Weatherboard rot repair - treat/prime/fill/prep?

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muncedog

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#248138 11-Mar-2019 22:24

Google leads to many approaches and marketing ploys so looking for answers from those with experience! I'm hoping the responses to this question can be a good reference for many people when repairing small defects to weatherboard (not large, I know to cut out etc). Just a few questions around the process:

1)Removing soft/rotten wood but how far to go - sand/chisel/cut what's too soft to keep, how far is too far and time to cut out and replace?

2)Soft/damaged wood hardeners to 'harden'/'stop rot' on any remaining wood - just a marketing ploy or good idea?

3)filler vs putty vs bog - linseed oil, acrylic (water?) vs polyester vs epoxy based? Marketing info states they all are wonderful for all jobs!

-something different for cracks vs holes vs larger gouges?

-Something that doesn't dry/shrink and fall out and can be painted?

-flexible to move with the wood, yet can put a nail through it?

-for unseen areas where painting/appearance not the priority which gives the best performance?

4)Primer/treatment - is it necessary if raw wood already covered with filler etc? for other patches e.g. chemical treatment that absorbs in or just a first layer of primer paint (or even just undercoat?)

Your thoughts/experience on 1-4 would be greatly appreciated!

Bung

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#2196168 11-Mar-2019 22:55

You probably could have kept this in your other thread. @neb was starting on wood rot using pva and a fungicide mix to stabilise the remnants of the rot. Maybe he has some results?

neb

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#2196180 11-Mar-2019 23:37

Bung: You probably could have kept this in your other thread. @neb was starting on wood rot using pva and a fungicide mix to stabilise the remnants of the rot. Maybe he has some results?

I won't know for some years :-). In brief, dremel to get the bulk of the rot out, wood stabiliser (fungicide + diluted crosslinking PVA) in several coats, and then builders bog, with flexible acrylic sealant in seams likely to flex a bit in weather. You can't tell it's been patched afterwards.

netspanner

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#2196273 12-Mar-2019 08:13

Find the next vertical or a few back just to be sure.

Use a skillsaw and cut it over the middle of the vertical. Cut the underlaping part of the board with a thin saw.

Remove all the nails with a crowbar - you can get really thin weatherboard specific ones with are awesome.

Use a hacksaw to cut the nails that are on the top weatherboard otherwise they will stop a new board sliding in. I cut them at the top and the bottom of the nail.

Paint the end of the new ones after cutting them and let it dry. I also paint any other exposed wood such as the ends of the remaining ones as well.

Put the new ones in, hold a level to make sure they are horizontal, you might not notice it when you hammer it down but you sure do when you step back.

Seal it with weatherboard filler - it allows moving of the boards that normal gap filler doesn't, then paint.

Just learned that from doing my own house.

muncedog

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#2196286 12-Mar-2019 08:31

Thanks all for the tips - starting to make more sense now :)

neb: I won't know for some years :-). In brief, dremel to get the bulk of the rot out, wood stabiliser (fungicide + diluted crosslinking PVA) in several coats, and then builders bog, with flexible acrylic sealant in seams likely to flex a bit in weather. You can't tell it's been patched afterwards.

Interesting to know a dremel is useful and the application of a treatment then effectively a sealer (presumably PVA mix forms a skin/seal) - for painted areas I presume a primer could be used in its place?

I envision builders bog is a general term, does anyone know the typical chemical makeup? It's best used for large repairs but what about the small/cracks etc?

Anyone had experience with polyester/epoxy/acrylic sealers or putty - just trying to get a feel for the differences!

neb

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#2196567 12-Mar-2019 15:04

muncedog:
Interesting to know a dremel is useful and the application of a treatment then effectively a sealer (presumably PVA mix forms a skin/seal) - for painted areas I presume a primer could be used in its place?

I used it with what's effectively a router bit, so something a bit like this, you can get them from China via eBay/Aliexpress, with the narrow neck of the rotary tool it was easy to get into tight corners and shred out the rotten fibres. Probably Trademe as well... yeah, like these.

The PVA wasn't a sealer but a hardener, so the crosslinking PVA/fungicide mix penetrates any remaining rot and wood and turns it into a hard plasticky substance, You can get commercial wood hardener that's either cross-linking PVA or resin-based, but it's several times the price for the same thing.

muncedog:
I envision builders bog is a general term, does anyone know the typical chemical makeup? It's best used for large repairs but what about the small/cracks etc?

It's the same as automotive bog, better for large repairs but has the advantage over most one-component fillers that it doesn't shrink on curing, is easy to work with when it's part-cured, you can shave it like cheese, or file/sand it once it's fully cured. Downside is its not flexible, which is why I did the alu window frame seams with acrylic sealer, then bogged over it, with the acrylic acting as a flexible buffer.

