Stuff growing out of walls - what is the definitive answer?

[modernrail]

Hi. There are posts from time to time about this subject but I don’t think there have been definitive views on the point. I wondered if there might be one. This is with no prejudgment on my part. I am genuinely interested in the take of any structural engineers.

The attached photo shows things growing out of the viaduct that holds the overground and Southern lines at Peckham Rye.

To my untrained eye that looks like a lot of foliage. I can’t believe it is not adversely impacting what is a critical viaduct in terms of the London network.

- is that foliage damaging the viaduct?
- how bad is any damage likely to be?
- what are the long term maintenance and cost implications of allowing this growth to occur?
- if it is a problem, why is NR allowing this to occur. Budget can’t be a valid reason if this sort of thing is seriously undermining critical structures. Maybe it is not a problem?

 

[HSTEd]

- if it is a problem, why is NR allowing this to occur. Budget can’t be a valid reason if this sort of thing is seriously undermining critical structures. Maybe it is not a problem?

If the money does not exist to remove the vegetation, the money does not exist.

Getting at that vegetation will not be cheap, and killing it off is not likely to help the structure of the viaduct as the roots etc start to rot away.

 

[Mcr Warrior]

If the money does not exist to remove the vegetation, the money does not exist.

The issue of scrimping on vegetation management, often discussed on here, does seem like a penny wise, pound foolish, 'false economy' in the long run.

 

[swt_passenger]

I think there should be more visibility of the problem and solution if RAIB actually investigated when there are real failures, such as on the Nine Elms Viaduct on the approach towards Waterloo. I’m sure streetview images of the ‘before’ condition of that stretch were fairly similar to the earlier attachment.

I suspect the Nine Elms collapse was downplayed a bit, as it happened in a possession, but I thought RAIB can still do a full investigation on the basis that it ‘could have been worse at another time’.

 

[Merle Haggard]

Is it not the case that the weedkillers which permanently destroyed the roots (2-4-5T Dioxin, for instance) are now banned, and the replacement only kills the vegetation not the roots?
It seems to me that damage by the roots of plants will affect a lot of infrastructure, not just on the railways. Travelling around Devon by Network Rail and Dartmouth Steam Railway there seemed to be a lot of walls on and off the railways with that plant with pretty-looking pinky/purple blossom getting rooted into the mortar line of walls.

 

[jupiter]

I don’t like to disagree but there’s always money, it’s just being spent on other things.

The issue is raising the priority of these remedial works, which means not doing something else.

 

[XCTurbostar]

- is that foliage damaging the viaduct? Buddleia's root systems can weaken materials and thrive on wet mortar so yes almost certainly.
- how bad is any damage likely to be? This Buddleia has been here for over 5 years so the roots are likely extensive and well situated.
- what are the long term maintenance and cost implications of allowing this growth to occur? Almost none in the first few years but as the structure weakens, excessive loads will encourage cracking and thus eventual failure.
- if it is a problem, why is NR allowing this to occur. Budget can’t be a valid reason if this sort of thing is seriously undermining critical structures. Maybe it is not a problem? It is only viewed as a visual issue since Buddleia is well positioned across the entire railway, it doesnt take long for it to re-grow even after re-ballasting or removal.

 

[Geeves]

When something inevitably collapses with a train on it one day something will be happen, no doubt there will be an enquiry as why its become so horrendous and whos to blame

The viaducts throughout Manchester are in a terrible state as they are everywhere.

 

[Mogster]

Is it not the case that the weedkillers which permanently destroyed the roots (2-4-5T Dioxin, for instance) are now banned, and the replacement only kills the vegetation not the roots?
It seems to me that damage by the roots of plants will affect a lot of infrastructure, not just on the railways. Travelling around Devon by Network Rail and Dartmouth Steam Railway there seemed to be a lot of walls on and off the railways with that plant with pretty-looking pinky/purple blossom getting rooted into the mortar line of walls.

I thought the same when coming to this thread.

It’s not just the railways, lots of local infrastructure now has a vegetation problem. The weed killers that would have been used historically once a year have been banned, there seems to be no answer.

 

[Annetts key]

I'm not a structural engineer but have carried out stone and brick wall repair on my own property.

Even the humble dandelion root can damage walls and stone and brick structures. The plant speeds up the damage caused by water. And makes it easier for water to get deeper into the brick or stonework. If/when the water freezes, further damage is done.

Tree and bush roots can get into cracks and mortar. As the roots force the cracks to expand, they can grow even deeper into the structure. Once the mortar has been penetrated, the roots can then use the mortar to expand within the structure.

