House painting

Ooh, boy.

Preparing weatherboards

Assumptions. Timber weatherboards. Hardies, asbestos, flatboard, monolithic, brick etc. are all different.

Non flakey paint. If it isn't flakey, it isn't worth the effort of stripping. Just give it a good sand with ~120 grit sandpaper to "key" the paint. Exterior paint tends towards the glossy end of things (full gloss, semi gloss, in some cases satin but that is usually for monolithic coatings). You don't want to take the paint off or make it change colour, you're only aiming to make it relatively dull/matt so the next coat (see below) adheres as well as possible.

Method. I usually do this by hand with a cork sanding block. Depending on the profile of your weatherboards, you may be able to use a random orbital sander. I would not use a belt sander. Unless you know what you are doing, they are too aggressive and over long runs (like horizontal weatherboards) you can get "waves" if you take more off in some places than others. It's not obvious if you look at it directly, but much more obvious when you look along it.

Flakey paint. If the paint is in any way flakey, you will need to strip back to something sound. That is often bare timber, sometimes a decent base coat.

Method. I use a linbide scraper. You can get different profiles (flat, rounded, corners). If you get the knack, this will rip through flakey paint really quickly; for long stretches, I hold it out the back of my hand and use a sort of scything motion. Stubborn bits I use a heat gun to soften. But if anything is really stubborn, you probably don't need to strip, just key like above. You will need to sand a bit more aggressively at any hard edges of stripped --> painted to feather out the edge so it doesn't have a line when top coated.

Lead. Watch out for lead paint. Looking at the back of a flake, the most common indicated is it is usually dark red. You can buy testing kits or can get these tested at paint shops. Last I heard (though this was a while ago) if lead is found, you have to scrape (not sand) into plastic drop cloths to collect the flakes and dispose at your tip. It is obviously far from ideal and you should not be eating it (apparently it tastes very sweet), but if it is large flakes it is not insta-lethal.

Rusty nails

Recommendation. Especially if they are at the top of scaffolding, don't faff about with treatment. Get a sharp dog bar and some nips and remove the nail. You will probably make a mess of the weatherboard, but it is far easier to bog a hole than effectively treat weatherboard rusty nails (especially if it is a larger nail). Replace with a new stainless steel nail of slightly greater diameter. Bog/fill. Sand. Paint. Done forever.

Rust is water soluble. Exterior paint is water soluble. Any significant amount of rust will find a way through, no matter what you do to prevent it. And then you will be re-hiring scaffold and doing this anyway in a few years.

Ignored recommendation. Sand all rust from both paint and nail. Treat with oxalic acid (e.g., CRC rust treatment). Counterpunch nail. Re-treat with oxalic acid. Fill hole with oil based filler (e.g., linseed putty). Wait recommended drying time (for linseed putty, ~2 weeks). **Spot** prime only with oil based primer. Wait recommend drying time (usually next day). Apply oil based undercoat. Wait recommended drying time (usually next day). Apply acrylic undercoat. Dry time etc. (2 hours). Then start painting your weatherboards. Odds are, this won't work (especially for large rusty nails) but this will give you the best chance.

Filling

Nail holes. Favourite: PAL contract filler. Easier to use, almost as good as Permafil. Second favourite: Permafil. I feel like this produces slightly better results, but is harder to use.

Bigger holes. Ados Builders Fill.

Technique. Generally counterpunch nails / countersink screws. Spot prime hole. Fill. I've come around to using plastic spatulas/scrapers for this. Let dry. Gently scrape with linbide scraper. Sand. Prime. Paint.

Gaps. Absolute dogs b0ll0cocks is Selleys Paint Over. Incredible finish, so easy to use. But expen$ive! I only use this in presentation areas, e.g., around front door. Generally use No More Gaps Exterior. Also good, not as good as Paint Over.

Technique. Cut caulking nozzle to shallow angle. Mark top dead centre (for me, black) and top dead bottom (red). Apply by "pulling" the bead with the point at the back. The marks help keep the point where it should be for a neat finish. Keep bucket of warm water nearby with non-linty rags. Use a wet silicon finger/finisher to lay off, then tidy up with wet clean rag. After a bit, toss into bucket. Have 3 or 4 rags on the go. By the time you've used up a rag, the first one will be clean (enough) to reuse.

