Treatment for timber post

10 Apr 2016
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United Kingdom
hi. We have a pergola in back garden and the timber frames holding up the roofing is starting to decay at the base.

What can I do to treat this? Please see pic. Timber is 19cm width around each side.

Pretty poor at anything DIY so will appreciate any input.

Many thanks.


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It is too far gone for chemicals. Probably you could poke a screwdriver in one side and out the other. Cut it out and fit a new leg?

Timber which is buried in the ground is pretty certain to rot at about ground level, where the water content from the ground and the air content from above reach the optimum proportions for decay.

You could also take the weight off it, cut out the bottom section, and splice in a new piece, or sink a concrete spur and bolt the sound part of the post to it. However from your pic it looks like the post is surrounded by concrete, which will make it difficult to dig.

Stand back and take some wider pics please.
Thanks for the reply John. I've taken a little vid if helps:

A pic also attached. Please let me know if a closer one is needed.
Many thanks for your reply.



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It's really annoying that they've used such large and expensive timbers and positioned them so they would be sure to rot. It could have been done with steel sockets spaced off the ground. I see the ground is paved with slabs so you could at least lift them to work round the post.

I suppose you could build brick plinths and fill with concrete, with a socket for the cut-off end of the post, provided the other side is restrained to prevent any sideways force from the wind, or sink steel angles and bolt the post to them. It will be tricky because you will have to support the pergola on props while working. I would really be thinking about taking it down. Even that will need care because such big timbers will be really heavy, and dangerous if they fall.

Let's see if anyone else has a better idea.

I see from your later pic that there is a substantial beam, so it might be possible to jack up props under it while taking out or replacing one leg at a time. However if there is a join in the beam, it would need skill to keep it all together. The roof will be pushing the legs away from the house.
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Ahhhhh. hope I don't have to lose it, we've not long moved in. Thanks for your reply, I'll look into your suggestions... GOOGLE!!!

Ta again John
What is the material I have highlighted here ?.


That needs to be removed as it is trapping water and keeping the base of the post damp.

It might be that the deterioration is limited to the outer surface of the timber and the central cores of the post are still sound.

If that is the case and the posts are just standing on the concrete ( not sunk below the surface ) thenn rescue may be possible.

The important thing is to seal the end grain of the post and arrange for water to flow away from the post.

I would

1) remove that surround.

2) lift the post and slide a sheet of 4 mm thick lead pad under the post.
Cut the lead so that it extends for about an inch all round the post.

3) lower the post onto the lead

4) fold the sides of the lead up to make a cup around the post.
Fill the cup with a good timber preservative such as Sadolin Classic
Allow the preseravtive to soak into the timber for several days. topping up when necessary
Paint the post with several coats of Sadolin

5) trim the lead to be the same size as the base of the post

This is based on experience of building a post and beam timber framed house where the posts rested on lead pads.

post and lead.jpg

Built in 1980 the posts show no sign of significant deterioration after more than 35 years .
Many Thanks for your replies. Is there a way of testing how solid the wood is in centre?

It's probably best replacing the beams, but am I best replacing them with brick beams for longevity?

And I guess the most important question is, would this be an expensive job if I got a professional in to do it?

Appreciate your time in writing your replies.


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