The majority of siding failures are not immediately visible. Staining at the bottom of a window or a soft spot in the sheathing may not appear for years, and often it is not the material that has failed, but rather the installation as a whole. The installation consists of several layers and interfaces, and if any of these fail, water will enter the wall and cause damage. Most damage is caused by moisture, and it has to move behind the siding for several years before damage becomes apparent.
While different siding products have different lifespans, the most critical factors to ensuring that your exterior walls last the long haul are the installation decisions made by your exterior contractor and how you specify siding. These are the key factors to ensuring a durable exterior envelope that can withstand the test of time and numerous wetting and drying cycles over the next twenty years.
Workmanship is the variable that actually controls moisture
On a sided wall, water management depends on 3 things, 1) A proper drainage plane (be it behind the siding or between the structural sheathing and the exterior surface of the wall), 2) A proper drainage gap (if the siding is not of a solid nature, a solid skin in contact with the weather resistive barrier, also referred to as a weather barrier or WRB, would fail very quickly in most climates), and 3) Properly shingled flashings at penetrations.
Most of the major defects found in relatively new walls would have been found and fixed during a normal inspection during construction. Most major defects are caused by simple mistakes that any competent tradesperson would understand are wrong. Reverse laps at horizontal joints, housewrap not overlapped at head joints, no kickout at roof/wall junctions and sealant used instead of a proper mechanical detail to close penetrations are all easily avoidable by anyone with an understanding of the principles of weather tightness and drainage through the exterior envelopes that they build.
Fastening and movement tolerance
Many long-term problems with vinyl siding and fiber cement siding are caused by overdriven nails. Vinyl siding needs to ‘float’ on the nails, which means that the nails must be centered in the siding panel’s slot. There must be about 1/16” of play behind the nail head. Fiber cement siding also needs to be nailed into studs, but it can be nailed solidly. However, to allow for thermal expansion, there must be clearance between the siding and roof, decks and grade (ground level). Buckled siding or cracked butt joints or pulled nails all create water entry points.
Reading product warranties for what they exclude
Most siding manufacturer warranties cover only material defects and only for a specific time period. Many have a ‘full coverage period’ at the beginning and then prorate coverage for the remainder of the warranty period. Most exclude labor and have very specific provisions that define an acceptable installation. These provisions must be strictly adhered to to ensure that all claims are covered under warranty.
Claims tend to be triggered by an inspection of the work to confirm compliance with specified clearances, fasteners, joint details and flashing details. Installation images are the cheapest form of insurance on any siding job and should be required as part of the contract scope prior to commencement.
| Cladding | Typical service life | Main failure mode | Maintenance interval |
| Vinyl | 25 to 40 years | Impact cracking, fastener binding | Wash annually, inspect joints |
| Fiber cement | 40 to 50 years | Edge wicking at unsealed cuts | Recaulk and touch up every 7 to 10 years |
| Engineered wood | 30 years | Moisture uptake at butt joints and bottom edges | Repaint every 8 to 12 years |
| Cedar | 30 to 50 years | Cupping, finish failure on south elevations | Refinish every 4 to 7 years |
| Metal | 40 to 60 years | Dissimilar metal corrosion at fasteners | Rinse and inspect every 2 years |
Scope definition and tear off decisions
Deciding to do an overlay or a full tear off of the existing siding is a big part of the risk of any siding replacement project. And as I mentioned earlier, there are many hidden problems with the existing siding. While an overlay is the quickest and lowest cost method of siding replacement, it hides many problems and will need to be replaced in the near future with the proper installation of a weather resistant barrier and other required components. The tear off method of siding replacement exposes the sheathing and will reveal any existing problems with the siding.
A defensible scope for a siding project includes the following items before a final price is established.
- Sheathing condition, with an allowance for replacement priced per sheet
- Window flashing strategy, including whether existing units stay in place
- Drainage gap method, either furring strips or a drainage mat
- Grade clearance and any required regrading or hardscape adjustment
- Treatment of roof to wall intersections and deck ledgers
We bring up these issues before we start pricing, and we hope that your company will bring up these same issues before you agree to a contract. If you are weighing bids in northwest Ohio, ask any siding company in Toledo Ohio to put those allowances in writing, because it is best to bring up these potential problems before you start to tear off the siding.
Communication during the open wall window
Deciding on what happens between the time that the old siding is removed and new siding is installed is critical. Agree in advance who will authorize additional repair work, who will take photographs to record the work and how quickly the wall can be dried in overnight. These are issues that can be easily agreed upon over the telephone and then forgotten. Verbal agreements on a wet Friday afternoon are how scope disputes start.
Aftercare that protects the investment
Handover to Client, Manufacturer’s documentation relating to finished exterior products, schedule of fasteners and sealants used, and maintenance requirements in terms of frequency and duration for completed exterior works. Carry out an annual external inspection in less than 1 hour and focus on sealants at penetrations, check for adequate clearance at ground and roof level interfaces and look for any staining that may indicate water is departing from the exterior envelope at some place other than roof drainage points.
- Check sealant joints at trim, penetrations, and transitions
- Confirm weep holes and drainage gaps remain clear of debris and paint
- Verify grade, mulch, and plantings have not crept above the clearance line
- Photograph any movement at butt joints for comparison the following year
Minor problems that can be fixed with little expense if caught early but become a major tear off and replace of sheathing if left to deteriorate.
