How to finish rough sawn cedar weatherboards?

[PujDD]

Hi all,

I've bought a house that needs some work. The existing weatherboards are rough sawn cedar stained with a semi-transparent walnut like finish. On 3 sides they need a bit of TLC due to varying levels of mould/mildew. The 4th side, the boards are cupping and rotting beyond repair. They need a full replacement, which I am getting a licensed carpenter to do. 

I'd like to take the opportunity to clean and refinish the existing boards alongside the new boards to protect them for the next 4-5 years and to keep a fairly consistent look to the home's exterior. 

I'm overwhelmed by the choices between oil based, water based stain and paint. A lot of people I've spoken with swear by oil based stains being the longer lasting option as it "seeps into the boards", where others say the complete opposite and that modern water based stains can be penetrative as well. I'm not the biggest fan of the block paint finish, but I have had a solid block paint finish recommended to me also as the most sure-fire way to achieve a consistent finish that hides imperfections and inconsistencies in the wear levels. 

I'm also stuck on the prep work involved. The boards on the east and west side look in fairly good shape to hold up against a power wash, and the boards on the north side are being replaced with all new weatherboards so no stress there. The southern face is fairly weathered and I'm concerned about excessive splintering or other damage from a power wash. You can see evidence of an attempted power was from some time ago (the grey patches of the southern elevation)

I've had a few painters come through to provide quotes, and they couldn't be more different: 

1. Power Wash followed by oil based stain (cheapest) 

2. Power wash followed by solid block paint (35% more than Option 1) 

3. Oxygen Bleach followed by dark water based stain (60% more than Option 1) 

4. Full sand followed by water based stain (95% more than Option 1) 

I'd like to avoid the full sand as I Don't really have the budget for it, but push comes to shove I can make it work if none of the cheaper options are suitable. I guess that's why I'm looking to the brains trust for advice -

1. based on the pictures (particularly the south elevation), how risky do you think a power wash is?

2. Is oxygen bleach effective to prep the boards for stain instead?

3. Given the state of the southern face, is a block paint really the way to go or can I get away with a semi-translucent stain? 

Images attached for reference. 

Thanks for your help! 

[MitchellMc]

Hi @PujDD,

It would be my opinion that if you were looking to stain and oil the timber, then I would start by having it all sanded, especially the weathered sides. It appears that the boards are beyond maintenance levels of deterioration, and they need to be resurfaced. You could prep them with bleach, but that isn't going to address their raised fibres and splinters. If you don't have them sanded smooth, then you will need to keep an eye out and recoat them at regular intervals to ensure they don't start to decay.

By sanding all the walls, you'll end up with the most consistent finish, and I believe this is the best approach for the long term. Sanding now and sealing could prevent you from having to replace the other sections in the future. Powerwashing is a faster, less cost-intensive approach that will help blast off previous coatings. However, it will damage the timber further and cause more grain to raise. It's not an approach I would recommend, but I understand you are on a budget.

If the boards are sanded, you'll get away with a water-based stain. The penetrative qualities of the water-based stains are comparable to those of oil-based stains, though possibly not quite as good.

Let me mention @Dave-1, @DIYGnome  and @Nailbag to get their thoughts.

Please let me know if you have any questions.

Mitchell

[Dave-1]

Afternoon @PujDD 

Love timber cladding Even tho it comes with extra work I still think its worth it.

I agree with @MitchellMc  with sanding the boards back as the first step, Tho I think Id go with oiling them instead of painting with a seal. Bunnings has timber samples you can look at showing the difference between the oil and the sealing that might be worth a trip to have a squiz. It also show sthe differnt types of oil and their lasting effects. The darker the oil the longer it lasts was what was explained to me.

Id actually be tempted since you are on a budget to sand and oil yourself, at least the rear wall near the carport and see if its something you feel up to.  Id do one side of the door and then oil it, then do the other side. That way you keep as much brightness to the timber as it will start to fade once you sand it within a short period of time.

The water blasting idea isnt something id be keen to try especiually as you have mentioned the deteriorated timber. That water blast is hard (yeah I have stuck my hand in front of it 🐵

[PujDD]

Thanks both! 

@MitchellMc @Dave-1 so what I'm understanding is: 

A. Sanding is the safest route to a satisfactory and long lasting result. If sanding down, I can get away with a water based stain. 

B. A heavy Power wash risks further splintering and damage to the boards, particularly southern side. Probably best to go with a solid stain or paint here to cover over the splintering - is that right @MitchellMc ? 

C. Oxygen Bleach could work to prep the boards but won't resolve the small amount of raised fibres and splintering - will need to consider regular reapplication of finish to prevent long term damage.

Given my budget and time constraints, I'm looking at B or C as the path forward.

Do you think I can get away with a water based stain after the oxygen bleach - as if so, I'll probably do that to avoid the risk of furthering the damage from the power wash. If your informed opinion suggests a solid block coloured paint either way then I'd probably save the $$ and go with the power wash in the hope that the solid paint can lock down the expected raised fibres/splinters and generally hide imperfections. 

[Dave-1]

Afternoon @PujDD 

I just went away to find out what oxegen bleaching is, So cleaning the timber is pretty much what it does. If you ware worried about long term effort in maintaining the timber maybe the solid paint is the way to go. You will still need to repaint every 9-10 years tho I think (From memory of looking into weatherboard houses as I love that type of wall) One thing I do know, do the prep work first and it is a lot easier to maintain/repaint down the track.

Dave

[EricL]

Hello @PujDD 

Looking at your earlier photos, it seems that the most exposed section is the Southern side. Would it be possible for you to do the sanding and staining in sections? It appears that the Eastern and Western section are not as badly exposed seeing as they have a bit of cover on them. 

If you were to sand the Southern side first, I propose investing in a belt sander or an orbital sander. This will greatly reduce your sanding time and you'll be able to stain, seal or paint that much sooner. 

However, if you are pressed for time and planning on using a pressure washer, I recommend testing the surface of the Southern side to make sure none of the timber has softened/rotted at the centre or the edges. Should the pressure washer hit these soft sections large chunks of your wall could be severely damaged.

Applying stain or paint over a pressure washed timber surface will work but is not ideal. Using Oxygen Bleach is not a guarantee that it will totally prep the surface. Deeply imbedded stains or sealers will impede any stains or sealers you might be planning on applying. It will thereby produce a blotchy surface finish.

If you have any other questions we can help with, please let us know.      

Eric