The process of making hardboard into lap siding makes the board edges much more absorbent to moisture than the faces. Rain, melting snow, and condensation run down the face of the siding and collect at the drip or bottom edge. If the edges are not properly sealed, this moisture can be absorbed into the board. The expansion and contraction of the hardboard caused by seasonal temperature changes and moisture absorption create larger spaces in the board which lead to board decomposition and delamination. Other contributors to moisture penetration are areas where nail heads have fractured the board surface and butt ends that were cut and not properly sealed during installation.

Severely damaged boards must be replaced. Some board decomposition can be tolerated, however, these will show as major blemishes on the newly applied topcoat. The use of sandpaper should be done sparingly so as not to break the board surface. Spot priming followed by a full coat of primer is recommended after all traces of surface wax have been removed.

One coat A-100 Alkyd Exterior Wood Primer

Two Coats Exterior Latex House and Trim Paint

Efflorescence

Cause

Efflorescence is often seen as a white fluffy deposit of salt crystals on cementious wall surfaces. It depends on the presence of salt and moisture. The growth of crystals will continue as long as both are present. The salts are present in the mortar blocks or concrete structure and the moisture is usually attributable to some building defect. When emanating from mortar in brick or block buildings, efflorescence will appear as narrow bands corresponding to mortar joints,

Painting should be delayed if efflorescence continues. Salts should be removed by mechanical brushing. The use of water to remove efflorescence will only aggravate the defect. Repair areas where moisture penetrated the wall. Allow walls to dry thoroughly.

Recommended Sherwin-Williams Coating System

One coat Loxon Exterior Acrylic masonry Primer

Two coats Loxon Exterior Acrylic Masonry Paint.

Flaking

Cause

Flaking is the lifting of paint from the underlying surface in the form of flakes.

It is generally preceded by cracking or checking and will occur over different surfaces. When it occurs over wood, it is usually found on those boards that have an excessive amount of "flat" hard grain pattern. This flat grain pattern is smooth, hard, and non-porous. Highly pigmented paints crack and eventually flake when applied to this type of surface. They cannot accommodate the large extremes of expansion and contraction of the wood that are caused by seasonal weather changes. Because of the poor paint penetration into the hard, flat grain, flaking will occur on these areas.

Solution

A light sanding to fresh wood followed by application of a high quality undercoater is recommended. Wood must not be allowed to weather prior to coating. Replace boards that have an excessive amount of flat grain patterns with boards that have an edge grain. (e.g., boards with equal amounts of narrow hard and soft grain patterns).

Recommended Sherwin-Williams Coating System

One coat A-100 Alkyd or Latex Exterior Wood Primer

Two coats Exterior Latex House and Trim Paint

Frosting

Cause

Frosting is the formation of white surface crystals on paint surfaces. When present, these crystals are most noticeable on dark colors and form in areas that are protected from the cleansing action of rainfall. The crystals form when the paint is exposed to excessive moisture (dew, condensation, rain, etc.) or cool temperatures during the curing process and create a surface condition called "frosting."

Solution

Apply paint to all surfaces during climatic conditions that allow proper curing of the paint film. If frosting, use a garden hose to flush crystal formations with warm tap water. Water-soluble crystals will disappear. Follow-up water flushing may be required at later dates and eventually crystal formation will cease. If crystals are not water-soluble, then other actions are required. Allow surface to dry thoroughly . Using medium grit sanding paper, lightly sand crystals away until original color of paint film reappears. Remove all loose dust and apply a uniform coat of A-100 Alkyd Wood Primer. This alkyd undercoater will act as a barrier coat preventing the formation of future frosting. Apply latex or alkyd topcoat.

Recommended Sherwin-Williams Coating System

One "barrier" coat of A-100 Alkyd Wood Primer