A Prop too Small -- and a Bridge too Far

[TreeGuyHR]

Did an assessment of this Catalpa (not sure if it is Northern or Southern, no flowers or "beans" to examine). I estimated the weight of the side-trunk (sub-trunk, what have you) at about 2,416 lbs. (in leaf). It was 14 ft. to a prop a short distance from where it forked to an 8 and a 9 in diameter limb (35 ft. total length as projected on ground); it was 27 in. diameter 2 ft. out from the trunk and 18 in. diameter at the prop just before the fork. Some decay here and there in the sub-trunk, a large open hollow in the main trunk near the attachment, and a small hollow in the "branch collar". The owner had installed the prop some years earlier: a 4x4 nailed and screwed to a pre-cast deck post footing and toe-nailed with lags to the underside of the sub-trunk.

View attachment 275711View attachment 275712View attachment 275713

I concluded that the prop was insufficient, and recommended installing a much heavier one, properly installed, as well as a Cobra flexible cable support system. I did not include a detailed description in my report, as this would take a lot more time; I would probably include that research and design cost in a bid to design, fabricate, and install it (I would sub out the metal work). These installations can be complex and expensive.

The ANSI A300 and companion BMP booklet don't say much about props, I assume because they are very site and tree specific. What you can conclude generally is that those standards say to install one that is big enough and doesn't damage the "branch" while being attached to it so the branch (or prop) won't fall off.

OTH, I have seen props described at conferences that are a saddle type without attachment; how to deal with the reaction wood that will grow around this type is an open question.

A rough idea I have for this Catalpa would be to make a prop from steel, with a yoke welded to the top. I would probably not have a central bolt screwed into the underside of the limb as both ANSI and the BMP describe, because there is some internal decay. I found it in some spots but not others using a 10 in. drill bit.

The placement of the current under-engineered prop seems to me to be too far out. I concluded this based on several diameter measurements, calculation of volume, and weight. I could go into detail on the calculations, but let's assume these numbers are accurate: the prop is at 14 ft. where the sub-trunk narrows suddenly; at this point, it is 40% out based on length, but 77% out based on volume and 71% out based on green weight, including an estimate of 200 lbs for twigs < 1 in. and leaves (visual assessment: four big armloads). Nearly all the fine twigs are beyond the prop, so the 71% is a little low.

The prop is currently in a spot without decay, but if moved closer to the trunk, would likely be under a section with decay, so the idea of drilling a large hole for a 7/8 galvanized piece of threaded rod seems like a bad idea, even though that would be "ANSI spec". I assessed decay visually and with a 10 in. 7/8 drill bit. The current prop is holding some weight, but not much, or its attachments top and bottom would probably have torn out of the 4x4. It is slightly off vertical, maybe 2 degrees max (towards the street); I should have measured that with a plum bob. The sub-trunk is pretty much centered over it side side.

Thoughts?

 

[newsawtooth]

Thoughts?

There must be some condition where young trees hide outrageous lateral limbs from arborists until they are multi-stemmed, 50' long, and 12"+ diameter. Maybe a bridge to far in light of the targets?

 

[derwoodii]

big bit of timber to hold so here some ideas by high end tree co down here Tree Propping

 

[TreeGuyHR]

big bit of timber to hold so here some ideas by high end tree co down here Tree Propping

Well, I sent them an email asking if they had a representative here. Probably they don't, and I would think it would be prohibitive to fly someone out to spec the materials, have them fabricated, shipped, then fly someone back to install the system. Looks like they might want at least two on this limb.

It's not like the tree is growing on the US Capitol grounds (and I doubt our Republican "Tea Partiers" would go for it in that case -- probably make a big deal about it for political points).

 

[derwoodii]

Well, I sent them an email asking if they had a representative here. Probably they don't, and I would think it would be prohibitive to fly someone out to spec the materials, have them fabricated, shipped, then fly someone back to install the system. Looks like they might want at least two on this limb.

