Weeping Willow, should it stay or should it go?

[MDC]

I have a plot that has a [say] 30 year old weeping willow on the north side of the existing house, and a group of oak trees on the south side. I like trees, so want to keep them all, but owing to the proposed size of my design of replacement dwelling, something has to give.

 

The gossip is Weeping Willows are not welcome on building sites. They have shallow roots that spread a considerable distance. Funny thing is, the existing house [built on piles 70 years ago] is unaffected. The tarmac driveway shows no evidence of roots, so I'm in two minds. The willow is less than 16 metres from the existing house. It offers a good screen to the neighbours [not close].

 

Is it prudent to remove the willow?

 

[ProDave]

We have several willow trees.  Most of them remained, the Structural engineer and  building control did not raise an eyebrow.  Digging the foundations almost no tree roots were found anywhere near the house footings.

 

In our case it is probably because the willows are either side of the burn so I would suspect that is where you find their water and where most of their roots are concentrated.

[joe90]

I also have several trees close to my build, the BC wanted the oak tree removed but forgot about it and the foundation trench showed no roots so it’s still there. I would a/ wait till the founds are dug, b/ see what BC say. It would be a shame to loose trees if not required.

[saveasteading]

The problem is with big, deciduous trees on shrinkable ground such as clay.

They drink the water in summer, the clay shrinks, and the building moves. Then is winter the tree is dormant and the ground expands again.

 

The solution is deeper footings or piles, which you have.

 

For a willow/oak etc on clay, the effect is up to 24m from the footings.   At that distance a 0,9m deep footing  may need to be 1m (approx from memory).

But very near to the building it may require 4m deep foundations.

 

If there is a stream between, or rock beneath, or multiple other variables' then this doesn't apply.

It is important so check it out. NHBC is the easiest resource (online) for the guidelines, using the BS graphs  for "Building Near Trees"

[saveasteading]

9 hours ago, MDC said:

Is it prudent to remove the willow?

No. Once cut down, its effect on the ground will continue, as the ground becomes wet and the ground expands. 

Unless you can leave it a season to stabilise.

 

Don't assume that the BCO understands this. It will be your problem, not theirs.

I once had a bco walk round the site with me looking at founds. He had no comments about the differing depths , sometimes quite deep when close to large trees.

On gentle questioning it became clear that he was unaware of the subject.

 

But what are your ground conditions?

Clay/rock/gravel/ an old landfill???

[MDC]

9 hours ago, saveasteading said:

No. Once cut down, its effect on the ground will continue, as the ground becomes wet and the ground expands. 

Unless you can leave it a season to stabilise.

 

Don't assume that the BCO understands this. It will be your problem, not theirs.

I once had a bco walk round the site with me looking at founds. He had no comments about the differing depths , sometimes quite deep when close to large trees.

On gentle questioning it became clear that he was unaware of the subject.

 

But what are your ground conditions?

Clay/rock/gravel/ an old landfill???

That's interesting. I have the impression you're suggesting the willow provides a service, which will carry on for a season and then stop, so the soil will be wetter in the future, which means it will act differently after the house is built [if it's built within a year of felling the tree]. 

 

The ground is clay. The tree and the proposed house are at the highest point on the land.

[MDC]

18 hours ago, ProDave said:

We have several willow trees.  Most of them remained, the Structural engineer and  building control did not raise an eyebrow.  Digging the foundations almost no tree roots were found anywhere near the house footings.

 

In our case it is probably because the willows are either side of the burn so I would suspect that is where you find their water and where most of their roots are concentrated.

This willow is at the high point of the land! There is no stream/burn anywhere. I'm told it was bought from Woolworths at a cost of £2.50, and it'll cost a fair bit more to remove it.

[MDC]

17 hours ago, joe90 said:

I also have several trees close to my build, the BC wanted the oak tree removed but forgot about it and the foundation trench showed no roots so it’s still there. I would a/ wait till the founds are dug, b/ see what BC say. It would be a shame to loose trees if not required.

Interesting you'd wait for BC. Round our way people take the trees out to avoid TPO's before the build. 

[joe90]

29 minutes ago, MDC said:

Interesting you'd wait for BC. Round our way people take the trees out to avoid TPO's before the build. 

