Palm Trees and Retaining Wall

[Haring2]

Hi Everyone…

Very happy to find this forum. We are about to jointly construct (and pay ) for 35 feet of a 4-foot tall retaining wall (estimates in at ~$40k!). The wall is retaining approximately 3 feet of the neighbor’s soil in a planter. The planter has a mix of stragglers, but most concerning king palms they’d like to keep. On the other side of the palms is a pool they are rebuilding.

The neighbor’s pool contractor said the palms would probably never grow big enough to compromise the wall in the next 40 years with the disclaimer that he’s not an arborist. The way is approximately 50 years old. We’re not sure if they’re putting the house on the market after this.

Before we share in the cost of a $40k wall, do these palm trees pose a problem for the wall and pool?

Many thanks.

 

[TheJollyLogger]

Where exactly is the wall going? Just looking at the pictures my main concern would be the damage done to the palms from the pool excavation and construction.... definitely tight quarters...

 

[Section VIII]

It's difficult to see from your photos where the actual retaining wall is planned to go. I'm assuming it's at the foreground in the last photo.

As a general rule, it's not recommended to have any vegetation within a certain distance of any structures including retaining walls and pools. Palms don't usually have an invasive root system so they may be okay...but they add weight which adds pressure in all directions (not to mention the pool). Supposedly, king palms can grow to 40 - 70 feet tall.

As long as the contractor is going to put in anchors (tie-back, deadman) in addition to rebar in the retaining wall, I imagine it'd be fine. For the price you're paying, they need to do it right (drainage, weep holes, etc...).

I'm not a contractor but I used to be a master home inspector which included inspecting retaining walls. Take it for what it's worth.

Personally, those palms are way too close to the structures and if it were my property, I'd get rid of them.

 

[Haring2]

Where exactly is the wall going? Just looking at the pictures my main concern would be the damage done to the palms from the pool excavation and construction.... definitely tight quarters...

Thanks for your reply JollyLogger. The wooden fence is on top of the existing retaining wall. Anywhere you see a wooden fence, the retaining wall is underneath. Unfortunately, the wall cracked in several places where they drilled in supports for the fence on top (not approved by us).

The last two pictures show the trunks of the palm trees about 2 feet from the retaining wall with the fence on top.

The pool belongs to the neighbors and they seem to be comfortable with the risk of both excavation of the dirt and taking down the wall for the rebuild. The pool contractor told them the trees would likely not breach the pool in the next 30 years, though is not an arborist.

Did I answer the question?

 

[Haring2]

It's difficult to see from your photos where the actual retaining wall is planned to go. I'm assuming it's at the foreground in the last photo.

As a general rule, it's not recommended to have any vegetation within a certain distance of any structures including retaining walls and pools. Palms don't usually have an invasive root system so they may be okay...but they add weight which adds pressure in all directions (not to mention the pool). Supposedly, king palms can grow to 40 - 70 feet tall.

As long as the contractor is going to put in anchors (tie-back, deadman) in addition to rebar in the retaining wall, I imagine it'd be fine. For the price you're paying, they need to do it right (drainage, weep holes, etc...).

I'm not a contractor but I used to be a master home inspector which included inspecting retaining walls. Take it for what it's worth.

Personally, those palms are way too close to the structures and if it were my property, I'd get rid of them.

Thank you, Section VIII.

In addition to growing over 40 feet tall, apparently king palms can also spread 10-15 feet. The planter created by the retaining wall is only 3 1/2 feet wide. On one website, I read they are relatively fast growers.

Drainage and weep holes are part of the plan. Thank you for the tip regarding the anchors. They are proposing to use #5 rebar which seemed a bit overkill for this project, but the pool contractor argued the 35 feet is not much wall, so the cost is de minimus. I wonder if he just has a lot of #5.

Unfortunately, the neighbors are very married to the palms as they‘re going for a tropical aesthetic in their backyard.

May I ask you in your experience as a Master Inspector if some of the cracks may have been caused by the installation of the fence brackets on the wall? The cracks were not there prior to the installation of the fence top. And would those cracks contribute to the wall failure?

This might also give you a better view of the wall that is being replaced from the other side.

 

[Section VIII]

Thank you, Section VIII.

In addition to growing over 40 feet tall, apparently king palms can also spread 10-15 feet. The planter created by the retaining wall is only 3 1/2 feet wide. On one website, I read they are relatively fast growers.