It's not like the tree is growing on the US Capitol grounds (and I doubt our Republican "Tea Partiers" would go for it in that case -- probably make a big deal about it for political points).

it looks to be a public street tree, nice but maybe not worthy a few $thousand in preventative works, thou u never know. the Enspec teams a good mob & do travel they may be passing your way or may help with state side fabrication via email its only steel i beam with height adjustment on footing right sized with a cushioned cradle good a engineering shop should be able to for about 2K

anyhoo let us know how u go.

 

[treeseer]

...the idea of drilling a large hole for a 7/8 galvanized piece of threaded rod seems like a bad idea, even though that would be "ANSI spec".

:rolleyes2: not sure what this means--reference? And what is the objective here anyway?View attachment 275833

Maybe pruning is a better solution. Red cuts if limb is weak, orange cut if very weak.

View attachment 275834 Installing a prop in a public rightofway seems complicated.

 

[Pelorus]

What's the Cobra cable gonna achieve?
To keep costs down, you may want to approach a local High School welding / shop class to see if they would be interested in building the prop.

The client pays for the materials, and makes a donation to the school.
This is the route our local volunter FD took for the fabrication of a hose drying rack.

 

[TreeGuyHR]

it looks to be a public street tree, nice but maybe not worthy a few $thousand in preventative works, thou u never know. the Enspec teams a good mob & do travel they may be passing your way or may help with state side fabrication via email its only steel i beam with height adjustment on footing right sized with a cushioned cradle good a engineering shop should be able to for about 2K

anyhoo let us know how u go.

Well, I did email them. I'll let you know what they say. My impression of the homeowner is that he is willing to pay to preserve this tree, just don't know how much. It is an historic old tree (small "H", no actual designation as such).

 

[TreeGuyHR]

:rolleyes2: not sure what this means--reference? And what is the objective here anyway?View attachment 275833

Maybe pruning is a better solution. Red cuts if limb is weak, orange cut if very weak.

View attachment 275834 Installing a prop in a public rightofway seems complicated.

If you look at the ANSI A300 (Part 3-2006) it calls for "attachment" of limb to prop.The BMP booklet has some diagrams. I tend to go big with my hardware, so a piece of 7/8 rod seems like a good idea for a greater safety margin. Currently, there are two 1/4 in. diameter lag bolts toe-nailed to the bottom of the "limb"(attached at an angle through the top end of the 4x4).

Problem is, as I too-windilly said, the best place for the prop -- about halfway in based on weight, after some end weight reduction, IMHO) would likely put it in a zone with some decay. So I don't like the idea of drilling through internal containment.

The HO said categorically he did not want green wood pruned, so I did not remove any (except for a cracked limb supported on a dead one over the street). I'll make the case for a light pruning in connection with putting in a support system. I have to deal with the HO cautiously, because he initially stated he had done this or that with this and other trees on his property, and was proud of it, but few in the arborist community would agree with him (e.g., painting cuts, trying to kill advanced decay by poring a fungicide on the side of the tree).

 

[TreeGuyHR]

What's the Cobra cable gonna achieve?
To keep costs down, you may want to approach a local High School welding / shop class to see if they would be interested in building the prop.

The client pays for the materials, and makes a donation to the school.
This is the route our local volunter FD took for the fabrication of a hose drying rack.

I like your idea about having the HS across the street make a prop fro the tree in their metal shop.

The Cobra system would be extra insurance on keeping the big lateral stable. OTH, the rest of the tree is defective too, so perhaps it wouldn't really help much overall to stress the other leaders just to add some security to this one. The targets here are the highest value you run across: sidewalk and street across the street from a school.
I was considering installing cables because the prop, if closer to the trunk, would increase the load on the part of the lateral beyond the prop, perhaps making t more likely to break at or beyond the prop. Currently, it hypothetically is more likely to beak between the prop and tree.

At any rate, I am just going to propose some options, and see what the HO would like to do to reduce risk. For all I know, if his current prop was removed, the lateral wouldn't move at all. However, If I was to test that (by jacking the limb slightly , removing the prop, and letting it down slowly to see if it dips) I would be liable for putting it back to at least the condition it was in before (and I couldn't just use his old prop, because I have concluded it was insufficient). I would want to get a contract signed on replacing the prop first!

