Hi Everyone! Is there any factual info out on root barriers in regards to them helping to stop trees from absorbing water from underneath a foundation? It seems to really accomplish that you would have to trench around the side of a house and install a barrier about 10 feet down and seal off the area which wouldn't seem very wise or cost effective since this particular soil is clay. On the side of the house that has gone down there are 3 20" DBH oaks that the trunks are 21 feet away from the foundation and the limbs spread an additional 15 ft or so over the top of the house. The engineers recommend installing root barriers, I just don't see how this can help or be a cure all. Thanks Ken

Reply to post by Ken Six, on May 06, 1999 at 23:14:04:

Sounds interesting. In theory I don't know why it would not work. I've read or been told that there is literature which indicates the density of a barrier that roots will not penetrate. Reportedly the barrier alone may be sufficient w/out impregneted herbicides as in BioBarrier (TM).

I'd think the biggest problem would be getting the barrier installed 10' down (that's a big ditch cut back to angle of repose) and uniformly backfilled with no punctures or tears.

Hmmmm. Maybe something rigid. Aluminum plate. Fiberglass, like a boat. Doesn't 3M or GAF or somebody make 4x8 corrugated fiberglass panels for roofing sheds and greenhouses and things like that. Sort of translucent green.

Are there trenchers or root cutters that can get you down 10' with the working room you have?

Reply to post by Scott Cullen, on May 06, 1999 at 23:14:04:

Scott, thats exactly my point! The engineers around here are recommending instalation of root barriers (without any specifications). So the tree service's will go down and install a root barrier (2 sizes 12" or 19.5")made by the Deep Root Corp. or make there own. Sometimes out of plexiglass @ 3ft deep. My question is how can a root barrier @ 2-3ft deep have an impact on the trees absorbing water from under the foundation? How can this help a house not to settle if the soil is clay? It seems as though the house weighing tons on a 12" or so foundation would act as some sort of barrier unless ther was something there for the roots underneath it. Won't the trees along with the shrubs & grass be drawing water from the area anyway. Ken

Reply to post by Ken Six, on May 07, 1999 at 06:52:44:

My knowledge of subsidence is limited mostly to the discussions here and reading a few technical articles. As I understand it, the problem is shallow foundations - especially slab on grade types - over expansive clays. These soils expand when wet, shrink when dry. Apparently, tree roots can exacerbate the drying, leading to shrinkage and subsidence. I can only guess that the engineers are speccing 10' deep barriers because the roots might go under a shallower one seeking moisture or that they simply want to insure no tree related moisture loss to that depth. I suppose the soil could wick moisture upward to shallow roots. I guess it comes down to the expense that's bearable to keep the trees.

Reply to post by Scott, on May 07, 1999 at 07:23:51:

Th engineers have no specs, I was thinking that to do anything permanent you would have to trench down 8-10 feet which to me and I could be wrong would be kind of ridiculous. I guess also I am not really sold on root barriers in this type of situation. Ken

Reply to post by Ken Six, on May 07, 1999 at 17:41:02:

If you don't go deep enough, you run the risk of not keeping the roots out for a long period. If the barrier is intended near a foundation, there is probably oxygen available at more than normal depth- either by diffusing through walls, or by diffusing through the looser soil near the foundation. The act of trenching for the barrier will itself introduce an avenue for gas diffusion. The whole idea is to keep the roots away from the foundation a sufficient distance that they will not shrink the soils by drying them.

Reply to post by Russ Carlson, on May 07, 1999 at 18:03:02:

At the risk of repeating myself;

The problem is not the tree, but the engineering, Here in s/e WI the good contractors put the foundation on less dynamic soil thatn the native clay, then backfill around the basement with the same or gravel. There's a big industry in basement repair where they trench around the house, straighten/waterproof the basement walls and backfill with gravel (my folks got 14K worth about 15 years ago, even with a Honey Locust 10ft from the foundation).