House Painting - Undercoat or not?

[Pavo]

Hi Guys,

I know this should be on a home improvements site, but I don't know of or visit any.

I will soon be re-painting my weatherboard house where I will be stripping back all the old paint to bare timber and re-painting.

I know that Dulux Weathershield and Wattyl Solarguard can be painted on without priming, but is it better to prime? If so, oil or water-based?

I emailed Dulux and asked the same question and they said given the age of the timber weatherboards (50 years old) they said to use their oil based one step.

So my options are:
1. 2 coats of Dulux Weathershield direct on the timber
2. 1 coat of water based 1 Step Primer Sealer Undercoat, 2 coats of Weathershield.
3. 1 coat of oil based 1 Step Primer Sealer Undercoat, 2 coats of Weathershield.

What do people think? (I know Dulux has already offered me their advice, but just thought I'd confirm it). Remember the hard part if the sanding/stripping, so one extra coat of sealer is no hassle in the scheme of things if it is considered worthwhile.

Any help is much appreciated.

Thanks,
Pete

[V8Ian]

Obviously the more coverage the better, undercoats are cheaper than topcoats.

[big guy]

I am a builder and I follow the spec sheets for any specific paint.
Don't just ask a painter, ask the manufacturer.

For bare timber, it will need a base or sealer, no doubt, the one coat does all is for handy men/woman.

In painting, its the amount of coats and the right coats.

3 thin coats will give much better results than 2 thick coats..
Same goes for cars, just more coats.
For exterior, also a Acrylic is best, it lasts longer and does not go dull.

Good paint is expensive, its worth it though.

the finish is also directly proportional to the prep work.
Take your time and it will show in the result.

Enjoy:p

[Mudnut]

If it is old bare timber, I would use an undercoat, which will soak into the timber somewhat, and be cheaper than the top coat. Just a trade secret, have the undercoat tinted to the top coat colour. This will help with the coverage of the top coats (should be 2). You also get a chance to see your colour on the house, and can make adjustments to it if you don't like it.

Just painted a weatherboard 2 story house ;)

Ken

[jerryd]

I've used Wattyl Solarguard Gloss on timber fascias and gable boards, even though they say no undercoat needed I used two coats of acrylic primer first, followed by two top coats. You'll definately get a better finish and it should last a bit longer too. Like big guy says, more prep and coats will give a better result. Hope this helps ;)

[amtravic1]

I am a builder as well, and the advice from Dulux sounds ok, Oh and stuff painting, employ a painter, it has to be the worst job around, rather be digging holes in 40c heat!

[Pavo]

Thanks everyone.

I will use an undercoat and go with Dulux's recommendation of an oil based one.

As for hiring a painter - nah, I do this kind of stuff with my dad. I've painted plenty before. But the preparation is going to be a lot of work!

Once again, thanks - it's good to have the advice confirmed.

Pete

[hiline]

I am a builder as well, and the advice from Dulux sounds ok, Oh and stuff painting, employ a painter, it has to be the worst job around, rather be digging holes in 40c heat!

closely followed by concreting :D;)

[rockyroad]

Good advice. Agree with everything said except that platering would be the worst job.

[clive22]

The main problem I see with your spec is removing the old paint, this is really not necessary, only paint that is loose and no longer adhering needs to be removed. If it stays on the new coats will prevent it from further UV and water degradation.

If you can remove the existing paint with moderate effort with a scrapper then it should come off. You can also criss cross it with knife cuts at say 4mm apart and try to remove with good quality adhesive tape. Again if it comes off easily then strip otherwise leave.

Leave strippers, thermal guns well alone these are too strong - if you need the adhesive bond is ok. Reaplce weatherboards that are too rotten, otherwise rot treat.

Depending on the amount of existing paint film that needs to be removed you will end up with an uneven surface, about the paint thickness. Get a water based filler, e.g. timber mate and thin down with water until about like a cake mix consistency.

Paint, trowel on lightly using very flexible blade (not putty knife) this over the depressed regions until lightly overfilled. Then sand smooth and remove any gloss from the existing remaining paint (say 180 grit paper), the new paint needs a 'tooth' to adhere to.

With priming use an oil based primer if the timber may bleed, dark timber e.g. WRC, merbau (unlikely for W/B) are the worst for this. Baltic pine is a very common timber for W/B and the self priming acrylics paints Solaguard, etc. no priming is required over non bleeding timbers. Oil based primer is required if they may bleed, this is mainly an issue with new timber.