 

[Pelorus]

The Cobra system would be extra insurance on keeping the big lateral stable. OTH, the rest of the tree is defective too, so perhaps it wouldn't really help much overall to stress the other leaders just to add some security to this one. The targets here are the highest value you run across: sidewalk and street across the street from a school.
I was considering installing cables because the prop, if closer to the trunk, would increase the load on the part of the lateral beyond the prop, perhaps making t more likely to break at or beyond the prop. Currently, it hypothetically is more likely to beak between the prop and tree.

You are proposing giving Joan Rivers a facelift, with periodic check ups, and a complete makeover in 12 years. For a client who seems to be a bit of a lunatic. If this tree were in my front yard, it would be gonzo, and new ones established to eventually take it's place. And the cycle of life would go on.
You are not going to be able to guarantee any work you do to this tree against failure, and a case could perhaps be made that your actions contributed to it's failure. The prop is one thing, but increasing dynamic forces on decayed leaders is ill-advised, imo.

 

[TreeGuyHR]

You are proposing giving Joan Rivers a facelift, with periodic check ups, and a complete makeover in 12 years. For a client who seems to be a bit of a lunatic. If this tree were in my front yard, it would be gonzo, and new ones established to eventually take it's place. And the cycle of life would go on.
You are not going to be able to guarantee any work you do to this tree against failure, and a case could perhaps be made that your actions contributed to it's failure. The prop is one thing, but increasing dynamic forces on decayed leaders is ill-advised, imo.

Good point. The guy can't even give me a date on when he put his prop under the lateral. I might incur the LEAST liability by simply replacing the prop in the same place with a beefier one. BTW, I miss-typed: I didn't test for decay with a 7/8 bit :msp_scared:, but a 1/8 :msp_biggrin:

As you know, the Cobra system is advised where there is decay to avoid putting anchors through decayed would. I have done a number of traditional cable and brace jobs, mostly for co-dominant leaders in ponderosa pine and Douglas-fir. While I did not find decay i the other leaders above the main fork (with a mallet), there is a large decay pocket in the main trunk below the forks. I suspect the decay fungus is the sulfur shelf polypore, by the HO description of it and pattern of decay. There probably is some decay traveling upward into at least the base of the leaders that I could not distinguish with a mallet strike. I drilled the main trunk, but couldn't reach the pocket, meaning the main trunk is probably moderate risk. The tree has a twisted grain, with bulging fast growing reaction wood in "coils" with loose bark over dead wood here and there. This pattern repeats out onto the leaders and even large limbs.

So, the tree is pretty complex, and you are right, the less i try to "srtabliize" it is probably for the best, liability wise.

Another couple pics:

View attachment 275916View attachment 275917View attachment 275918

The first pic is from the west side, the second of the East side, and the third from the west side again (school in background). Prevailing wind is from the west in summer

 

[derwoodii]

after more pictures tending to agree with treeseer and pelorus. That trees perhaps past worthy to spend big $ on. Prune off end weight or put it on tree palliative care regime, reduction cutting to preserve while saving $ for the replanting the next generation.

 

[TreeGuyHR]

after more pictures tending to agree with treeseer and pelorus. That trees perhaps past worthy to spend big $ on. Prune off end weight or put it on tree palliative care regime, reduction cutting to preserve while saving $ for the replanting the next generation.

It's up to the HO to decide. It is an interesting tree. Looks just like the one in "Fern Gully" with Tim Curry as the voice of the evil spirit trapped inside (acchhh -- saw it around 40 times with my son when he was small!)

https://www.google.com/search?q=fer...gLZloDACw&sqi=2&ved=0CDAQsAQ&biw=1697&bih=775

And yes, it portrayed loggers as ignorant boobs, tad unfair!

 

[treeseer]

Categorically refuses to prune green wood? And impervious to persuasion otherwise? Wha tis the city's attitude toward all this load over their rightofway?

