Giant Sequoia and shed/shop foundation design

[giantsequoia]

Hi All,

Hoping to get some insight on my plans to build near a giant sequoia in the rear of our yard.

The tree is 5 ft dbh and has a 40' dripline diameter. it is not very tall, about 70', or so.

I'd like to put in a shop, storage shed on our city lot. My plan is to do a pier and beam foundation with one corner of the building being 9-10 ft from the tree trunk. the next closest piers will be 20,' right near the edge of the dripline.

Any thoughts on tree impact, both from a health of the tree standpoint and an impact to the piers over the long term (10-20 years?).

The building is 400 sq ft, with only 100sq ft being under the dripline. Would I be better off with a slab foundation? i don't need to excavate this way, just a slightly thickened edge. Not sure if this will be worse for the tree given lack of moisture and oxygen and if the slab will just heave over the years as the tree grows?

What would you do to both preserve the tree and have a building that will last?
Thank you

 

[jetsam]

If you're pouring piers anyway, consider skipping the slab and keeping the floor a few inches off the ground (for example, lay 4x4 or 6x6 joists directly on a bed of gravel, level them out, then pour the piers flush with the ground so you can bolt the joists that hit them directly on.).

You may need a little ramp to drive equipment up and down, but it's going to be more forgiving of root movement over the years than a slab will. You won't have to worry about the wind picking it up if you anchor it to the piers.

I'd also look into roofing that is tolerant of perpetual shade- Palram or corregated metal, maybe.

From a tree standpoint, I'm no arborist, but I imagine the tree would appreciate it if you built somewhere else!

 

[Marine5068]

As a building designer, I like what Jet said.
You really should try to build it away from the tree if you can.
But if not, then piers will be better.
Maybe you can reduce the area of the needed concrete pad to one side away from the roots and plan the building accordingly, if you even really need a pad.
I built a large shed attached to a car port with gravel floor for my lawn tractor, snow blower and wood splitter with only pier footings.