The following are suggestions for proper design, storage, application, finishing, and maintenance of southern cypress siding. These instructions may be more restrictive than some local building codes, but local building codes must be followed when they are more stringent. Southern cypress siding is manufactured to perform under ordinary service conditions when stored properly, installed on structures with proper vapor retarders and ventilation, and finished and maintained in accordance with these instructions.

STORAGE: Southern cypress siding is a quality wood product dried in accordance to the Standard Specifications for Grades of Southern Cypress:

Finish Grades: 15 percent maximum moisture content.

Common Grades: 18 percent maximum moisture content.

Siding material must be conditioned to the local average in-service moisture content before installation, usually between 8 and 16 percent. Store in an unheated structure or under cover until application. Southern cypress siding may be temporarily stored outside if at least 4 inches off the ground and on a fiat, well-drained surface protected from moisture with a shed pack or waterproof cover. Do not seal the unit because ventilation is necessary to prevent condensation and ground moisture absorption, which may cause mildew or mold. Special care should be given to material, which has become wet during storage (i.e., broken units, etc.,) because it may shrink and open gaps at the joints after application.


Moisture Control. It is necessary to design walls that restrict moisture vapor from entering and condensing within the exterior wall cavity. Proper design will ensure the insulation’s thermal efficiency and the overall structure’s performance. Design must provide continuous vapor retarding equivalent to a rating of 1 perm installed on the living space side of the insulation. Vapor retarders are also required on the ground in all crawl spaces and under concrete slabs.

Acceptable products include: 6 mil polyethylene, asphalt impregnated craft or foil-backed insulation (tabs must be stapled to the narrow face of the studs, not to the wide face), vinyl-faced or foil-backed gypsum, sandwich type craft with an asphalt or polyethylene core, or equivalent. Vapor retarding paints are also available for interior walls.

Site Drainage: Slope ground away from structure for a minimum of 3 feet.

Roof Drainage: Incorporate an overhang or drainage system into the structure design to prevent water from running down sidewalls.

Ventilation: Both attics and crawl spaces require adequate ventilation. Clothes dryers must be vented outside; kitchen and bathroom fans are recommended to vent localized moisture outside.

Attics: Attic vents should provide a minimum of 1 square foot of net free vent area for every 150 square feet of attic space. Unrestricted air circulation is best achieved by a combination of soffit vents and ridge or roof vents.

Crawl Spaces: Crawl space vents should provide a minimum of 1 square foot of net free vent area for every 25 lineal feet of exterior wall. They should be placed to allow for cross-ventilation.

Siding Return at Roof (Dormers, etc.): Use flashing, allowing at least a 2-inch clearance between siding and roof-line (see illustration at bottom right). Cut edges of siding must be finished in accordance with finishing instructions described in this guide.


It is recommended to apply southern cypress siding over standard sheathing material with maximum stud spacing of 16 inches O.C. (off-center). Where building codes permit, siding may be applied over unsheathed walls. A suitable building or felt paper wind barrier is recommended and must be used where building codes require.

Foam and Foil-Faced Sheathings: Both rigid foam and foil-faced sheathings can be vapor barriers. Rigid foam sheathings, however, offer little or no resistance to sag caused by the weight of the siding on the nails. For application of southern cypress over rigid foam sheathing, use angular threaded ring shank nails long enough to penetrate at least 1 inch into framing members. For example, siding over 1-inch foam requires a 3-inch nail (10d). Note: southern cypress siding applied over foam sheathing may take on a wavy appearance if the siding is compressed by nailing with too much force.

Installed Siding Material Checklist

Nails: Hot dipped galvanized or stainless steel with 1/4 inch head; nails must be long enough to penetrate 1 1/2 inches in studs; ring shank or thread shank nails provide increased holding power and must penetrate studs at least 1 inch; siding nails should have blunt points to reduce splitting of the siding.

Caulking: Use high-grade, non-hardening acrylic or equal.

Paint and Stain: See finishing instructions.

Drip Caps and Flashing: Must be used over doors, windows, masonry, and other types of siding, and siding returns at dormers.

Corner Boards: Must be used at inside and outside corners (see illustrations at top right).


Preparation: Before finishing, repair all nail holes and surface irregularities. All surfaces should be clean and caulking should be in good condition. Seasoned southern cypress siding should be finished promptly at the time of installation to protect against moisture absorption, discoloration from rain, and mildew. However, under no circumstances should siding be finished when it is wet.

Selection of Primer and Paint: Use a high-quality primer compatible with the paint being used–most paints will require an oil-based alkyd primer. High quality, oil-based paints, is recommended. Certain paints contain water-sensitive polymers and/or surfectants that might absorb moisture, causing the siding to swell or creating an environment suitable for biological degradation. These additives are present in a variety of paints, at different price levels, and their presence is not necessarily reflected on the label. The only safe approach is to use a paint specifically recommended by a paint manufacturer for use on exterior wood siding. Light-colored finishes reflect heat more than dark colors and reduce the possibility of shrinking, checking, warping, and loosening of nails.

Application of Paint: Always follow the primer and paint manufacturer’s recommendations. Priming all sides and edges of wood siding provides superior performance over all types of sheathing. After the prime coat has dried, apply two coats of paint to all exposed surfaces and edges. Brush application is recommended because it provides a more uniform coverage. The time of day, the temperature, dew, fog and rain influence tile quality of tile paint job. Follow paint manufacturer’s recommendations in regard to these factors.

Application of Stain: Southern cypress siding takes stains very well, however, semi-transparent stains do not last as long as paint systems. Most semi-transparent stains will provide adequate protection for 18 to 24 months depending on weather conditions. Consequently, they require reapplication at regular intervals to protect the wood siding from warping, checking, shrinking, and loosening of nails. Where it is desired to leave wood in its natural state, it should be brushed on all sides and edges with a quality clear water repellent preservative, preferably with an anti-fungal additive (See Bora Care). Allow the water repellent to be absorbed and dry to the touch so the solvent will not react with foam sheathing. Clear coating must be re-applied at frequent intervals.


Nail Sizes for Wood Siding over Sheathing

Siding/Sheathing Combinations Recommended Nail Length Recommended Nail Length
(Use wood siding nails) Smooth Shank Ring Shank
3/4″ siding plus 1/2″sheathing 10d (3″) 8d (2 1/2″)
3/4″ siding plus 3/4″ sheathing 12d (3 1/4″) 9d (2 3/4″)
3/4″ siding plus 1″ sheathing 16d (3 1/2″) 10d (3″)


Nailing Methods
Nailing Methods for Cypress