Silver birch, possible subsidence, remove or reduce?

[old-home-owner]

We have an old home (about 350 years) and in the past few years, there has been some movement in the front wall of the house. The movement is across the front of the house, from the downpipe to the bench in the photo.  Looking at the photos, the drain below the downpipe was broken, and possibly has been for the past 15 years (now fixed). It runs slightly downhill from the downpipe to the bench, so rainwater could have spread across the front wall.

 

We have a silver birch that's 5m from the downpipe and one of its roots had found the broken drain and intertwined itself with the brickwork just below ground. We've had a structural engineer round for an informal 'first look', and he said clearly the drain will have contributed to the movement in the wall, but also, possibly the tree. He said on balance, the tree has probably had some contributing factor, and it is was his house, he'd remove it.  He said I could have soil analysis done to assess whether there is desiccation, and whether it's caused by the tree roots, but that would cost more and the outcome may be the same - remove the tree. Given I've found the root in the photo, it wouldn't surprise me if there were other roots reaching further along the front wall.

 

We are near Dunstable Downs and the ground is chalky, which I know wouldn't normally be associated with subsidence.

 

So, my dilemma is whether to remove the tree and have peace of mind that it can't contribute to any subsidence (whether it has done or not), whether to reduce the crown in some way to reduce the draw that the tree has on the water in the ground, or whether to leave the tree. The tree is very pretty and ideally, I'd leave it untouched, but OTOH, I don't want to risk any more damage to our home. The structural engineer said that if I was going to remove it, he'd do it over the course of a couple of years to reduce any chance of heave.

 

I know it's hard to comment from online photos, but what are people's thoughts on this?  I'm erring on the tree removal side (sadly), but would want to replace it with something that wouldn't grow as large.

[matt padden]

If the drains been broken for 15yrs I'd have thought that was the cause of any movement. That tree would only have been a sapling then. That root has probably latched on to a steady drink in the subsequent years.. Why not excavate to see if there are any other substantial roots but if it's just that one cut the root back a few meters from the house. I doubt it will affect the tree much and if it does fell it then. Seeing as you've already started digging out why not put in some sort of root barrier.

Or fell it and plant a Monkey Puzzle 6ft from the front of the house.

[Squaredy]

1 hour ago, old-home-owner said:

We have an old home (about 350 years) and in the past few years, there has been some movement in the front wall of the house. The movement is across the front of the house, from the downpipe to the bench in the photo.  Looking at the photos, the drain below the downpipe was broken, and possibly has been for the past 15 years (now fixed). It runs slightly downhill from the downpipe to the bench, so rainwater could have spread across the front wall.

 

We have a silver birch that's 5m from the downpipe and one of its roots had found the broken drain and intertwined itself with the brickwork just below ground. We've had a structural engineer round for an informal 'first look', and he said clearly the drain will have contributed to the movement in the wall, but also, possibly the tree. He said on balance, the tree has probably had some contributing factor, and it is was his house, he'd remove it.  He said I could have soil analysis done to assess whether there is desiccation, and whether it's caused by the tree roots, but that would cost more and the outcome may be the same - remove the tree. Given I've found the root in the photo, it wouldn't surprise me if there were other roots reaching further along the front wall.

 

We are near Dunstable Downs and the ground is chalky, which I know wouldn't normally be associated with subsidence.

 

So, my dilemma is whether to remove the tree and have peace of mind that it can't contribute to any subsidence (whether it has done or not), whether to reduce the crown in some way to reduce the draw that the tree has on the water in the ground, or whether to leave the tree. The tree is very pretty and ideally, I'd leave it untouched, but OTOH, I don't want to risk any more damage to our home. The structural engineer said that if I was going to remove it, he'd do it over the course of a couple of years to reduce any chance of heave.

 

I know it's hard to comment from online photos, but what are people's thoughts on this?  I'm erring on the tree removal side (sadly), but would want to replace it with something that wouldn't grow as large.

If that is just a normal birch tree it is still in its childhood.  In which case it is way too close to the house.  If you are worried now, what about in 20 years when it is approaching maturity?  I am sure 10 experts will give you 11 different opinions but why take the risk?  If it isn't protected thank your lucky starts for this, and replace it with something appropriate for the location.

 

Chalk bedrock as you say is not going to swell or shrink with moisture or lack of it.  But in some areas the chalk is capped by clay, which will.  The photo does not show clay, but what is under the foundations?

 

[GarethM]

I'd be more worried about the rainwater not having any actual drainage taking it away from the foundation which on an older building will be very very minimal.

 

That's the real issue after what also looks like a relatively new brick driveway won't have helped.

[Mark Bolam]

Ask your structural engineer why removing it over the course of a couple of years would remove the chance of heave?