Just depends if you want it gone or not!!!

[Ferdinand]

For amenity value, it would be remove the willow and keep the oaks, as the willow ha a short lifetime and the oaks should last hundreds of years.

 

Is there a survey indicating remaining lifespan?

 

Also weeping willows have a habit of growing sideways substantially.

 

F

[saveasteading]

The effects of a willow or oak are much the same as both grow to about 24m and take up huge amounts of water, and clay shrinks. The foundations would be designed for the mature height.

 

Apart from the shrinkage in summer, another issue us that a large tree looks out of place and grows lopsided if very close to a building. Also sheds leaves and sticks, perhaps into the gutter.

 

The main benefit is obvious, that trees are a good thing. But also,  If to the south of the building they shade and cool in the summer but allow light in winter.

 

A willow on clay will need foundations about 2.5m deep. Not the end of the world. 

If it does / they do fall over suddenly  then you need a wet winter and spring for the ground to recover IF there are roots to the house. Ignoring this can cause immediate heave of the foundations.

[MDC]

3 minutes ago, saveasteading said:

The effects of a willow or oak are much the same as both grow to about 24m and take up huge amounts of water, and clay shrinks. The foundations would be designed for the mature height.

 

Apart from the shrinkage in summer, another issue us that a large tree looks out of place and grows lopsided if very close to a building. Also sheds leaves and sticks, perhaps into the gutter.

 

The main benefit is obvious, that trees are a good thing. But also,  If to the south of the building they shade and cool in the summer but allow light in winter.

 

A willow on clay will need foundations about 2.5m deep. Not the end of the world. 

If it does / they do fall over suddenly  then you need a wet winter and spring for the ground to recover IF there are roots to the house. Ignoring this can cause immediate heave of the foundations.

Yes, this willow has more growth away from the existing house.

 

If we take the willow out next week, and achieve planning by next May, in theory the foundations will be in by July, and so on we go.

 

The willow has to go, and the south side oaks stay. Thanks for your advice.

[saveasteading]

How far to the oaks?

[patp]

We removed some hawthorn hedging and our bco made us dig extra deep footings to compensate for the change in the soil movement that he predicted would happen. If we had left the hedge he would probably made us dig extra deep to keep the roots out!

[MDC]

1 hour ago, saveasteading said:

How far to the oaks?

With the willow gone, we'll move the design across, so 35+ metres or so

[MDC]

1 hour ago, patp said:

We removed some hawthorn hedging and our bco made us dig extra deep footings to compensate for the change in the soil movement that he predicted would happen. If we had left the hedge he would probably made us dig extra deep to keep the roots out!

I'll assume deeper footings

[joe90]

10 minutes ago, MDC said:

I'll assume deeper footings

Don’t assume anything, let the BCO tell you what he wants.

[Iceverge]

Piles have worked for 70 years on your soil. 

 

It might be a good place to start re footings? 

[MDC]

3 hours ago, Iceverge said:

Piles have worked for 70 years on your soil. 

 

It might be a good place to start re footings? 

Fair point

[saveasteading]

4 hours ago, joe90 said:

let the BCO tell you what he wants.

I don't agree. Get it right as it is your house. Then the bco will agree anyway.

 

Oaks at 35m have no effect.

Hawthorns have very little effect.

[joe90]

1 hour ago, saveasteading said:

Get it right

How

1 hour ago, saveasteading said:

Then the bco will agree

So why not listen to what he requires? If he specifies an SE or expert to decide then so be it. With mine the BCO knew the area so knew what was required without consulting others.

[PeterW]

Sorry did we find out how far this willow is from the house ..?

 

Also - if you’re on piles today then it’s for a reason.. I would be more concerned with this first 

[Andehh]

We had foundations about 2m deep 13m ish from a mature willow. Had to install heave protection as well. Found no real rootage to speak of in the trench. 

[Andehh]

Also worth saying, mature trees are pretty rare in domestic gardens, they are a real feature / add value! I'd avoid removal. 

[MDC]

11 hours ago, PeterW said:

Sorry did we find out how far this willow is from the house ..?

 

Also - if you’re on piles today then it’s for a reason.. I would be more concerned with this first 

Less than 16 metres.