeze of the season and again in late spring) and recording moisture content at specific locations within the building (to track over time), these types of problems can be caught early before they fail and documented as a case for future reference.
