Bolting or bracing a cracked tree - advice please

[kentjames]

Hey folks

 

I have a client who has a Liquidambar which as a severe crack up one stem. We have already done a reduction on the tree but I am thinking it could benefit from being bolted to stop the crack going any further?

 

I can't seem to find any threads on such techniques and wonder if anyone can help or advice?

 

Questions

 

1/ I'm thinking at least two 10 or 12mm threaded rods with square plates to act as washers and nylock nuts?

 

2/ Does anyone think it should have a cable higher up to support the overall weight as well?

 

3/ I've read on some sites that its best to remove the cambium layer from the area where the plate will sit against the bark? yes or no?

 

Pics hopefully below - the highlighted red oval is the area of the split - see how its pealing away from the tree on the larger scale image.

 

Additional info - a large branch broke out of the tree previously hence the 'hole' in the middle area - this is recovering well and new growth from below is coming up to infill

 

Many thanks in advance! James

[Stephen Blair]

That's a modern day reduction James!

If they want to save the tree, they need to be realistic.

Half it, bolt it like you say and plant it's future replacement at the side. Job done:)

[treeseer]

No BS support standard?

[Gary Prentice]

NOTE Appropriate restraint may be provided by one of the following:

a) flexible restraint (10.4) – the installation of a flexible material, either

synthetic fibre ropes or steel cables, to reduce dynamic loading

on potentially weak structures and thereby to restrain excessive

movement. This operation is normally accompanied by pruning to

reduce the loading on weak structures in the tree (see Clause 7);

 

b) rigid bracing (10.5) – the installation of solid rods or bolts into the

tree to limit movement or to help support a weak structure;

 

10.5 Rigid bracing

COMMENTARY ON 10.5

A rigid brace involves the use of bespoke steel components inserted into

a tree to prevent the independent movement of adjacent parts of the

tree that form a weak structure. This helps to relieve stress on the weak

structure, as in the case of a tight fork with included bark, or a split along

the axis of a stem or branch (10.5.1). Rigid bracing may also be used to

prevent movement of branches where they rub together (10.5.2) or to

brace the walls of a cavity (10.5.3).

Parts of a tree that contain decayed wood are often unsuitable for

bracing together using a rigid system, since the bracing rods are likely to

pull out if the decay spreads into the sound wood in which the rods have

been secured

 

From BS3998:2010

 

I can't assess enough from the photo to offer any opinion. From experience though, I'd also consider the following points.

 

We used rigid braces in these situations, coupled with a cable 2/3 higher in the canopy to limit the stress at the threaded rod. I've no idea how this species compartmentalizes decay. If it's poor, the rod may quickly, in tree terms become inaffective.

 

I did observe that most of the trees that had been "rodded" survived the storm in the late eighties, in that the whole tree failed rather than just stem failure occuring.

 

Shigo did a lot of work on these techniques, so it's well worth researching. The newer boa non-invasive cables seem to be adequate, but again do more research.

 

At the end of the day, in the event of a failure, its your neck on the block. There's lots of aspects to consider and decisions that you need to make. Read everything you can find on the subject. Good luck.

[Lee Winger]

fell it.........

[Andy Collins]

I actually agree with Lee....fell it. Many moons ago we had to rod and brace a large cedar in a park. It cost a fortune to the client....and died anyway. Fell and replant with similar species.

[treeseer]

I actually agree with Lee....fell it. Many moons ago we had to rod and brace a large cedar in a park. It cost a fortune to the client....and died anyway.

Was bracing responsible for death? ...that other thread warned about giving actionable advice based on inadequate info.

 

Tree has an odd structure, even for a liquidambar (fair codit sp.)

 

"Parts of a tree that contain decayed wood are often unsuitable for

bracing together using a rigid system, since the bracing rods are likely to

pull out if the decay spreads into the sound wood in which the rods have

been secured"

 

This agrees w ANSI, which forbids some installations in trees w decay >30%. But using a cable in these areas as a brace is compliant. "Anchors and braces shall not be installed into decayed areas where sound wood is less than 30% of the trunk or branch diameter"

Because a cable is not an anchor or a brace, through-cabling into >70% unsound wood using end-fasteners is compliant w ANSI.

 

Consider the spot above--yellow line-- where the 2 leaders seem to rub. maybe scrape off bark there and press them together with a throughcable, to stimulate grafting?

[Gary Prentice]

I was in Cambridge in the late eighties. Many trees had been previously successfully braced, using the old invasive techniques. We found many trees with cables had uprooted. But significantly with partial failures, cables held the failed limbs and stems up.

 

If the client is keen to retain the tree, I'd go ahead. It may not even need further reduction but you'd have to be the judge of that. I'd maybe give it a good mulch as well, in that more vigour may encourage woundwood to start to close the split with complete annual rings. (which is the long term objective)

[JonnyVine]

Hi James

Odd looking tree, use two 12mm rods inserted at about 20 degrees to each other to prevent a crack developing between the bolt holes, personaly, I would not bother with nylocks as these are only necessary on rotating devices, spend the money on having oversized washers made and yes, sink them into the stem, but don't go mad.

 

You could put a restraint in the form of a strap higher up to prevent shock loading on the bolts.

[treeseer]

Using two 12mm rods down in the worst of the decay below the rubbing spot seems likely to spread decay--liquidambar fair at best w codit. 8 mm cables would do the job. but the question remains, why install hardware where woood is weakest?

 

inserted at about 20 degrees to each other to prevent a crack developing between the bolt holes is a good idea.

 

sinking washers into the wood would be highly likely to spread decay and risk failure of the support system. forbidden in A300

 

A300 calls for a cable--could be a dynamic strap-- higher up to prevent shock loading on the bolts.

 

The pruning job is nice and symmetrical, but more may need to come off that rotten stem