Plants do not make any kind of effective sound barrier....unless you have a very deep and dense planting of them....like several hundred feet. You need a solid surface - a masonry wall - to deflect sound.

As to the roots harming the retaining wall, it is certainly possible. We have no idea how the wall was constructed and if in good repair and any tree that grows rapidly to 60+ feet is going to produce a massive root system as well.

The cinderblock retaining wall will be brand new and I'll plant the trees as close together as possible. Other tree/shrub suggestions are welcome.

I sure wouldn't use Leyland cypress! They are just too darn big for this application....and for most residential properties unless you have a lot of acreage.

As we have no idea where you are located in order to make any specific suggestions, you could plant whatever you like that fits the space and offers whatever other attributes you are looking for. You just need to understand that plants DO NOT WORK as any kind of effective sound barrier.

Yes: roads passing through wooded areas can be easily heard a long distance away. Unless your cinder block wall is somehow engineered to hold up against it the growth of the tree roots will probably push it over eventually - if you plant something as large growing as Leyland cypress.

I think we need to see the space and also understand where the noise is in relation to your home.

There is a certain proximity of the barrier as it relates to the sound and it’s effectiveness.

If you have a freeway that is 1/4 mile away yes the barrier won’t do anything. If the source is from the street you’re on it certainly will block some of the sound

"it certainly will block some of the sound"

Not enough to make an appreciable difference. But you may realize some benefit just by virtue of the property being raised above street level........and the existence of the retaining wall.

To deflect or reduce noise, you need a solid surface - solid masonry, earth, even a closely paneled wooden fence (although much less efficient). Plants are not solid and sound waves will move right through them. You will receive some privacy via this type of planting but it will do bupkis for sound deflection or absorption.

A 40’H row of too closely planted trees there isn’t the solution.

We need some more info and pictures

Patricia, I am not sure we do in order to answer the question :-) Plants are ineffective in reducing or deflecting sound and something as massively and as fast growing as a Leyland cypress could easily compromise a block retaining wall, not to mention dwarf and uncomfortably enclose a front garden.

But if the OP needs or wants other possible solutions, then a photo or two and more info might be warranted.

cinder blocks are not used for retaining walls .... you seem to be using the words interchangeably .... could you show us an example of the blocks...

and also the size of the block ?? ... ive seen them as small as home owner project of say 8 by 12 inches .... to a couple feet large ....

i dont recall where you are .... whats the native soil ...

and how are they being installed?? .. professionally with all the proper foundations and soils behind???

and how far from the wall are the trees being planted from the stone work???

i also think the leylands have too much potential for the application

https://duckduckgo.com/?q=Leyland+cypress&t=ffcm&ia=images&iax=images

ken

Yes we do need info and pictures there is no other way to even begin to suggest options.

"cinder blocks are not used for retaining walls"

Not sure where that idea comes from!! Cinder blocks, aka CMU's, are commonly used for retaining walls. You can find photos and DIY instructions all over the 'net.

I'll agree w/GG that it won't significantly block sound. As an old engineer understanding acoustics, it would block higher-frequency sounds alittle, but not lower-frequency sounds.

Since it is pretty firmly established that plants alone will not block or deflect sound to any significant degree, other than a taller, solid wall or a pretty solid fence, not sure what other options you think are available. The OP is free to plant whatever she likes on the top of the wall for greenery or privacy screening as desired but plant material is not gonna stop noise!

I don't have pictures because construction won't be starting until spring next year. Here's the story:

The city is widening the street in front of my house. The two lane street will be 6 lanes next year. My lot is elevated from the street by about 6 to 10 feet, so part of the things I asked for in my contract was to have a retaining wall when the cut off the front of my property.

Right now, with two lanes, the plus 65 mph traffic is so loud that you can't hear to talk to anyone if you're standing outside. I can only imagine what it's going to be like with six lanes. So that's why I was thinking about a tree line to help mute the sound, and my friend Google was the one who suggested the cypress trees.

I don't know what material the city's contractor will use to build the retaining wall, but I imagine it will be cement of some sort, and as I've seen the retaining walls on the freeways and in front of subdivisions, it appeared to my untrained eyes to be cinder blocks?????

So my question here on the forum was in the planning stages. I don't know what to plant, and whatever I do end up planting, I certainly don't want to have it wreck the newly placed retaining wall. Just trying to think ahead.

The retaining wall that will be built should be very high quality, not cinderblock, and should block ground level view. You should be able to find out exactly what you are getting for a wall, then go from there.

That really sucks, and we can appreciate your problem much better. How far away will the street be from your home? In other words, how many feet deep will your yard be when they're done?

Are they building a retaining wall or sound barrier? The latter is what you need and should be bargaining for. It's what you see when you drive along a highway and there is a big wall that blocks you from seeing a subdivision. They are often concrete, but can be stone or other materials.

Once a sound barrier is built (which could also serve as a retaining wall), you can then plant something appropriate for your site and zone.

All I know at present is that they will be needing 10' of my property behind the wall for their construction, and the wall on my side will extend underground in the shape of one side of a pyramid (I don't know if I've explained that properly.

Sounds like a typical concrete retaining wall with footer. Since this is being designed, engineered and constructed by the city or local DOT. it should be able to tolerate normal root pressure. But since as of yet you have no idea how tall this wall may be and how it may appear on your side of the property, it's a bit premature to suggest any plantings or their placement.