Depending on how well the wall comes up would generally hedge towards low sheen finish as it hides surface imperfections more, and gloss paint tdrops its gloss anyway in a couple of years under the sun.

I hope you can trust me about not removing the old paint as it really is unnecessary and will save you so much work. Make sure you get a good respirator old paint can be very nasty.

I am a qualified among others a NACE coating inspector and have worked in around coatings for a long time.



Clive

[El Duderino]

Hi Guys,

I know this should be on a home improvements site, but I don't know of or visit any.

I will soon be re-painting my weatherboard house where I will be stripping back all the old paint to bare timber and re-painting.

I know that Dulux Weathershield and Wattyl Solarguard can be painted on without priming, but is it better to prime? If so, oil or water-based?

I emailed Dulux and asked the same question and they said given the age of the timber weatherboards (50 years old) they said to use their oil based one step.

So my options are:
1. 2 coats of Dulux Weathershield direct on the timber
2. 1 coat of water based 1 Step Primer Sealer Undercoat, 2 coats of Weathershield.
3. 1 coat of oil based 1 Step Primer Sealer Undercoat, 2 coats of Weathershield.

What do people think? (I know Dulux has already offered me their advice, but just thought I'd confirm it). Remember the hard part if the sanding/stripping, so one extra coat of sealer is no hassle in the scheme of things if it is considered worthwhile.

Any help is much appreciated.

Thanks,
Pete

I've recently repainted my whole house, which is a weatherboard...have fun! :wasntme:

I stripped the boards right back and did countless hours of mind-numbing prep-work. A lot of paint companies these days claim they don't require priming before painting, but I decided to put a coat of oil-based primer down regardless. Too much time was spent doing prep-work, so it seemed good insurance anyway! It also made painting nice and easy.

In total, I put 1 coat of quality primer, and 3 coats of weathershield expterior paint. Put in the time n effort doing the prep-work properly n don't rush it or take shortcuts. The finished result has been excellent and it looks brand new!

[Pavo]

Clive22,

Thanks very much for that - a lot of good advice. I am very willing to believe you about not removing all the paint. My main problem is that I think the house was painted 7 years ago (or so) just before I bought it - and there are a few blisters/cracking sections in the paint now. The blisters seem to go back to bare timber (which says to me that the very first paint job is the failing one, not the newest). I am concerned that even if I fix the problem areas now, will it continue to fail over the years?

You did touch on this when you said that the new coats will prevent further UV and Water degradation. So it's good to get some re-assurance there too.

Really, the house is still in very good condition and it's not like there are a lot of problem areas. There are no rotten weatherboards, so no dramas here (possibly some small sections).

I think the boards are a pine variety - I would have guessed Cypress, but could be Baltic pine.

So based on your advice, my plan will be:
1. Sand with 180 grit - all existing paint.
2. Repair all the blistered/flaking/cracked sections.
3. Use acrylic primer/sealer/undercoat on the repaired sections only.
4. 2 Coats of Solarguard or Weathershield. (Use Low Sheen - which was my original plan).

Thanks very much - very good and re-assuring advice.
Pete

[Pavo]

I've recently repainted my whole house, which is a weatherboard...have fun! :wasntme:

I stripped the boards right back and did countless hours of mind-numbing prep-work. A lot of paint companies these days claim they don't require priming before painting, but I decided to put a coat of oil-based primer down regardless. Too much time was spent doing prep-work, so it seemed good insurance anyway! It also made painting nice and easy.

In total, I put 1 coat of quality primer, and 3 coats of weathershield expterior paint. Put in the time n effort doing the prep-work properly n don't rush it or take shortcuts. The finished result has been excellent and it looks brand new!

Well this pretty much summarises what I was planning on doing...except only 2 coats of Weathershield. It's good to hear you had really good results from it. But clive22's post was also re-assuring about not having to remove all the old paint. I'll have a really good look at the quality of the current paint.

2 years ago I did major renovations and I had to save some of the original weatherboards - I did strip those back to bare timber before painting...like you said, it was fun!:)

Pete

[newhue]

Pavo,
I colour in houses for a living and have done so for 20 years. I did option two on my weatherboard house. Acrylic primer and two weathershield coats.
If you prime with dulux first coat, buy the buff coloured one opposed to white, it holds back any tannin staining coming through from the timber.
The tannin stain will only be an issue anyway if you paint your house white or any really light colours.
Honestly, acrylic primer is a whole lot easier than oil based. It fills better, doesn't stink, goes on easier, is better for the world, and does the job just fine. Acrylics have come a long way in the past 20 years.