- is that foliage damaging the viaduct? Yes.
- how bad is any damage likely to be? Extensive if the vegetation has been there for years. It may not have reached the stage where the structure is in danger of collapse. But parapet walls are likely to need to be completely rebuilt at the very least.
- what are the long term maintenance and cost implications of allowing this growth to occur? Eye-wateringly expensive. The longer that maintenance and repair work is put off, the greater the cost. Ultimately a new structure may be needed.
- if it is a problem, why is NR allowing this to occur. Budget can’t be a valid reason if this sort of thing is seriously undermining critical structures. Maybe it is not a problem? It's easy to make the decision to defer doing any work. Especially if the latest report says that it's currently safe. And unseen damage will may be overlooked. Then when it's found how bad it is, the costs to up and the project overruns.

Also, under Network Rail, some comes under the responsibility of the "Off-Track" organisation. While bridges, viaducts etc. are the responsibility of the structures organisation.

I used to work for the railway. I know that the S&T had difficulty getting vegetation removed from bridges and viaducts that was obscuring signals. Never mind anyone even trying to deal with the rest of the vegetation on structures.

 

[MadMac]

I refer you all to Frank L. Lucas’ poem “Beleaguered Cities”: https://allpoetry.com/Beleaguered-Cities-

 

[Xenophon PCDGS]

There was structural damage that led to an infrastructural collapse at Northwich railway station. I heard at the time that plant problems had led to this, but can anyone on this thread confirm the actual cause.

 

[Mcr Warrior]

There was structural damage that led to an infrastructural collapse at Northwich railway station. I heard at the time that plant problems had led to this, but can anyone on this thread confirm the actual cause.

Lack of effective vegetation control, it would seem.

Northwich: ‘Lessons learned’ after station collapse - MP - BBC News

An MP meets with rail bosses after the collapse of a station roof three years ago.

www.bbc.co.uk

Extract...

Mid Cheshire MP Andrew Cooper said a report from the Office of Road and Rail (ORR) found the cause of the collapse at Northwich Station to be a lack of vegetation control.

 

[Lloyds siding]

Yes, I can confirm this. I visited Northwich a matter of weeks before the accident. I was shocked by the large Buddleia growing on the roof, and the leaning masonry that it was causing, so shocked that I took a picture. But it appears that I no longer have a copy after the phone stopped working...
What was really shocking was that there was building work going on at the station at the time, but not affecting the area with the Buddleia, so it looked as though its presence was being ignored.

 

[Envoy]

Buddleia bushes are growing en mass in and around the Cardiff Canton depot and Network Rail do nothing about it. Right now in winter, the seeds from the summer flowers are blowing off to redistribute and take root wherever.

What Network Rail should be doing now is sending guys out to cut all these Buddleias down to ground level - carefully bagging the seed heads and taking them away for burning. Then, when growth starts again in the spring, let them grow to about a foot and spray them with weedkiller late in the day (when no rain is forecast). The poison will be absorbed by the leaves overnight and go down to knock out the roots. At the same time, they should look for and deal with any of the seedlings that have taken root to produce new plants and spray them.

Doing nothing is not an option. If you see all those mauve flowered bushes in summer, it indicates that Network Rail are indeed doing nothing and they will turn to seed to make the problem even worse.

 

[Xenophon PCDGS]

It will take something of a Governmental fully-funded operation to nationally eradicate the problem. Perhaps it should be brought to the attention of the new/replacement Minister in whose remit this problem lies.

 

[Harpo]

Even the humble dandelion root can damage walls and stone and brick structures. The plant speeds up the damage caused by water. And makes it easier for water to get deeper into the brick or stonework. If/when the water freezes, further damage is done.

Exactly. Known as the freeze/thaw cycle.

 

[DustyBin]

There’s some good answers above.

Removing the vegetation is the relatively easy part; carrying out the follow-up repointing and masonry repairs is when it gets really expensive. Looking at the photograph of Peckham Rye above, it’s going to cost hundreds of thousands of pounds to deal with that lot (at least), and considerably more if the works become more structural in nature. That’s not to say it should be ignored, but is why it probably will be!

 

[Amlag]

Much of the cause is down to ‘Remote in more ways than one’ Management who fail to understand and prioritise
an unglamorous but essential responsibility in keeping structures, stations, walkways and cesses etc free of scrub, brambles, trees and the dreaded and very damaging Buddlia.

A very good example of a well cared for, tidy and weed, let alone buddleia bushes, FREE traincare depot is that at
Salisbury Managed by SWR; it gives a very good impression of care and even ‘pride in the workplace’ to any passenger making an effort to take a break from their hand held device, and look out of the train window as it passes by.

 

[simonw]

Hi. There are posts from time to time about this subject but I don’t think there have been definitive views on the point. I wondered if there might be one. This is with no prejudgment on my part. I am genuinely interested in the take of any structural engineers.

The attached photo shows things growing out of the viaduct that holds the overground and Southern lines at Peckham Rye.

To my untrained eye that looks like a lot of foliage. I can’t believe it is not adversely impacting what is a critical viaduct in terms of the London network.