Drainage and weep holes are part of the plan. Thank you for the tip regarding the anchors. They are proposing to use #5 rebar which seemed a bit overkill for this project, but the pool contractor argued the 35 feet is not much wall, so the cost is de minimus. I wonder if he just has a lot of #5.

Unfortunately, the neighbors are very married to the palms as they‘re going for a tropical aesthetic in their backyard.

May I ask you in your experience as a Master Inspector if some of the cracks may have been caused by the installation of the fence brackets on the wall? The cracks were not there prior to the installation of the fence top. And would those cracks contribute to the wall failure?

This might also give you a better view of the wall that is being replaced from the other side.

I do not consider 35 feet to be a small retaining wall. It's difficult to tell if the fence posts caused the cracks and wouldn't have a good idea until demolition. The bracket screws/bolts don't usually extend all the way down the wall and are usually only a few inches deep. I doubt the fence post brackets caused the cracks.

It doesn't look like the old retaining wall had any weep holes. Given that the planter is only 3 1/2 feet wide, the king palm roots have a confined space to spread. This also means that tie-backs and deadman (installed somewhat horizontally) would be difficult to install according to recommended "holding" depths. These are different from the rebar anchors in the retaining wall itself.

Palm roots don't generally go very deep (12" - 36" according to some sources) which would mean that most of the weight of the root "ball" and palms themselves would be pushing against the top 2/3 section of the retaining wall. This logically would make it "top-heavy". Add to that any hydrostatic pressure in the planter against the retaining wall.

I agree with TheJollyLogger in that there's a good potential for demolition/excavation to damage the palm root system. My bigger concern would be that the palms and soil that the old retaining wall is holding would all fall over/out during the demolition and/or excavation. Finally, the tree in your second picture has exposed roots near the surface and is too close to the retaining wall. Soil displacement by that tree's roots may have contributed to the cracks in the retaining wall. Once again, it's difficult to tell if the old retaining wall had any type of footing under it.

Now I see why the quote was so much. If the retaining wall replacement is a must, I personally would remove the palms (or relocate away from the wall?) and the tree with exposed roots. Retaining wall replacement would make it much easier to properly complete with those gone.

Disclaimer: Home Inspectors can only inspect what they can see or access without damaging anything. I am not trying to second guess any of the contractors.

 

[Section VIII]

One more thing:

I don't want to alarm you but the cracks in the current retaining wall will probably get larger with time without intervention.

 

[TheJollyLogger]

I would rate the odds of removing that wall and replacing it, and those trees surviving it extremely low.

 

[Aknutter]

I would rate the odds of removing that wall and replacing it, and those trees surviving it extremely low.

Especially if a footing is dug up to support the wall

 

[NYresq]

I cant speak about retaining walls, but I have some experience with palm trees. First and foremost, palm trees are HEAVY!!!! They are heavier than concrete of the same size. Its deceptively heavy. They are filled with water when alive. And did I mention they are heavy? If anything cuts or breaks the roots on a side, they are susceptible to leaning and way more chance of being blown over in a good wind. Once they start to lean, it breaks more of the roots below the surface and gets worse as time goes on until they fall over.

And they dont have a wide reaching root system, so the support system is not like an oak tree or something with a wide and deep root system.

As mentioned above, I'd be surprised if they can remove and replace a retaining wall close to the trees without doing damage.

oh, and they are heavy... like molten lead kinda heavy. Once it dries out, its probably 1/4 the weight of the stuff when its first cut.

 

[Haring2]

I cant speak about retaining walls, but I have some experience with palm trees. First and foremost, palm trees are HEAVY!!!! They are heavier than concrete of the same size. Its deceptively heavy. They are filled with water when alive. And did I mention they are heavy? If anything cuts or breaks the roots on a side, they are susceptible to leaning and way more chance of being blown over in a good wind. Once they start to lean, it breaks more of the roots below the surface and gets worse as time goes on until they fall over.

And they dont have a wide reaching root system, so the support system is not like an oak tree or something with a wide and deep root system.

As mentioned above, I'd be surprised if they can remove and replace a retaining wall close to the trees without doing damage.

oh, and they are heavy... like molten lead kinda heavy. Once it dries out, its probably 1/4 the weight of the stuff when its first cut.

But are they heavy?