How to prepare and coat exterior decking

Exterior decking and outdoor furniture application guide

1. Before you start

The starting point is to decide what kind of finish you want? Once decided, refer to the Exterior Timber Product Guide to determine which product you need, and the Product Calculator to determine how much you will need to complete the job. Remember that the timber type will affect how much product is required e.g. softwoods can reduce coverage rates by up to 50%. Also, remember to collect the appropriate equipment before you start.

2. Preparation

The end result with your decking and garden furniture finish depends on how well you prepare the timber. Preparation not only speeds up the application of your stain, clear or paint, but also lays a sound base to ensure long lasting results.

Preparation	New timber	Weathered, grey, or previously coated timber
Clean	The surface must be dry and free from any traces of dust, dirt, wax, grease and oil. Use a scraper to remove grease and dirt deposits.
Scrub	With Deck Clean to clean and de-oil the surface of the timber. Timbers with high tannin content (e.g. Merbau, Jarrah) may also require washing to remove tannin deposits, which can bleed through the coating. Waxy, oily timbers (e.g. Cypress Pine) should be washed to remove any build up that may inhibit product penetration. As a concentrate, Deck Clean needs to be diluted – refer to the instructions on the container. Protect garden beds with drop sheets. Leave for no more than 15-20 minutes and wash off thoroughly. Ensure timber is completely dry before coating so product can penetrate properly.	With Deck Clean to remove grey, loose fibres, mould and algae, tannin bleed, and to revitalize the colour of the surface of the timber. If sanding, wash beforehand with Deck Clean so any mould and dirt is not pushed back in to the timber in the process. As a concentrate, Deck Clean needs to be diluted. However it can be used undiluted as a spot cleaner for difficult stains. Refer to the instructions on the container. Protect garden beds with drop sheets. Leave for no more than 15-20 minutes and wash off thoroughly. Ensure timber is completely dry before coating so product can penetrate properly.
Sand	If sanding is required, use a drum or belt sander. Always punch nails before sanding and fill holes using an exterior grade water based putty matched to the colour of the timber. Do not use linseed oil putty. Start with medium to coarse sandpaper (eg. 50 – 80 grade), finishing with a finer grade paper (eg. 150 grade). Always sand in the direction of the grain and remove sanding dust prior to oiling or staining.	On previously stained decks and garden furniture where you wish apply Natural Decking Oil for a semi-transparent, oiled finish, you will need to sand back to bare timber. You can apply a top up coat of Decking Stain to a previously stained deck if the surface is sound. If your deck has been painted, you must remove the coating before oiling or staining (see below). Start with medium to coarse sandpaper (eg. 50 – 80 grade), finishing with a finer grade paper (eg. 150 grade). Always sand in the direction of the grain and remove sanding dust prior to oiling or staining. Fill cracks and nail holes with exterior water based putty matched to the timber tone. Do not use linseed oil putty.
Previously Painted Surfaces	Not applicable	If coating with Timbercolour, remove any loose or flaking paint by sanding or scraping. To test if the surface is sound, cut an ‘X’ through the old paint with a sharp blade. Press adhesive tape firmly over the incision and rip the tape off. If the paint peels away with the tape, the old paint has perished and should be removed. Mould and algae affected areas also need cleaning with Deck Clean.

Application	Natural Decking Oil, Aquadeck & Decking Stain	Garden Furniture Oil
Stir	Thoroughly with a broad, flat paddle (using a scooping action), before and during use. This keeps pigment evenly dispersed in the product during its application, maintaining colour uniformity.
Apply	With a brush: load the brush and remove excess on the can rim. With Cabot’s Decking Applicator: press out excess on paint tray ridges. Start application away from an edge or wall to avoid accumulation in corners, or dripping off edges. Brush or sweep pad evenly along the grain, the full length of 2 – 3 boards at a time. Brush the finish well into the boards, as you go. Don’t apply too much finish, leaving it to pool, as this will dry with ‘high spots’, inhibiting absorption of the next coat. Keep a wet edge to avoid lap marks and double coating. Do not stop mid way along the board. Work so that you are always heading towards a natural break such as a join in the timber, or a corner. Lay off product by brushing gently back over the grain.	Apply liberally with a brush to all surfaces, including exposed edges and end grain. Allow product to soak in to timber for several minutes, then remove excess by back brushing. Apply a second liberal coat, following the same process. Re-apply when timber starts to fade due to weathering, or when water repellency begins to diminish.
Dry time	Allow 18 hours drying time for NDO, 3 hours for Aquadeck and 24 hours drying time for Decking Stain between coats	Allow 24 hours drying time between coats

Timbercolour application for decking & outdoor furniture; if painting your decking or furniture with Timbercolour, follow the instructions in the Exterior ‘How To’ guide. In addition, apply a minimum of two coats, taking care to seal the end grain to prevent rotting and water damage. With white or pastel colours over dark, tannin rich timbers, a third coat may be necessary to reduce tannin bleed through the coating.