First though, have you checked that your paint doesn't contain lead? If it does, get the right advice on removal and disposal of the paint.
There is always the decision to be made when repainting your home -- do you strip all the paint off back to the bare timber or are the paint and weatherboards sound enough to clean, sand and spot prime? For sound weatherboards you may be required to:
Scrub your weatherboards with a good roof and paint cleaner to remove dirt and grime. Wash all chemical residues off -- water blasting can be used to remove dirt, grime and flaking paint, but care must be taken as it can be easy to be over-enthusiastic and blast the paint right off, damaging the timber permanently by stripping the surface layers off.
Moss and mould can be dealt with by using a good moss and mould killer. Thoroughly wash or water blast the surface after to remove all residue of the chemical.
Chalking is just that. Rub your hand over the weatherboards and you end up with chalked paint on your hands. It is caused by the breakdown of the paint surface by sun and moisture over time. A good roof and paint cleaner will deal with this problem.
With flaking paint and cracked paint, you need to ascertain why the paint is flaking. It could be that the wrong primer was used, causing the paint not to adhere. All flaking, cracked or loose paint should be scraped or sanded back, feathering the edges and spot primed.
Rusty nails should be removed where possible and, if not possible, punch the nail, prime, then fill and spot prime with oil based primer. Oil based primer will help stop the leaching of the rust stain.
Sand all painted surfaces to get a good key for the new paint to adhere to.
All bare timber should be spot primed with an acrylic primer undercoat with stained areas sealed with an oil based primer.
Remember to always paint on clean, dry surfaces that have a good key, and when priming native timbers use a water-based primer. We used an oil-based primer years ago on our window sills and had to remove the paint because it wouldn't dry. All part of the learning curve when it is your first renovation and very green at what you are doing.
Preparation for interior timbers is no different with the exception of not using a water blaster. Hot air guns and paint stripper can be used to remove paint and the rest can be sanded back then primer, undercoat and top coat, depending on the paint system you are using.
Some paints are self-priming, but you need to check with your paint professional as to what is the best paint to use for your particular job.
And on that note, happy preparation -- make sure it is a good one so that you get a great end result.
*Terry Lobb is an interior/kitchen designer and personal colour and style consultant who takes a holistic approach to living with colour, texture and style - email: terry@terrylobb.com.
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