Catalpas are way tough and that tree is full of character. But the end of the branch seems to suppress those pines, and reduction would not result in a loss of any character/historic value. my biz has a high risk tolerance but i would be very leery of any involvement in re/propping that rascal without pruning. maybe show the owner the A300/BMP language on pruning before supporting?

re A300, the hardware is re bracing so do not apply to propping. Part 3 just got revised and i do not think hardware size was added in. :msp_sleep:

 

[TreeGuyHR]

Categorically refuses to prune green wood? And impervious to persuasion otherwise? Wha tis the city's attitude toward all this load over their rightofway?

Catalpas are way tough and that tree is full of character. But the end of the branch seems to suppress those pines, and reduction would not result in a loss of any character/historic value. my biz has a high risk tolerance but i would be very leery of any involvement in re/propping that rascal without pruning. maybe show the owner the A300/BMP language on pruning before supporting?

re A300, the hardware is re bracing so do not apply to propping. Part 3 just got revised and i do not think hardware size was added in. :msp_sleep:

No, I don't think he is "impervious" just proud of his "record of care" that I need to disengage him from. He is obviously persuadable because I walked away with signed contracts from the first meeting.

I haven't talked to the city; I probably should.

As far as greenwood pruning, I would absolutely include it with any support system.

RE A300, there is a paragraph in both the ANSI booklet and BMP booklet. It does not specify the diameter of the rod, as both the booklets do in regard to bracing or cable anchor hardware. I suppose 3/8, 1/2, or 7/8 rod would all work in this application. The BMP depicts a short piece screwed into the top end of the brace and into the bottom of the lateral. It is just my bent for overbuilding to increase the safety margin that was behind my suggesting 7/8. Pun in there somewhere.:msp_rolleyes:

If I replaced the brace (same spot), the diameter of the lateral at that spot is 20 in. and sound, so it could take a 7/8. I would ramp up to a 6 x 6 , so I don't think the diameter of the hole in the post (or lateral) is significant in weakening either piece, but the larger the rod, the less likely it would bend. OK, I am sure a 1/2 in. rod wouldn't bend either. ANYTHING would be better than the two 1/4 lags toe-nailed a few inches from the end of the 4 x 4 , the situation at present. They look like they would tear out of the prop with very little lateral force; same goes for the attachment to the anchor -- looks like # 8 gauge screws and modest sized nails, again, almost at the end of the 4 x 4. I would have a metal shop custom make some hardware, set it in a poured footing, and through-bolt the 6 x 6 in two spots at right angles, maybe at 1 ft. and 18 in. above the ground.

Neither booklet says anything about the problem of interior decay in regard to the attachment of lateral to prop, or the size of the anchor either.

Another question (raised by Pylorus) regards the wisdom of replacing the brace with any system at all, but especially one that is different as far as loading the tree. The tree is highly defective throughout, so placing the brace closer to the tree, and including a cabling system as I first proposed may cause unintended consequences. Replacing the brace in the same spot is probably the best choice to reduce failure risk and limit liability to me.

Thanks everyone for the comments on this thread!

Note on my weight calculation:

In writing the final draft of my report, I re-calculated my estimate of the green weight and increased it by about 30%, to 3,316 pounds from 2,416; this was because I used a more recent source: a USFS report (Miles and Smith, 2009) available online that reported average green weight for Catalpa speciosa at 50 pounds, not the 42 pounds I had extrapolated from some other sources. Plus I inadvertently left out a small section, between the prop and the forks (6 ft. by 18 - 20 inches). I used the formula for a truncated cone to calculate weight for each piece, and then added 200 pounds for limbs below 4 in. diameter, leaves, and bark on the main section. Not that the weight of the piece is discussed in the ANSI A300 or the BMP at all, I just wanted an idea of the maximum load.

Miles, R. P. , and M. B,. Smith. 2009. Specific Gravity and Other Properties of Wood and Bark for 156 Tree species Found in North America. USDA, Forest Service, Northern Res. Station, Research Note NRS-38. 35 p.