It is easy to look at siding installation and perceive that it is easy work to perform well for thirty years or so, but in reality, how well a wall of siding will perform for thirty years or fail at the fastener line in eight years is decided before the first piece of siding is installed. Here is how a competent crew completes the work to complete a clean job to prepare for a possible callback.
Tear-off and what the sheathing tells you
Removal of old siding starts from the top and works down. Most siding systems lock together downward. Therefore, if you were to start from the bottom and try to pry a panel off, you would most likely end up tearing the above panels. Vinyl sided homes can be removed rather quickly with the proper unlocking tool. Fiber cement and older wood lap siding require more care to remove around windows and siding transitions as there are often nails in these areas that go all the way through the siding and into the wall flashing.
The worst part of an enclosed wall is the unknown condition within the wall. When we open up a wall to install siding, we have one chance to inspect the framing, sheathing, insulation, windows, etc. Within the sheathing, look for darkening of the sheathing material at the sill plate area and look for rust stains at the bottom of window corners. Also look at the fastening pattern to see if there have been any prior repairs and see if the insulation has settled or collapsed within the cavity.
Deciding between repair and replacement
A decaying sheathing surface may still be just fine as long as the fibers are still solid and it will hold the siding’s fasteners. On the other hand, if the sheathing won’t hold a nail or is delaminated over a large surface, it needs to be completely removed and replaced as full panels.
Wall preparation that actually matters
Most scheduling problems and costly warranty repairs occur in preparation. Your wall must be clean, dry and strong before you begin covering it up with siding. It will “show” every imperfection of your wall’s surface.
- Pull every remaining nail and staple rather than driving them flush, since proud fasteners puncture the barrier later.
- Check plane with a long straightedge across studs and shim where deflection exceeds roughly a quarter inch over eight feet.
- Confirm that window and door openings are square and that existing flashing laps correctly over the material below it.
- Verify moisture content in replaced sheathing before closing the wall, not after.
- Re-establish or install kickout flashing wherever a roof edge meets a vertical wall.
Weather barriers, drainage, and the gap behind the panel
Remember that the water resistive barrier (WRB) or ‘weatherproofing’ layer is a drainage plane, and not a raincoat. Therefore, if water does penetrate behind the cladding it must be able to run down and out, through the laps of shingle, fully closed taped seams, and a suitable flashing at the lowest point of down pipes, soil & vent pipes, gutters, and eaves, etc. That directs water away from the building’s walls.
Detailing penetrations through siding to guarantee good water penetration resistance in these areas causes by far the majority of failure of an otherwise perfectly completed siding job. Sill pans at openings, head flashing at tops of openings, etc., and sealed laps around pipes, hose bibs, etc. Testify to a very competent completion of a siding job. Anyone gathering bids for siding installation in Allentown is well served by asking each crew to walk through exactly how they intend to flash these details before any contract is signed.
When to specify a rainscreen
| Assembly | Best suited to | Main trade-off |
| Barrier direct to sheathing | Dry climates, vinyl with built-in drainage channels | No drying path for absorbed moisture |
| Drainable wrap or matrix | Moderate rainfall, retrofit where trim depth is fixed | Thin cavity clogs if debris enters at the base |
| Furred rainscreen, 3/8 in or more | Wind-driven rain, wood and fiber cement cladding | Added cost, window extensions, longer fasteners |
Installation and finishing
The lower course of panels should be installed level to the roof line, and checked against it. Siding that is installed on sloping foundations will taper down as it goes up the wall, and be obvious by the time it reaches the eave. All courses of panels should have consistent exposure, with staggered joints between courses, and installed with fasteners in accordance with the siding manufacturer’s nailing pattern.
Siding fasteners must be installed in such a manner that they allow for expansion and contraction of siding materials. Vinyl siding must be installed with siding hung loose enough on fasteners for panels to move with temperature changes. Typically nails are to be driven in the center of the slot of vinyl siding products, leaving roughly the thickness of a dime under the head of the nail. Fiber cement siding is to be installed with siding fastened tight but not countersunk. The preferred method of fastening is blind nailing where exposure allows.
Trim, sealant, and the final walk
Last details, Inspect for proper engagement of lock siding panels, close out vents, pipes, etc. With proper flashing, and check for proper clearances at grade and on the roof surface. Coat all butt joints with sealant to exterior of corner posts, J-channel, etc. Except for the bottom of exterior surfaces of siding.
A clean site at close-out is critical to finishing well on a siding job. Sweeping up with a magnetic sweep, disposing of cut-offs properly, and taking complete photos of all concealed work ensure the client knows what was done to complete their job, and provide excellent defense against future questions two years down the road.