Interior noise can be virtually eliminated but, it will require a de-coupled interior wall and new triple glazed windows. Seek guidance from an Architectural design / build firm. In future pay attention to any "easements" shown on the master plan at City Hall as easements (esp. on main roads) are common.

If construction hasn’t begun, maybe sell the house and move before it does. You are right that it will only get worse. With no appreciable remedy other than a thick massive masonry wall. And it would need to be all the way around the house, and taller than the house, to effective block the type of noise that you’re talking about. Think freeway sound baffle barrier walls, but just around your house. Otherwise you get flanking sounds penetrating and reflective sounds bouncing off of more distant objects back into the house from other directions.

6 lanes and 65+ mph speeds sounds like they are planning a freeway for your doorstep!! How will you navigate your comings and goings in and out of your property with that kind of traffic?

I'd consider moving as well if that is the prospect........

I know, huh. I'd love to be able to see the environmental impact study shown to the city for this project. Yes, it is rural, but there are houses along the route, and we're not that far off the street (about 75' for my house)

I'm 82, and I don't plan on trying to find another house in my lifetime.

Is there a reason you can't access the environmental impact study? Aren't all the planning documents public access?

If you’re 82, then I’d seriously think about delivery of life necessities by Amazon drone, and make the city build that castle wall around the house. And I’d never venture out again. You’d need a turn around space for visitors up at the house, if you wanted visitors instead of just Skype visits. But there’s no way Id ever want to pull out of a severe downhill driveway like that and out into freeway traffic.

Or sell it and buy into a trailer home park in FL.

I fight billboards but in this case I am actually going to recommend you get one or a few installed as barriers and to compensate you for your loss!

Sound is not the only issue. The air pollution will be terrible. I once lived next to a tollway and was NEVER able to open a window or sit on my porch. I had to move.

Environmental impact study? Not needed when widening an existing roadway. In an urban area (Phoenix AZ) homeowners sued to make the City buy their homes because of the impact. The settlement took a decade. Unsolicited advice; sell it now for whatever you can get and enjoy the rest of your life elsewhere. I have great sympathy for you.

The aforementioned high concrete walls like I see being built - by involved public agencies rather than individual property owners - between residential neighborhoods and freeways here are the kind of thing you would need to cut the traffic noise to any appreciable degree.

And I've noticed that even with the ones in my area passing vehicles can still be heard while standing near the wall, just well overhead instead of down lower. So probably anywhere an adjacent building sticks up above wall height there is little relief at that level.

Like I said, there is about 75' from my house to the property line at the street. And about the retaining wall - it won't be any higher on my side than the ground. The city will be cutting off my elevated lot and I've asked for a retaining wall to protect the raw cut. They will have to replace my front fence, which is now a 4' redwood fence, and I've asked if that could be replaced with a 6' block fence, and they're thinking about it. They're not sure they want that 'look' on the street side, that is, 6' of retaining wall then 4 or 6 more feet of privacy fence. Whatever they decide, I WILL have my privacy fence!

My lot is about 6' higher than the street. I want to plant a row of Leyland cypress across the front to act as a sound barier

Like I said, there is about 75' from my house to the property line at the street

Whatever they decide, I WILL have my privacy fence!

What is the relationship between these statements? First you talked about cutting noise, then you appear to be saying the street is too far away for noise to be a problem. And finally that all you are concerned about is blocking the view.

You misunderstand. Quite a few posts back someone asked how far my house was from the street. So I said it was 75', not that it was too far. Everything I previously said about noise is true. One can't hear each others' conversation when standing outside. And a privacy fence isn't for blocking the view. My whole lot has a privacy fence around it to keep the animals in and people out. When the city cuts off the front of my property, which includes my fence, they are obligated to put another fence back up on the property line. Has nothing at all to do with a view. I want the trees inside my fence to mute the traffic noise and the whole object of this thread was to know if the trees would harm the new retaining wall.

Sheesh!

I think was can close this conversation now. I have received the information I asked for.

No plant will absorb all much in the way of sound but any green wall that keeps its leaves year round would provide some privacy -- that would be a good objective.

Since your lot is already 6' above the sidewalk/road level, you would only need a shrub that grows 4' high to have a 10' visual barrier.

You could stagger two rows of shrubs to make your green fence more dense -- planting one row with the recommended distance between them and then a second row, placing the shrubs in that row so they serve as a visual block of the space between the shrubs in the first row. That spacing would also provide more root room and decrease the likelihood that the roots would eventually negatively impact your wall.

From what I know (and I'm not a pro):

I've read you should feet a tree beneath the outer edges of its limbs because the larger roots of trees tend to grow the diameter the foliage on the tree grows and the tree feeds there even if the roots extend farther ... so, logically, if you choose trees with most limbs extending about ten feet out from the trunk, you could probably plant them ten feet from the wall with little, if any, issue with roots damaging the wall -- at least not any time soon.

There are some trees that have deep tap roots and some trees that don't but have a lot of roots closer to the surface. See which kind of root the trees you are actually considering have and choose accordingly.

You might consider a combination of trees and shrubs. None smell better than a gardenia in bloom.

Good luck in your efforts.

This is just an observation, any time that a city or state plans to increase traffic by that amount not only is a solid barrier above grade needed for sound but also safety, to keep people and pets and wild life from crossing that much traffic. I don't buy a planners idea that they would HAVE TO THINK ABOUT a barrier above grade. I would sue them if they refused. There must be more people affected by this is there not? I would get in contact with someone that is directly involved with the project otherwise you will just get a runaround. Probably something that you do not wish to do but I say RAISE A LITTLE HELL.