No gap is too small for Japanese knotweed damage to occur

“Can Japanese Knotweed grow through concrete?” is a very popular question that is asked regarding Japanese Knotweed, especially in light of how many individuals wish to protect their properties and grounds.

Whilst we all know this weed is virulent and unrelenting in its spread and growth around the UK and other countries, the simple answer is …. NO.

It does not have the force to break through brick or concrete. What it does do, though, is exploit cracks and fissures in buildings as its roots expand and seek out moisture to fuel its growth. Once they are in these structural weaknesses, they will naturally expand and this may cause the surrounding concrete to shatter.

No plant root can directly penetrate a sealed surface, which is why root barrier membranes can be so effective.

Whilst the media have whipped up many stories over the years of how Japanese knotweed has taken over properties and has been painted as the villain that has destroyed many buildings, it is unable to grow through an impermeable surface like concrete. Therefore, if your property including walls, paths and drains are structurally sound, then you have nothing to fear.

If left untreated Japanese Knotweed can grow rapidly, by up to 10cm a day during the summer months. Pushing its self through the cracks in concrete within your walls, paths, drives and foundations.

Does Japanese Knotweed grow through concrete – really?

Japanese knotweed routinely makes such headlines due to its ubiquity in urban areas and its potentially damaging effect on buildings. However, much of this is considerably overhyped and far from the truth.

That being said, the perception of harm caused by the presence of Japanese knotweed in a neighbourhood does cause a significant blighting effect, which professional bodies like the Property Care Association (PCA) are trying hard to counter.

With its ability to grow up to 10cm a day during summer and left untreated it will push through these cracks within the concrete, cavity wall or drain and lead to inevitable structural damage.

Once Japanese knotweed has been identified within the cracks or fissures of your concrete it is advisable to act quickly to avoid irreversible damage to your building structure or substrates.

Japanese knotweed exploiting a crack
Japanese knotweed exploiting a crack

Can it force its way through concrete?

The force that Japanese knotweed expels is considerable and it is here that the problem lies. If you have weak or broken concrete with cracks and fissures, this will be the point at which the weed can attack your buildings and use these established footholds to exploit its growth due to the ability to collect moisture and feed its growth.

So, in the vast majority of Japanese knotweed cases, no structural harm is done by the growth. In fact, the type of damage described to the property is more often caused by many other plants that have deep or woody roots.

Insurance claims and remedial works due to subsidence from tree roots are much more significant than any such issues caused by knotweed.

Like any other weed or plant, it needs water and light to continue to grow and flourish, so it’ll be sure to fight its way through weak spots in walls, roads, tarmacs, joints and even concrete. If a trickle of water can pass through a crack, then so can Japanese knotweed, so if you notice a knotweed issue, it’ll need a rapid response.

A word of caution: DIY efforts to rid Japanese knotweed from your broken concrete, wall or drains can ultimately fail if the structural problem is not addressed correctly. Likewise, simply spraying to remove the weed will not solve the problem as the weed has a large root network and it will keep sending new shoots up to replace those that have been chopped down or sprayed above ground.

You will need to have sound and solid concrete at the very least, and at worst you will need to call in an expert to eliminate the problem once and for all.

knotweed growing through a cracked wall
knotweed growing through a cracked wall

Want to know more?

Knotweed Removal aims to provide the most up to date information, help and advice for YOU to make informed decisions. If you are unsure or uncertain on how to proceed, please reach out to us and we will gladly come back and advise you as best we can.

Governmental advice can be found here and the UK law covering the removal of Japanese Knotweed as stated under the Wildlife and Countryside Act 1981 can be found here.

The best means to contact us is via our email – knotweedremovaltips@gmail.com

Do not forget we have a library of blogs covering many areas relevant to Japanese Knotweed, our free downloadable How-to Guides and Product Reviews on the latest methods being employed to eradicate or remove Japanese Knotweed.

Knotweed Removal, UK

SaleBestseller No. 1
Roundup Tree Stump Weedkiller, Super Concentrate 250 ml
  • Kills ivy japanese knotweed, saplings, brambles and nettles to the root
  • Kills up to 16 tree stumps
  • Contains a reusable pipette for specialist treatment of japanese knotweed
  • Kills the roots so weeds don't come back
  • Degraded in the soil by micro organisms
Bestseller No. 2
Bayer Garden 2 x Path, Patio & Drive Weed Killer & Watering Can Set - 3 x 8g Sachets per pack treats upto 75sqm - Kills Ground Elder, Nettles, Docks, Couch Grass & Japanese Knotweed.
  • This exclusive twin pack and 9L Watering Set is everything you need for clearing weeds from paths, patios and rives including areas of tarmac, concrete and block paving.
  • Kills tough weeds and their roots including: Ground Elder, Nettles, Docks, Couch Grass, Japanese Knotweed, Brambles, Bracken & Ivy.
  • Each box contains 3 x 8g Simple ready measured soluble doses and treats up to 75sqm. Apply at any time when weeds are showing green leaf and are actively growing.
  • Sold with our durable 9L or 2 gallon capacity galvanised steel watering can with removable brass rose. Colour cannot be guaranteed. Watering can will be randomly picked and despatched.
  • Keep children and pets away from treated areas until the spray has dried.
Bestseller No. 3
Bayer Garden 2 x Path, Patio & Drive Weed Killer - 3 x 8g Sachets per pack treats upto 75sqm - Kills Ground Elder, Nettles, Docks, Couch Grass & Japanese Knotweed.
  • Ideal for clearing weeds from paths, patios and rives including areas of tarmac, concrete and block paving.
  • Kills tough weeds and their roots including: Ground Elder, Nettles, Docks, Couch Grass, Japanese Knotweed, Brambles, Bracken & Ivy.
  • Each box contains 3 x 8g Simple ready measured soluble doses and treats up to 75sqm.
  • Apply at any time when weeds are showing green leaf and are actively growing.
  • Keep children and pets away from treated areas until the spray has dried.
Bestseller No. 4
Rootblast 360 5L Pump Sprayer Glyphosate Weedkiller 1L with integral measuring device Pair of Gloves 1L makes up to 50L
  • Contains 360 g/l glyphosate, The same as most Professional Grade Herbicides.
  • For use on unwanted vegetation and areas not intended to bear vegetation.
  • First signs of control, a yellowing of the leaves, may take from a few days to 2-4 weeks to appear.
  • 1 Litre of 360 g/L makes 50 litres of standard ready to use glyphosate weed killer
  • Comes with a pair of gloves, 5L Pump Sprayer and integral measuring device. NOTE: The Colour and brand of the sprayer may vary due to stock availability

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