Repair to fence posts

[Scott]

My friend has a wooden fence with wooden posts about 10 cm x 10 cm. It is not in great condition but she does not want to replace it as it is a mutual fence for nine flats and the others seem unwilling to contribute. We have secured any loose slats using screws (instead of nails) and painted it using Ronseal.

However, the tops of most of the posts have either rotted inside or been eaten into by the birds. Also, they are not level. I suggested levelling them and fitting galvanised steel caps but my friend does not want to incur this cost. She suggested pouring in cement. I think concrete would be better. Wood filler would be too expensive unless bought in bulk. One Strike would be expensive and I suspect unsuited to outdoor use. I wondered about squares of plywood but my friend thinks the birds would eat them too.

Any ideas for a low budget repair to some rotting fence posts?

[Brian]

They’ve rotted. The birds may peck at them but the rot is the problem.

Cutting corners won’t save money in the long run. Any porous filling/ cap will simply delay the inevitable.

You could make caps from plastic milk bottles, if you aren’t fussed about appearances. I noticed some like these on a walk. I looked liked they’d just cut a few inches from a milk container ( 4 l I suspect) and fixed it upside down on the end of the fence posts with a few roofing nails.

[Andrew]

The freeholder or management company should be making this decision.

Level ?. Do you mean no longer vertical, so not in line ? Could this be because they are rotting away at ground level ?.

Don't fill the indents with anything solid because you will accelerate the problem. Buying a 5 litre can of Barratime solvent- based wood preservative is one option. Just wait for a dry period and fill the indent with this and allow it to soak into the end grain.

Before VOC2010 it was possible to buy solvent-based end-grain sealer which would also have protected the tops but it all seems to be water-based now and useless for older damaged or previously treated timber.

You can buy proper wooden fence caps for 4 inch posts, but if there a significant indentation at the top of the post caused by end-grain water penetration then attaching caps might be tricky.

If they had been fitted with caps from new, then this problem would not have occurred.

caps made of lead or zinc would keep the water out and slow down the inevitable point where complete replacement is needed but such material is vulnerable to theft.

[Scott]

This is Scotland, where support of a majority of owners is needed. It is clear this support is not forthcoming.

For some reason they have been cut at an angle (maybe to try to prevent water ingress).

This will still leave a great big hole which seems to attract he birds.

My friend is disinclined to pay for caps on her own and is looking for a cheap fix. What about squares of plywood? I suppose this might be unsuitable outside.

[Andrew]

Get a square of fine-mesh galvanised metal support from a garden supplier. My local Mole farmers outlet sells a variety of mesh sizes in sheets about 2x4 feet intended for plant support or making rabbit hutches etc.

Cut these into pieces about 8 inches square and fit over the fence tops, then bend down the overlapping edges, remove small piece from each corner where is bends down and used the cut ends to make a secure rim.

[John Rumm]

WBP ply is fine outside...

Is there enough spare height to cut the posts off square at the top (to make a conventional cap work better, and get rid of some of the rot?)

Any spare bit of tannalised timber can be made into a cap if you saw some bevels on to the edges. I needed some small caps for 2x2 post, so just chopped down an ofcut of larger fence post:

[Animal]

No, it is not. I found that out the hard way. WBP is no longer a legally valid descriptor, if you see 'WBP' ply it's often in no way water tolerant.

OSB3 is water tolerant. (1&2 arent)

Chemical to stop rot & a cover might work for a while. Maybe. But if it's that bad its life is limited.

[John Rumm]

Then it wasn't actually Weather and Boil Proof (EN636, Class 3) then was it! (even if it was mislabelled as such)

Indeed, although it will swell a bit in thickness if left saturated IME.

[Andrew]

WBP? was used as security hoarding round a new house development near me a few years ago. They gave it a coat or two of blue oil-based paint and used uPVC fascia boarding along the top with the short edge over the top of the hoarding. When it was all removed it was obvious that the plywood was completely delaminating.

OSB3 edges will swell unless they are treated with end-grain sealant. If you then expect to line up boards that have been exposed to a variable amount of 'rain' then you will end up with 'steps' where there is a join.

Years ago the stack of OSB could be spotted because all the edges were green, sealed by the manufacturer, but they don't seem to do it these days (and when I redecked my garage roof the only endgrain sealer I could find was water-based).

[Theo]

This stuff is 50-70% hydrocarbons according to the MSDS:

have a 500ml branded 'Jakcure' version)

Theo

[Andrew]

"Specially formulated oil/spirit based preserver to protect cuts, drill holes and notches in pressure treated timber and decking where untreated wood is exposed."

So pressure-treated wood only does the outer layer ?. I thought the timber went into a giant vaccuum vessel and the preservative sprayed in while there is a vaccuum drawing it deep into the timber.

The stuff I am thinking off was either green or brown and used to treat the exposed cut ends of rafters on roof structures that have exposed timber ends.

[Robin]

It goes deeper than [most] other treatments but I've never seen any producer claim it goes to the core of everything from a fence panel to a

250 x 250 mm post.

Also bear in mind that in English "where" can also mean "if".

[John Rumm]

That is so, but it only penetrates consistently to a certain depth. While certainly more than surface deep - by the time you are 10mm in you will be back to untreated wood in many places.

This was a bit of tanalised 50x50 KD kiln dried sawn timber:

You can see the CCA penetration is much better on the newer growth rings than the older ones. It managed to reach right to the centre at one spot, but less much less at others.

Most spirit based wood preservers will wick up end grain nicely. You can get special products for use on green timber though to slow down the rate of water loss and control checking.