Floating floors

[claire rendall]

Hi,
I need to build a garage floor that will float above the roots of 2 mature horse chestnuts trees. I envisage that we should be able to put piles in areas where there aren't any roots, or somehow pin a floor at the front and back of the site. I then want to build an oak frame garage over the top. Does anyone have experience of this.
I look forward to any ideas,
many thanks
Claire

 

[buckwheat_la]

Starts with local building codes. I can invision many ways to do this

 

[wssix99]

Hi Clarie, It would help if you could add your location to your profile. Finding folks with your same construction situation will align to the area you live in. I assume you are in a warmer climate, since you don't need foundations for the garage?

We worry a lot with building/paving over roots in the City since everything is so cramped for space.

In general, your big, structural roots should only extend as far as the canopy of the tree. So, if you are planning on cutting back the canopy to build the building close to it - you could have some big problems ahead. If not, then the tree may miss out on some nutrients, which it should quickly make up for by growing more roots on the other sides of the tree (if your slab is covering some of the smaller ones). The tree's interference with your slab will depend on how close you are, but you may want to cut the roots and make a root barrier if the tree is placed appropriately for it: http://www.gfc.state.ga.us/community-forests/ask-the-arborist/TreeRoots-Driveways-Sidewalks.pdf

If you plan to cut the roots, I'd do that ASAP ahead of construction. We had to do some of that for our recent construction and the problems... showed up pretty quickly. (We cut some major/large roots and the tree immediately began shedding major limbs off the top. Some of the large roots also grew back in the first spring - really fast, like some kind of alien.)

 

[Kaizen]

not a good idea. covering the roots with anything will kill/ suffocate them. even a pole barn with dirt floor will eventually cause issues to them.
as asked how big are they and what percent of the radius of the drip line are you looking to cover? I forget the percent of a tree you can cut out and have it survive. its a different story putting a building under a dying tree.

 

[pmiranda]

I'd think about how much dead tree you want falling on your garage.

 

[kbs2244]

You need a tree expert before you need a construction expert.

 

[Cyberbear]

I've read that chestnut makes for good furniture lumber, give that some thought, or use it when building the new structure, thereby keeping it still on the property.

 

[kv501]

not a good idea. covering the roots with anything will kill/ suffocate them. even a pole barn with dirt floor will eventually cause issues to them.
as asked how big are they and what percent of the radius of the drip line are you looking to cover? I forget the percent of a tree you can cut out and have it survive. its a different story putting a building under a dying tree.

Not necessarily. I've seen plenty of trees planted way to close to slabs and buildings that do just fine.

Last summer my uncle had an 80' cottonwood blow over in a storm that 10 years ago he had poured a horseshoe driveway up to and around. When it went down it actually broke and flipped over the concrete 3/4 of the way across the driveway. The root ball was easily 15' across and deep.

The tree was perfectly healthy the entire time. The winds were straightline 100+ mph (according to the NWS guy that came to town); It was right before a tornado came through the south end of his pasture maybe a quarter mile out in his field.

 

[rsanter]

Even a floating floor will become uneven over time with root growth, etc

If it was my I think I would look at drilling and installing pilings into the ground and build the garage on that

Bob

 

[Kaizen]

Not necessarily. I've seen plenty of trees planted way to close to slabs and buildings that do just fine.

Last summer my uncle had an 80' cottonwood blow over in a storm that 10 years ago he had poured a horseshoe driveway up to and around. When it went down it actually broke and flipped over the concrete 3/4 of the way across the driveway. The root ball was easily 15' across and deep.

The tree was perfectly healthy the entire time. The winds were straightline 100+ mph (according to the NWS guy that came to town); It was right before a tornado came through the south end of his pasture maybe a quarter mile out in his field.

an 80 footer probably had enough roots outside of that driveway to survive. however I bet that was a 50+ year old tree. gotta think it saw strong winds like that many times but just now uprooted? even though you see roots and it looked healthy doesn't mean it was at its peak.
I've seen trees where people put in a gravel driveway only with compaction and it killed half the roots and the tree blew over. also have seen 4 pines 5 foot diameter all blow down after a road was put in and their roots cut on one side.
not a gamble i'd take.

 

[buckwheat_la]

not a good idea. covering the roots with anything will kill/ suffocate them. even a pole barn with dirt floor will eventually cause issues to them.
as asked how big are they and what percent of the radius of the drip line are you looking to cover? I forget the percent of a tree you can cut out and have it survive. its a different story putting a building under a dying tree.

Not necessarily. I've seen plenty of trees planted way to close to slabs and buildings that do just fine.

Last summer my uncle had an 80' cottonwood blow over in a storm that 10 years ago he had poured a horseshoe driveway up to and around. When it went down it actually broke and flipped over the concrete 3/4 of the way across the driveway. The root ball was easily 15' across and deep.

The tree was perfectly healthy the entire time. The winds were straightline 100+ mph (according to the NWS guy that came to town); It was right before a tornado came through the south end of his pasture maybe a quarter mile out in his field.

an 80 footer probably had enough roots outside of that driveway to survive. however I bet that was a 50+ year old tree. gotta think it saw strong winds like that many times but just now uprooted? even though you see roots and it looked healthy doesn't mean it was at its peak.
I've seen trees where people put in a gravel driveway only with compaction and it killed half the roots and the tree blew over. also have seen 4 pines 5 foot diameter all blow down after a road was put in and their roots cut on one side.
not a gamble i'd take.

KV501, has it pretty much right on this, nutrients etc will be found by the roots wherever it needs to go. You can figure that the the roots extend out about 10% further than the top foliage of the tree. Also some root systems go deeper or stay near the surface depending on the type of tree and the type of soil. So there are lots of things to consider. If you are going to hack out roots, consider doing a pruning as well. A post building is a good idea, but again you need to check your local building codes. The cool part about a post structure, is that their will be a header around the top of it so you can really do whatever you want on the bottom. Have you considered paving stone?