What is a Deck Sealer / Sealant?

Wood decks are an added feature to beautiful homes. However, continuous exposure to extreme weather conditions would lead to deck problems like cracks, raised grains, wood decay, and fungal growth. To keep all these at bay and to enhance the longevity and durability of the wood decks, proper care and maintenance like applying stains, sealers and other finishes is required.

The sealants (depending on how they work on wood) can be broadly categorized into Water Repellants (WR) and Water Repellant Preservatives (WRP). A Water Repellant Preservative is a Water Repellant with mildewcide or preservative added to the formulation.

Types of sealants - Details -

The types of sealants in the above mentioned categories can be listed as -

1. Open Finishes - They are least expensive, least effective, purely 'color coats'. Being soft with a minimal surface build, they provide limited or no protection from absorption of water or chemicals, against wear. Though they allow escape of absorbed moisture, they give no protection against spills. These are 90% water and remaining are color and binder to hold together. 'Latex Semi-Transparent Stain' is an example.

2. Closed Finishes - They are not suited for exposed wood like decks and sidings, because though they are chemical resistant and water repellant, their upper surfaces are closed and they trap moisture leading to wood decay. They are usually hard and glossy, are not elastic, don't penetrate effectively, leading to loosening of the surface. Varnish and Polyurethane are the examples.

3. Microporous - They are the 'perfect finishes'. Also called as 'penetrating sealers', they help in long-term preservation of wood. They allow the wood to breathe and allow the escape of moisture from beneath the surface. Acrylic Blends fall in this category.

Tips on sealants -

Clear liquid sealants sealants are long lasting and economical to produce, but allow mildew growth underneath the surface. They should be avoided for the exteriors as they are completely closed, can't be removed or over-coated. One needs to pay attention to contents of the sealers while buying one. Most advertised wood sealers are 95% mineral spirits and 5% alkyd resin. It is advisable to go for the good quality high resin content sealers, as the sealers with only 5-10% solid content are not very long lasting.