- is that foliage damaging the viaduct?
- how bad is any damage likely to be?
- what are the long term maintenance and cost implications of allowing this growth to occur?
- if it is a problem, why is NR allowing this to occur. Budget can’t be a valid reason if this sort of thing is seriously undermining critical structures. Maybe it is not a problem?

The buddleia will be damaging the brick work. However, the cost of removing will be substantial and this will have to be balanced against the cost of leaving it and only repairing when essential to do so. This is will be the major reason why it has been left - the future discounted cost is estimated to be less than the current cost.

 

[Trainbike46]

The buddleia will be damaging the brick work. However, the cost of removing will be substantial and this will have to be balanced against the cost of leaving it and only repairing when essential to do so. This is will be the major reason why it has been left - the future discounted cost is estimated to be less than the current cost.

While I'm sure some decision makers view it this way, that is based on a lot of assumptions that I wouldn't be happy with making myselfd

 

[Merle Haggard]

Just to be clear; the 'pinky-purple' flowering plant that I mentioned above that I saw in the early stages of causing havoc in Devon is NOT Buddleia. I don't recollect seeing it in the past but it suddenly seems widespread; it has jumped down my street, garden to garden. I think some of my neighbours may have left it because 'it's a pretty colour' but I've tried to extinguish it in my patch - quite hard because it produces a lot of seed throughout the Summer..

 

[Winthorpe]

Just to be clear; the 'pinky-purple' flowering plant that I mentioned above that I saw in the early stages of causing havoc in Devon is NOT Buddleia. I don't recollect seeing it in the past but it suddenly seems widespread; it has jumped down my street, garden to garden. I think some of my neighbours may have left it because 'it's a pretty colour' but I've tried to extinguish it in my patch - quite hard because it produces a lot of seed throughout the Summer..

Are you thinking of Himalayan balsam? It's a huge problem near me in South Manchester.

Himalayan balsam / RHS

Himalayan balsam is an annual plant with scented flowers in shades of pink and purple. Introduced to Britain as an ornamental garden plant, it is now considered a problematic weed, particularly along watercourses.

www.rhs.org.uk

Himalayan balsam | The Wildlife Trusts

As its name suggests, Himalayan balsam is from the Himalayas and was introduced here in 1839. It now an invasive weed of riverbanks and ditches, where it prevents native species from growing.

www.wildlifetrusts.org

 

[Dr Hoo]

Buddleia bushes are growing en mass in and around the Cardiff Canton depot and Network Rail do nothing about it. Right now in winter, the seeds from the summer flowers are blowing off to redistribute and take root wherever.

What Network Rail should be doing now is sending guys out to cut all these Buddleias down to ground level - carefully bagging the seed heads and taking them away for burning. Then, when growth starts again in the spring, let them grow to about a foot and spray them with weedkiller late in the day (when no rain is forecast). The poison will be absorbed by the leaves overnight and go down to knock out the roots. At the same time, they should look for and deal with any of the seedlings that have taken root to produce new plants and spray them.

Doing nothing is not an option. If you see all those mauve flowered bushes in summer, it indicates that Network Rail are indeed doing nothing and they will turn to seed to make the problem even worse.

Noting the comments below about how Salisbury depot is very tidy, can anyone clarify whether vegetation management within depots such as Canton is actually a Network Rail responsibility (rather than the depot ‘owner’/lessee, e.g. Transport for Wales or whoever)?

 

[Clarence Yard]

It is a depot responsibility. The only problem comes if any structure is next to a running line and a possession/isolation needs to be taken.

 

[Dr Hoo]

It is a depot responsibility. The only problem comes if any structure is next to a running line and a possession/isolation needs to be taken.

Thank you for clarifying.

 

[Envoy]

Buddleia bushes are growing both within the Canton depot and outside the boundary fence on Network Rail land and sprouting up between tracks on the approaches to Cardiff Central station. They need dealing with because the seeds just blow and take root in the ballast or worse still, lodge in masonry which they can rip apart. They can also take root in cracks in houses near the railway.

Click this link and a Google Map will appear of the Cardiff Canton depot. On the south side, you will see a triangle. Within that triangle are masses of buddleia bushes - all flowering and then producing seeds that blow and root amongst the tracks and in the depot. As this area is not in the working area of the railway, Network Rail seem to think that it does not matter. It does matter because even if they get rid of the bushes growing in the working area of the railway, the seeds from the land in the triangle will just blow in and cause more buddleia to sprout up and hinder operations.

As I said earlier, in the case of Canton, they should go in now during the winter, cut down those buddleia bushes and set fire to them. Then, when they re-sprout in the spring, let them grow to about 1 ft and then spray the leaves with weedkiller which will go down into the roots and kill them.

Perhaps Network Rail think they are the Butterfly Conservation Society? Be in no doubt, these are pest plants.

Here is a photo of the Buddelia buses growing by the Cardiff Canton depot complete with seeds heads which the winter winds are now dispersing to create new plants in 2025.