Soakers

I use vertical soakers over weather board joins. Use stainless steel with stainless nails. They can be harder to find than galvanized but as above, it isn't worth faffing about. You will probably need to use a chisel or bar gently to prize up the weatherboard above and slide in. I put a vertical bead of no more gaps on the back before inserting to seal as much as possible, but don't seal the bottom, you want to plan for things to leak and have a way for the water to escape. So in practice: pry --> dry fit --> mark location with pencil lines --> remove --> goo the back --> reinsert --> remove prying implement --> nail

I personally don't like the corner soakers. I find they tend to seal problems in. I always do corner boards now, but that is a lot more difficult if you don't have experience or someone to ask for help. If you are using corner soakers, I would suggest using a timber preservative (e.g. timberlock) before priming to make the corners as hardy as possible.

Painting

Compared to the prep work, this is kind of the easy bit. Don't cut corners here, or you will regret it when you are re-prepping in 5 years instead of 10 or 15.

Washing. Wash before you paint. You will need to get all sanding dust, dirt, salt, mould etc. off. I live coastal and wash every day I'm painting to make sure there is no salt. If you're somewhere less harsh and windy, you might not need to wash daily. Use bleach/mould killer on any mouldy bits (often the south facing side).

Priming. Bare timber needs to be *primed*. Use a *primer* (porous material - e.g., concrete, gib needs to be *sealed*. Use a *sealer* for that). Unless you are painting cedar (or rusty nails), you will almost certainly want an acrylic (i.e., water borne) primer. I use Resene Quickdry which is an "acrylic primer undercoat". I forget the name of the Dulux equivalent but there is one. Most native timbers need an acrylic primer (oil will not penetrate properly), but it is far more UV resistant than oil based and so will survive the harsh NZ UV much better.

Ideally you should also spot prime nail holes and filled areas.

Undercoating. Resene Quickdry is an acrylic primer undercoat. I think the recommendation is 1-2 coats, i.e., one coat can be both a primer and an undercoat but for the NZ environment, I always do one of each.

In practice: use the same bucket of APU. Spot prime bare timber. Then paint the whole thing once. i.e., bare timber gets two coats, already painted timber gets one coat.

Top coating. Two top coats of your choice of colour. Typically this will be either full gloss (e.g. Resene Hi-Glo) or semi gloss (e.g. Resene Sonyx). I have recently used Resene "Cool Colour" range. Seems to work but have not done AB testing on normal vs cool colours

Technique. Buy smaller buckets with handles that can hold brushes of different sizes (e.g. https://www.bunnings.co.nz/paint-partner-700ml-paint-pot_p0328952). Use a cutting in brush (I use this style, 38 mm though some prefer the longer "rat tails" and a 25 mm will be useful in places) to cut in and top and bottom of the weatherboard. Then follow (or have a second person follow) with a larger 75/100 mm brush to complete. Try and "paint with a wet edge" i.e., wet paint going over wet paint. If it is semi dry it will "lag", sort of pull and tearing the surface. Leave it to dry completely and come back. Especially if it is warm, do the whole run of weatherboard then the next one - like a dot matrix printer. If the weather is warm, it will probably dry too quickly if you try and do multiple boards at once. Sometimes not always practical. And obviously you can stop at natural breaks (e.g., windows).

Other tips. Plan your day. Try never to paint in direct sunlight. e.g., paint the west face in the morning, east in the evening. This isn't always possible. Don't paint in the rain or if dew is going to come down before it dries. If you're flipping between brushes, cover the one you're not using with a clean damp rag. Between coats, you can wrap wet brushes in plastic and stick them in the fridge but it makes a mess. I just make the effort to clean properly between coats (an old scrubbing brush is good for this).

Final steps. Collapse. Make all sorts of promises never to do this again. Wait 10-15 years. Get extremely large quote to have house painted professionally. Start to think "It wasn't *that* bad last time..."

Sources/disclaimers: As a student job many years ago, I worked in a Resene paint shop. I tend to default to Resene due to familiarity but in fairness, Dulux is also excellent. Everything else is things I learned the hard way.

elpenguino

mdf