Installing driveway near old trees (2024)

I have an old japanese maple and dogwood about 3 feet from my driveway. the driveway is not paved and is only a 8' wide strip of grass with two ruts from infrequent parking of cars. I want to install a more useful driveway here using porous pavers (e.g., Eco-grid, Turfstone) to maintain drainage and a rustic look and prevent the muddy ruts.

I will have to dig away the topsoil in the grass driveway to install a 10-18" base of stone for a solid base for the pavers. Some of the tree roots will become exposed in this process. Can I re-bury the roots in crushed gravel? Will this stone damage the tree roots by abrading them, or changing soil pH? How best to proceed?

If you have any other suggestions that will allow me to keep these trees healthy and happy, but still result in my getting a usable (hard-surface) driveway, i'm all ears!

thanks in advance,
Bob.

campag said:

I will have to dig away the topsoil in the grass driveway to install a 10-18" base of stone for a solid base for the pavers.

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Who told you this?

Solid base can be achieved without digging. Best to level with structural soil then lay down geotextile then your stone. Basic operation.

Driveways should go above, not through, roots. Japmaple would freak out totally if treated as you suggest.

Granted, digging to depth for the base is going to be hard on the trees.

On the other hand, inadequate base will cause your pavers to shift and settle. 10"-18" is way too much for a driveway. You could support regular semi-truck traffic on that kind of base.

6" base layer done in "crusher run" or "AB-3" will be more than enough for your car traffic.

A common error when installing pavers is to dig the hole, add the AB3. then screed it out and lay the brick. Nope! You need to run a vibratory compactor over the soil, then add a 3" layer of base, compact it, add more base (in 3" "drifts"), until you are as deep as you planned. Never use more than 1" of sand for the final screed: it will shift and settle under heavy loads.

I am not familiar with "porous bricks". If they are 50% hole, and 50% concrete, they will likely settle no matter what you do.

It goes without saying that your trees will not like all that compaction, either. It will certainly compromise their health; so you will need to choose between a great driveway or healthy trees.

pdqdl said:

You need to run a vibratory compactor over the soil, then add a 3" layer of base, compact it, add more base (in 3" "drifts"), until you are as deep as you planned. .. It goes without saying that your trees will not like all that compaction, either. It will certainly compromise their health; so you will need to choose between a great driveway or healthy trees.

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Usually true, but using expanded aggregate in the sub sub base/structural soil allows for root expansion and gas exchange and water movement. Yes compact as you go, but you do not have to dig.

Of course, a picture would help a lot here.

Guy, I know better than to argue with you about the best care for the tree, but you should be very careful about branching out into landscaping.

Expanded aggregate (say...3/4" clean gravel) will end up being a nightmare. While it works great for putting under highways and parking lots, there is no way to screed it out real smooth to get the pavers level. Attempts to overcome that problem will make it worse, because any finer material will settle into the pores and allow rampant settling of the pavers.

Perhaps a compromise would be to use a really well made textile fabric laid over the expanded aggregate as a barrier against finer materials, followed with a thin layer of sand for final screeding.

I presume that these "porous" pavers consist of large holes, or are they simply porous enough to allow water to pass through? If large holes, they will still settle in sand, unless filled to the top with sand/soil to spread out the pressure from the tires.