Can you post a photo of what you're trying to deal with? That would help in terms of providing feedback.

neb

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#2196569 12-Mar-2019 15:07

muncedog:
I envision builders bog is a general term, does anyone know the typical chemical makeup? It's best used for large repairs but what about the small/cracks etc?

Oh, if you're in Auckland I've got a small amount left that you have have to play with, see how it goes. Used nearly half a kilo of it to rebuild the window frames.

muncedog

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#2226275 27-Apr-2019 12:48

neb:

The PVA wasn't a sealer but a hardener, so the crosslinking PVA/fungicide mix penetrates any remaining rot and wood and turns it into a hard plasticky substance, You can get commercial wood hardener that's either cross-linking PVA or resin-based, but it's several times the price for the same thing.

.

Thanks for your help on this neb. I just have a couple of questions where recommendations would be greatly appreciated.

This fungicide/hardener combination I am using for areas where I am repairing (filling) rot.

For the corner sections however, I presume I don't necessarily need hardener as I'm no longer looking to fill/repair as the damaged area will be under a cover board. I have removed rot back to reasonably firm wood and only really need to treat (fungicide) and seal from moisture not UV. I am short for time so If I can do this in once step e.g. no top coat/sealing paint/pva/fungicide steps that would be awesome. Also, even if it costs a little bit more, that's OK as Id rather be reassured its holding up as it will be hidden under the corner board/near framing.

Given this situation, I am wondering if a single coat of a penetrating epoxy (advertised as hardener/sealer/fungicide) would be best - any experience with these as the final coat?

e.g. https://www.bunnings.co.nz/norski-epoxy-timber-sealer-1l_p00277212

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neb

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#2226341 27-Apr-2019 14:27

I don't know of a one-step solution, sorry, you're going to need at least two, one to seal the timber/rot and a second to patch, because they're doing completely different jobs. OTOH two-component anything usually sets pretty quickly, you could do the epoxy in the morning and bog and paint it in the afternoon, it's the moisture/air-cured stuff where you need to wait around for it to set. I would definitely paint it, sealing out environmental intrusions is a must for anything exposed to the elements.

muncedog

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#2226344 27-Apr-2019 14:37

neb: one to seal the timber/rot and a second to patch, because they're doing completely different jobs. OTOH two-component anything usually sets pretty quickly, you could do the epoxy in the morning and bog and paint it in the afternoon

Hi Neb, thanks for the fast reply & advice. I realise this is the case with the sections I am filling but note I am not looking to fill/bog for this part as new wood (coverboard corner box) is going over the top!

I'm just looking to stop/seal from future moisture damage! Hence why I was wondering if an epoxy doesn't need sealing in this case - I notice they mention sealing for UV reasons but this is UV & rain sheltered!

Any thoguhts? Otherwise good point on fast setting components , thanks

neb

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#2226347 27-Apr-2019 14:45

I don't really know beyond guesswork, sorry. My instinct would be to seal/paint because the epoxy hardener was designed as a surface-prep mechanism that other stuff goes over the top of, but I guess it should be OK, epoxy is pretty durable and ingress-resistant.

muncedog

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#2226406 27-Apr-2019 15:46

Thanks! I'll update the thread when I finish! Cheers

pctek

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#2226466 27-Apr-2019 17:59

1)Removing soft/rotten wood but how far to go

All of it. If you don't it spreads.

2)Soft/damaged wood hardeners to 'harden'/'stop rot' on any remaining wood

Ploy.

3)filler vs putty vs bog

Builders bog. The stuff you mix, pink coloured.

But better to replace the wood if too major.

muncedog

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#2226477 27-Apr-2019 18:27

pctek:

1)Removing soft/rotten wood but how far to go

All of it. If you don't it spreads.

2)Soft/damaged wood hardeners to 'harden'/'stop rot' on any remaining wood

Ploy.

3)filler vs putty vs bog

Builders bog. The stuff you mix, pink coloured.

But better to replace the wood if too major.

Agreed to remove as much as practicable. For what remains I wasn't sure if single step epoxy hardener (advertised as hardener/sealer/fungicide) was possible as it will have UV/rain shelter from another timber board. E.g norski timber sealer or epg timber sealer
http://epoxyglue.com/timber-sealer.html

Otherwise better results might be obtained? with 2 step fungicide/penetration and then sealer (paint) and possibly even top coat. I realise this may only slow down the rot, but that's ok. If a superior result is obtained this way that's ok but it will take much longer and not be set hard. That's essentially my question!

I took a look today at a couple of products - norski timber sealer and resene timberlock.
Lastly epg timber sealer - another 2 part epoxy at reasonable cost.

Also got myself some 2 part bog for other areas. This area doesn't need filling!