Chestnut posts and concrete...?

[VictorDelta]

We're re-placing a garden pergola made of wood which has seen better days. We were advised to use Chestnut poles for the vertical posts as they last longer than other types of wood - so have bought a set of these together with the appropriate number of bags of PostCrete.

However, we've now been told that chestnut posts are better if just put in the earth rather than using concrete, as the latter tends to make them rot faster (3-4 years v. 15-20 years).

This was news to us! Has anyone else come across this before?

 

[Bonni]

The problem with wood, if it's incased in concrete or soil etc.. the moisture and fungus rots the wood. Ideally, wood should be kept of the ground and even brickwork when, for example, holding the corner of a porch roof up. Usually the wood is spaced off the driveway/brick wall by a short metal rod.

https://www.simplylogcabins.co.uk/gudrum-log-cabins-adjustable-galvanised-post-feet-p211

 

[bernardgreen]

Free standing on 4mm lead sheet, this photo was taken in 1980 and the timber is still in perfect condition 39 years later. ( the lead was trimmed to the exact size of the post afte the phot was taken.

 

[VictorDelta]

Thanks for your replies. However, because this is a rustic pergola, the wooden posts have to go into the ground, with or without concrete round the base.

My query was really about whether Chestnut - a hard wood - will rot faster in concrete than without...?

 

[HERTS P&D]

Bernard, was it black and white in 1980?



Andy

 

[bernardgreen]

Bernard, was it black and white in 1980?

The picture was taken by a photographer who was taking photos for one of the suppliers we used. ( The house was a full DIY self build )

will rot faster in concrete than without...?

Wood ( soft or hard ) rots when there is air and damp, wood in water logged ( no air ) soil usually rots much slower than wood in damp soil.

As regards timber into concrete the rate of rot depends on how much and where damp and air can get to the timber.

 

[scbk]

Thanks for your replies. However, because this is a rustic pergola, the wooden posts have to go into the ground, with or without concrete round the base.

My query was really about whether Chestnut - a hard wood - will rot faster in concrete than without...?

Living in the north of Scotland, I've never used chestnut posts*
Bare in mind Horse and Sweet chestnut are two very different timbers.
And with sweet chestnut, it apparently makes a big difference if it is summer or winter felled (and also the amount of sapwood).


IMO timber posts set in concrete isn't a great combination

If you wanted, you could apply preservative to the posts before they go in the ground.




*I once built a bench with 4 horse chestnut logs set in the ground as legs, as far as I know it's still there.

 

[lostinthelight]

When timber is referred to as “Chestntnut” it invariably means Sweet Chestnut which is high in tanning and very rot resistant. Horse chestnut by contrast is susceptible to decay so rots easily
I prefer to ram stone around posts which lets water drain and allows further ramming/tightening if the ground shrinks
Edit:
The disadvantage of ramming is it takes a little more time and skill .

 

[Notch7]

Thanks for your replies. However, because this is a rustic pergola, the wooden posts have to go into the ground, with or without concrete round the base.

My query was really about whether Chestnut - a hard wood - will rot faster in concrete than without...?

thereisnt much difference -chestnut will rot in soil and concrete.

wrap the bit below ground and just a bit above with bitumen flashband or use a post saver
it can help the posts last 20 years.

https://www.postsaver.com/

https://www.toolstation.com/bostik-flashband/p44914