Total bullshit.

If it’s going to heave it’s going to heave, staged reduction will only make it heave more slowly.

(It won’t heave).

[Mark J]

Tree roots will ingress in drains where there are defects, they sometimes wrap around the outside of them and make use of the condensation. 

 

I'm not necessary advocating anything here but as Mark Bolam says above, staged removals are a waste of time.
 

You're apparently not on a clay bedrock, whether there are superficial deposits of clay in your area is unknown. 

 

If you aren't on clay soil there is no chance of subsidence.

 

You could determine if your tree is involved in the movement by conducting crack and/or level monitoring once drains have been fixed (assuming there are soils with a clay component below foundation level).

I like your tree, I'd be inclined to keep it too. However it is going to grow and will require occasional pruning. It has a nice shape to it and would accommodate sympathetic pruning to maintain its current size.

If you do decide to fell it I would probably replant a bit further away from your property. 

 

 

 

 

 

Edited March 31 by Mark J

[Stubby]

Dig a proper soak away . 

[old-home-owner]

Wow, lots of replies. Thank you very much, it's appreciated.

 

> If that is just a normal birch tree it is still in its childhood.

 

When we moved in 15 years ago, the top of the tree was level with my eyes when looking out of the bedroom window. It's now about 3 feet higher, so that's the growth I've observed in 15 years. You make a good point though, if it carries on growing for a few more years, it's only going to make me more worried.

 

> I'd be more worried about the rainwater not having any actual drainage

 

Sorry, my photos were misleading - I was trying to show the root in the photos, not the drain. There was a rudimentary drain there, connected to the mains via clay pipes, but part of it had collapsed and it had filled with silt. It was hidden under a flagstone and I never had any reason to suspect it was broken until a couple of months ago. I removed the drain, took those photos, then put in a new drain. This is all working now, connected to the clay pipe you see in the photos, which runs round the house to the sewer at the back.

 

> relatively new brick driveway won't have helped

 

That was put in maybe 8 years ago. I'm not sure why this may be a concern, but happy to listen. There was a broken tarmac path there before.

 

> Ask your structural engineer why removing it over the course of a couple of years would remove the chance of heave?

 

By his own admission, he's not an arborist and was saying that out of caution. I'm happy to receive advice from you guys as this is your area - this is why I'm posting on here. If I end up removing the tree and the opinion on here is that I can remove it in one go, I'd be happy to do that.

 

> If you aren't on clay soil there is no chance of subsidence.

 

I've done a lot of digging to replace gate posts around the property over the years, and I haven't seen any clay. Something caused some movement in the front wall of the house. The only things nearby are the drain and the tree. The drain is obviously a big red flag, but that's fixed now. I'm left trying to decide whether I need to do anything with the tree.

 

> Seeing as you've already started digging out why not put in some sort of root barrier.

 

The digging has all been made good now. I had wondered whether some sort of root barrier would be effective. I wouldn't want to disturb the path, as it's relatively new, so it would have to be maybe 12" into the grass from the path. What would be effective? Dig a trench and stand paving slabs on their ends just below the grass? How deep, 18 inches? This may be the answer.

 

> Or fell it and plant a Monkey Puzzle 6ft from the front of the house.

 

Lol, another pretty tree that I wouldn't want to fell!

 

Can you help me understand the roots I need to be concerned with? The structural engineer admitted he's clearly not an arborist, but his simple understanding is that trees have two kinds of roots. Large ones for structural support (keeping them upright) and a mat of long, thin roots to suck up water. He said it's the smaller ones that you need to worry about.

 

Thanks again for the replies so far.
 

Edited March 31 by old-home-owner
'sewer', not 'mains'

[old-home-owner]

Drain before and after shots, if that floats your boat and you want a break from trees.

 

The old drain was a piece of 4" plastic pipe with half the top cut off, that the down pipe could empty into. That went to a brick built 'elbow'. That led to a clay pipe that was pointing uphill, towards another clay pipe that the end had broken off. It was all completely broken. In that pic, I'm trying to clear the pipe with a hose. You can see the root over the top of the grey plastic pipe. It squeezed under a flagstone and over the pipe.

 

The new drain works. If I lift the manhole cover at the back of the house, I can see rainwater coming from the front now.

Edited March 31 by old-home-owner
more info

[daveatdave]

i think you have sorted 90% of the problem out doing that. the tree is not the problem it's quite a distance away for its size

[Dan Maynard]

Looks like a kind of weeping birch to me, not the kind that's reaching for the sky. I've seen bigger ones closer to the house, I wouldn't personally be in a rush to remove.

 

Other thought, birch can be a git for big black shallow roots disrupting patios and paths, if it's a new path or drive I would make some sort of definite root barrier to stop it renovating.