Redwood Deck Sealing Problems

Wood Preparation

• Before applying sealants to redwood decks, clean the wood. The penetration of sealers is increased up to 25 percent when the wood is cleaned first, even if it is new. Except for redwood, wood can be cleaned with an oxygen bleach solution. Since oxygen bleach is prone to darkening redwood and most people prefer to retain its natural color, use oxalic acid -- a solution available at hardware stores and home improvement centers -- to clean it.

Sealant Ingredients

• Many wood deck sealants include protective resins with ingredients such as linseed oil, Tung oil, vegetable oil and animal fat. Avoid sealants with these components as they promote the growth of algae and mildew or contain poisonous mildewcides and fungicides to deter bacterial growth. Sealants made from synthetic oils and resins are impervious to mildew and algae. For best results, use a sealant with color added to it as the pigmentation provides additional protection from the UV rays of the sun.

Sealant Colors

• Sealants come in four varieties: transparent, semitransparent, wood-toned and opaque. Transparent sealants let the wood slowly fade to a rustic, weathered light gray concurrent with protecting it from water and sun. Semitransparent and wood-toned sealants add minimal color to the deck but still let the grain show through. Opaque sealants are best for older decks with flaws and stains in the wood, as they conceal imperfections but cover up the wood grain. The darker the sealant, the more it will show wear and tear and need more frequent reapplication. Clear or light sealants require reapplication every few years while darker ones normally have to be resealed every year. Dark-colored decks absorb and retain more heat than light-colored ones, which makes walking barefoot on them uncomfortable.

Temperature Effects

• Cleaning redwood decks and applying sealants in cooler weather prevent the cleaning solution from evaporating too quickly and help the sealant more easily penetrate the wood. Temperatures between 60 and 70 degrees Fahrenheit give the sealant time to soak into the wood before it is evaporated by the sun. Strong winds also deter the effectiveness of the cleaning and sealing processes.