How to prepare and coat exterior timber & trim
Exterior stains, varnishes and paint 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
A professional looking 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. Both water and oil based products can be brushed over surfaces previously coated with oil based stains of a similar shade, as long as the prior coating was applied more than 12 months ago.
| 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. New timber also requires washing to remove waxy deposits, and help remove tannin which may bleed through the coating, 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 280 grade sandpaper to remove minor surface flaw. Always sand in the direction of the grain and remove sanding dust prior to staining. Fill cracks and nail holes with an exterior water based putty matched to the timber tone. Do not use linseed oil putty. | If required, you will need to completely remove the old coating by thoroughly sanding back the surface to bare timber. If your deck has been painted you must remove the coating before oiling or staining. Remember to punch nails before sanding. Always sand in the direction of the grain and remove all sanding dust prior to product application. Fill cracks and nail holes with an exterior water based putty matched to the timber tone. Do not use linseed oil putty. |
Handy Hint
For a smoother finish and better adhesion, remove sanding dust and wipe timber with a rag dampened with mineral turpentine (when using oil based products) or methylated spirits (when using water based products). Allow at least 24 hours drying time before product application.
| Application | Timbershades | Timbercolour | Exterior Varnish Stain & Clear |
|---|---|---|---|
| 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 | The first coat, fully saturating the timber, for a semi transparent finish. Apply a second coat when dry for a fully opaque finish. Do not thin the product – use directly from the can with brush, roller or spray gun. If using a brush, do not load the brush too heavily. Work the stain well out along the surface. If spraying, back brush while stain is wet to ensure an even coating. | With brush, roller or spray gun. On hotter days, the product may require a little thinning with water (no more than 10%) to keep it workable. If using a spray gun, back brush whilst the product is wet to ensure even coating. Apply two coats for opaque coverage and highest durability. | With a good quality synthetic brush for the smoothest application. Apply three liberal coats of either finish for highly durable, attractive results. Applying more coats will result in a higher sheen level. |
| Dry time | Allow 12 hours drying time between coats. | Allow 2 hours drying time between coats. | Allow 3 hours drying time between coats for Exterior Varnish Stain and 24 hours for Exterior Clear. |
