Neighbours tree roots starting to push new wall

ProStuart

Hi,

We have done some work in our back garden where we needed to lower our ground level by around 2-3 feet and after doing so, we built a new wall around 5ft high - reinforced breeze blocks - this was around 6 months ago.
Our neighbour has an established leylandi tree at the end of their garden on their side of the wall and we've noticed our new wall is starting to be pushed out due to the tree roots.
I understand that even cutting down a tree, it takes years for the roots to stop growing/expanding so does anyone have any ideas what to do about the wall in the meantime? 
Thanks

weeg

Sounds like your wall wasn't strong enough. Who designed it? a tree can't grow enough in 6 months to push over a properly designed retaining wall. (Especially if those are winter months).

I'm also not sure why you think your alterations should mean you get to cut down someone else's tree? So my advice to you is to get the wall rebuilt, properly this time. Sorry, I know that sounds snarky.

ac198179

I agree with weeg, if you asked me to chop down a tree in my garden to fit in with a structural change you had made in yours, I'd be telling you exactly where to go! I also think the problem isn't the tree, but the wall itself.

ProStuart

Thanks weeg - bearing in mind I'm a layman when it comes to how a wall should be built, I'm completely dependent on the builder I've had do the extension works on our house (2 storey, 5m x 10m) over the last 9 months.  I wouldn't know what a good wall is vs a bad one but it was laid on full foundations and the blocks are laid flat rather than on their side so it's a 9 inch thick wall with a gravel backfill behind it.
How would you move forward?

TELLIT01

Tree roots would not grow enough in 6 months to push a wall, no matter how badly the wall was constructed.  The problem is far more likely to be caused by the pressure of the soil against the wall combined with the amount of rain we've had in the past few months.

weeg

I can't think in inches. And breeze block is a meaningless term, imo. There's a world of difference between a 10N block and a 3.6, but both might arguably be called breeze block. (rant over!)

Gravel backfill is good, because lack of drainage is often the problem. It's hugely dependant on what the soil is, but at 900mm I'd want to be seeing your wall 440mm, min at the base, stepped in by one brick width every 400mm or so, so it's narrower at the top. A good rule of thumb is that a retaining wall should be 2/3 the width of the height it's retaining.

As to how to fix it, that would depend on  how it's failing - is the whole thing sling forwards? Rotating forwards? is it the masonry cracking? Different failure mechanisms have different solutions. Often adding another skin of engineering brick to the front and tying it back will do the job.

I'd go back to who built it and tell them it's failing and see what they say.

TELLIT01

Weeg, many people use 'breeze block' as a generic term for any concrete blocks, much like people use 'Hoover' for any vacuum.  Unless a person is in the trade it's unlikely they will know the difference between types of block.

stuart45

My wife still calls them breeze blocks, even though they haven't been made for years. I built a retaining wall next to 4 Leylandii, but it was much thicker than yours at 18inch(440mm). 
How was the blockwork reinforced?

Ganga

Not related to this particular thread BUT if someone planted Leylandi trees on your border can you legally dig down on your own land and cut /remove the roots if they are causing damage to your property , IE sucking the moisture out of the soil under your foundations.

twopenny

But if the OP has built the wall knowing the tree was established there  that is their problem.

Also even if your neighbour cut their tree down the roots would shrink and the soil around them causing your wall to move anyway.

It's the wall you need to sort out, not the tree.

weeg

TELLIT01 said:

Weeg, many people use 'breeze block' as a generic term for any concrete blocks, much like people use 'Hoover' for any vacuum.  Unless a person is in the trade it's unlikely they will know the difference between types of block.

I know - but it still rips my knitting! Because the term means different things to different people and so is essentially meaningless. The use of RSJ for a steel beam is another bugbear, because it's 99% sure that what is being installed is not a rolled steel joist, which is a very specific and rarely used (like, I've seen one once) steel shape. 

Apologies for the digression.