Resin for replacing rotten wood

[Jimk]

Styrene monomer

[Tim Watts]

Hi,

Sadly I've had a condensation problem in the corner of a bay window that wen't un noticed for a good while.

Most of the frame is solid, but the core right at the corner has a rotten section. Inside surface is solid (apart from the top where the condensation was). Outside seems OK. I'd estimate perhaps a couple of inches in the middle has gone bad as I can push a skewer right through.

Will be a right pain to try to replace as basically we've have to cut out most of the corner which will probably mean taking the ali famees out after deglazing.

Frames are mahogany.

It's a bay holding up its own bit of flat leaded roof, about 2ft out from the house. Aluminium window frames. The corner section is pretty thick, a good 4x4" so plenty to spare.

I was wondering, in the summer when it's been dried out, whether to fill it with a thin epoxy that will soak into the weakened wood and then go on to fill any remaining void. The load is purely compressive so it doesn't seem a totally bad idea.

Any recommendations for epoxy or resin and possible filler (sawdust, silica, something else?)

Something fairly thin that will soak in, but also able to set in bulk mass.

Cheers,

Tim

[GB]

Wood hardener is what you want. Then fill the hole with car body filler.

If you want it done by a specialist, you could ask your dentist to do it?

[John Rumm]

Is the painted or a real wood finish?

In either case, chop out[2] what bad bits you can. Then use wood hardener on the bits you can't really get at. If its a natural wood finish then scarf in new wood where possible, and use a good with a two part wood filler like Ronseal's[1] to make good. If painted, then you can be more liberal with the filler.

[1] Worth going for the branded option IME - many of the competing products mix and set well, but are then complete bastards to sand after. [2] Multimaster type tools come into their own here.

[Andy Burns]

One of the ends of the cill on my lounge window rotted away, I cut it out, applied plenty of this hardener which soaks in.

chopped-in a block of wood to fill most of the hole and built up the gaps with body-filler, sanded and repainted ... that repair was the most solid section of the cill about 20 years later when I replaced the window.

[Brian Gaff (Sofa 2)]

If its really Mahogany, I'm very surprised, that is bloody hard wood, I used to make things of it at school, after many years in a damp garage, it was still as good as new. Brian

[Brian Gaff (Sofa 2)]

Is that what we used to call Plastic Wood? Pretty good stuff that but I did used to find if it was a place where temperatures varied a lot that it eventually fell to bits. Brian

[Tim Watts]

Hi John, and also replying to Andy and GB for brevity:

Thanks for your respective replies.

On 05/01/2020 23:46, John Rumm wrote: > Is the painted or a real wood finish?

Varnished inside and microporous sadolin on the outside.

This is the inside:

(Google Drive, no signin necessary)

Most of the damage is under the trim so I can either replace or splice in a bit of trim made to the same profile.

"Worst" is where a skewer goes down and right through to the bottom, and I suspect the mush extends under the upright.

To be fair, some of the damage may have been legacy from external water ingress:

That I fixed a few years ago - all the joints were open and some rot, so I spliced in a block of sapele (original frames looked like mahogany) and sealed up the joints with The Works and painted with one of the sadolin products - which could do with a recoat now.

Thanks for the vote of confidence in wood hardener. I think there's nothing to be done until summer when (it's a south facing aspect) the sun bakes all the damp out of the frames.

I'll dig down from inside with a multi tool and aim to saturate the whole area with hardener then fill it up with 2 part filler.

If there's any question of the whole corner being too far gone, I think I could replace the original patch with a full section deep splice that goes right to the cill that would ensure the corner post is fully supported:

There would be rot to the left of that under the frame, but it would not be affecting the structural support of the flat roof above.

OK - I guess we have a plan A and a maybe Plan B if required that don't involve taking the metal frames out.

====

On an aside, part of the problem is that the DG is old, blown and the dessicant is waterlogged so there's more thermal bridging which isn't helping the condensation.

I'm repacing the affected DG panels in a couple of weeks with low-e units so that may help.

The problem was that I had foolishly hung net curtains inside the main curtains for privacy and that was clearly trapping humid air (it's a bedroom). With those gone, it is starting to dry out.

Cheers :)

Tim

[Andy Burns]

It's not a two-part filler like body filler, but for colour matching you could buy a dark shade and a lighter shade of this, the actual colours in the tin vary pretty wildly from the supposed colour swatches, but they mix well ...

[Andy Burns]

Though last year, I found none of the sheds sells all the colours, so expect to do a SF/TS/B&Q tour to buy the right combination ...

[Tim Watts]

On 06/01/2020 08:59, Andy Burns wrote:> Tim Watts wrote: >

Ah - I see.

I'll bulk fill with some 2 part stuff so it adds a bit of solidity back, but I could finish the top 1/8" with this stuff.

Thanks for the link :)

Cheers,

Tim

[Chris Green]

Although mahogany is a 'hardwood' in the sense that it's from a deciduous tree (I think) it isn't actually *very* hard as hardwoods go.

[Tim Watts]

On 06/01/2020 10:14, Chris Green wrote:> "Brian Gaff \(Sofa 2\)" [e-mail]> wrote: >> If its really Mahogany, I'm very surprised, that is bloody hard wood, I used >> to make things of it at school, after many years in a damp garage, it was >> still as good as new. >

It's not that hard as you say - but it does quite well in the wet. By all rights the entire frame everywhere should be mush given how little varnish was on the outside when I took the house over. And they date to the 70s or early 80s.

[The Natural Philosopher]

Just scraoe out anything that is totally loose, and then go to halfords

You can get polyester resin in liquid form and that wull stabilise anu porous stuff, and then simply fill the rest up with car body filler - which is poluester resin with a filler in it. THis is sndable and paintable and works brilliantly.

If you want it to look like wood, well that is not so easy. Suggest buyng mahogany sheet and letting it into the surface

[Robert]

U-Pol fantastic has been used on my wooden sash windows, maybe because of contacts with the local car body repair shop ! Result has been very good.

[ss]

I had 2 external corners with rot in them. Scraped out all the loose stuff then used a wood hardener. once dried I then filled with 2 part epoxy, sanded then painted. Been good for last 6 years and still solid.

P.S. for sanding epoxy try and catch it just before fully hardened as it is then much easier to sand.

[alan_m]

You need a wood hardener such as Ronseal Wet Rot Wood Hardener

It has the consistency of water and will soak into soft wood and then harden within an hour. Perhaps drill a hole in the wet wood and use a syringe to get the hardener to the core of the damage. Google or Ebay search for "ink syringes" - many available and sold for refilling ink cartridges.

Use a two part filler to fill the hole - a car body filler or a similar two part wood filler whichever is easier or cheaper to obtain.

[GB]

The two part wood filler that John recommended may be better?

[newshound]

No. Modern wood hardener is some sort of polymer dissolved in solvent, this soaks into the porous rotten material and then sets. It is pretty effective (but not particularly cheap).

[Tricky Dicky]

I have used the Ronseal hardener and their filler to fix some rotted window sections and found the hardener most effective if as much of the soft stuff is removed if I recall Ronal recommend for deep rot to drill holes into it the wood past the extent of the rot and fill up the holes with the liquid hardener this will then soak in and give deeper penetration.

Richard