Apply all coats as if you are not paying for it, don't be scabby, and you'll be a happy man.

Oh you can also use Sellies Rapid Filler for any filling you wish do. It's designed to be skimmed over the surface, not for nail holes or big hole filling. Timber mate is also OK as suggested by clive.

[El Duderino]

Well this pretty much summarises what I was planning on doing...except only 2 coats of Weathershield. It's good to hear you had really good results from it. But clive22's post was also re-assuring about not having to remove all the old paint. I'll have a really good look at the quality of the current paint.

2 years ago I did major renovations and I had to save some of the original weatherboards - I did strip those back to bare timber before painting...like you said, it was fun!:)

Pete

I guess every house has its own issues, so what you chose is entirely your call. My house is my grandparents old 1950's weatherboard place which was left to me. It had a bazillion layers of paint, some areas were looking a bit shoddy after years of being exposed to the elements, and some were pretty fine from being sheltered from the elements. For consistency and a bit of ocd on my part, I got the heatgun out, stripped the lot back to bare boards and went from scratch. To go over what was there in my case wasn't worth it, n was smarter to start over.

I put a 3rd coat of weathershield on because I had the paint left over, and didn't fancy returning to the job any time soon...overkill insurance for laziness. :p

I'll warn you now that this is defo the hard, tedious and time consuming way, but I don't regret it for a second mate. Like you said, you've had experience going down this path and understand the pitfalls and benefits, so weigh it up to your particular situation.

If you do decide to go bare-boards option for the whole house, invest in a Bosch orbital and a delta sander (I can't kill either of mine), and put some good tunes on your ipod..,couple that with an entry-level set of Sennheiser over-ear headphones ($50) n you'll be grooving away and uber-productive at the same time! Hahaha!

[slug_burner]

Hit the old paint with a pressure washer, if that doesn't move it then the paint is adhering fairly well and not much risk of letting go if painted over.

[El Duderino]

Hit the old paint with a pressure washer, if that doesn't move it then the paint is adhering fairly well and not much risk of letting go if painted over.

Please tell me that isn't your technique...we've been on stage 4 for years cos of the drought, unlike Melbourne! :p

[abaddonxi]

Hit the old paint with a pressure washer, if that doesn't move it then the paint is adhering fairly well and not much risk of letting go if painted over.

Unless your weatherboards are something really soft, like cedar, and then you'll be carving your initials in them.

[slug_burner]

Unless your weatherboards are something really soft, like cedar, and then you'll be carving your initials in them.

Yes.

And if you use a gas flame and hold it in one spot for too long the wood will catch fire.

Anything that does the job quickly usually has consequences if not used appropriately due to the power delivered. A bit like big motor bikes.

[El Duderino]

Yes.

And if you use a gas flame and hold it in one spot for too long the wood will catch fire.

Anything that does the job quickly usually has consequences if not used appropriately due to the power delivered. A bit like big motor bikes.

That's where technique comes into play...heat up the area while scraping. Never once had an issue with it, on my house or my dads. Buy a cheap heat-gun with a single setting and expect that scenario to unfold...buy a good quality one with adjustable settings n there's no issue. I don't use gas heat-guns...only electric. A bad tradesman blames his tools, but a good tool will dictate the finish. ;)

To use a bike analogy as well, big motor is fast in a straight line, but less power and better handling = cornering speed, which makes up the deficit and shows up the go-fast boys with technique and finesse. ;)

[slug_burner]

That's where technique comes into play...heat up the area while scraping. Never once had an issue with it, on my house or my dads. Buy a cheap heat-gun with a single setting and expect that scenario to unfold...buy a good quality one with adjustable settings n there's no issue. I don't use gas heat-guns...only electric. A bad tradesman blames his tools, but a good tool will dictate the finish. ;)

To use a bike analogy as well, big motor is fast in a straight line, but less power and better handling = cornering speed, which makes up the deficit and shows up the go-fast boys with technique and finesse. ;)

we are in violent agreement:cool:

[El Duderino]

we are in violent agreement:cool:

I like the cut of your suit Simpson. Bahahahahaha! :cool:

What do you ride btw???

[Pavo]

El duderino - thanks for your advice.

I think I will do it on a case-by-case basis. The western walls might need more love and care, while the more protected ones are probably ok to sand back slightly, seal, and paint.

Newhue - also thanks. I will use the acrylic undercoat - for all those reasons you mention. I hate oil based paint and would only use it if I really had to. Really I will do a quality job and I'm not sure if using an oil based undercoat will give me any noticeable difference in finish or life expectancy.

Pete