How to Paint Exteriors
Wall Surface Preparation
Step One - Preparation
The golden rule of DIY - preparation - applies to outside work too. It'll pay off in the long run because results will look better and last longer.
Stripping paint back
Test your paintwork in several areas by cutting a small cross with a knife and pressing adhesive tape across the cut. Then, rip the tape away. If paint comes with it, the paintwork needs to be stripped back to a firm base. For heavily layered areas, use a heat gun or a chemical stripper. Paintwork that is in good condition just needs a thorough washing then a fine sanding. Spot prime any bare timber.
Blistering, flaking and peeling
Blistering shows up where dark colours have been applied over many layers of old paint or where moisture is trapped below. Eliminate the source of moisture, then strip back using a heat gun or chemical stripper. Seal cracks around windows and doors with a suitable filler.
Bare masonry, bricks and concrete
Allow new concrete surfaces to cure for a minimum of 28 days. Wipe salty or lime build-up away. Check all surfaces and remove loose material with a wire brush. If the surface is powdery, porous or highly glazed you will need to apply a primer recommended for the material - ask at your Guthrie Bowron store.
Scrape any areas of loose paint and feather the edges with a medium grade sandpaper. Use a suitable filler to fill any cracks or flaws. Spot prime, sand then wash the whole window frame down to remove the last dirt and grime.
Galvanised iron roofs, bare metal and spouting
Check your roof for soundness, and strip back old flaking layers of paint. Brush with a wire brush and spot prime any problem areas. Bare metal surfaces must be rust free and clean. Treat with a rust remover and wash down with clean water. Wash all metal or plastic spouting also.
Nail head stains
Replace old steel nails with galvanised nails. Sand or wire brush any stains off the paint then countersink the new nails to 3mm - 4mm below the surface. Spot prime with a rust guard product and then fill and sand.
Any bare timber which has been exposed to the weather for more than a month needs to be sanded back before painting. Rotten or decayed timber must be replaced. Where movement is possible - around doors and windows, apply an exterior flexible filler.
Step Two - Pre-paint coatings
You've spent valuable time preparing your surfaces, but you need to put on your first layers of cover, before you put on your final colour. Pre-paint coatings are essential if you want to achieve the best finish; without being sealed, primed or undercoated, your surfaces just will not look their best, or last as long.
As a general rule, bare timber must be primed. The type of undercoat varies, depending on the surface. If you're not sure which sealer, primer or undercoat to use, have a chat with the friendly staff at your local store, who'll be happy to help.
Not sure how much paint you'll need?
As a quick guide, 1 litre covers approximately 15 square metres.
Step Three – Applying the paint
For the final coats, choose the finish that best suits the material you're coating and the durability you need.
Pre-moisten your brush with the right liquid - water for acrylics, turps for oil based paints. To stop paint running down the brush handle, don't dip your brush more that 30mm into the paint can. Tap it to remove excess paint.
Gloss: Shiny, durable - ideal for doors and windows. Withstands harsher cleaning.
Satin: Also called semi-gloss or low sheen. A hard working easy clean surface, ideal for woodwork.
Surface-by-surface paint guide
Weatherboards: Gloss, or semi-gloss for long durability.
Woodwork: Enhance the natural timbers with a satin or semi-gloss finish.
Doors and windows: Gloss or semi-gloss enamel. Some acrylics are suitable, but ask our staff for more advice.
Galvanised iron roofs: Use a specialised water-based roof paint.
Fences: Low sheen water-based paint.
Painting in the right order
Work from the top down. Complete the roof, gutters, fascias and eaves, down to walls, doors, windows and baseboards. Paint weatherboards in two stages for fast easy painting. Paint the underside first, then the face.
Applicator paint pads are ideal for 'cutting in' around door edges.
Handling the paint
Thoroughly mixing your paint is vital. Make sure the temperature hasn't dropped below 10°C or the paint won't flow smoothly or set properly.
Check the guidelines on your cans for re-coating times. It's important to follow these suggestions, taking into account the temperature, humidity and the type of paint you're using. One heavier coat is not as good as two - it may not dry properly. Remember to never paint over an area that is partially dried. Leave runs and re-sand once dry.