Foundations near mature trees 1

[Vinny7]

Hi All,

I have a building to design (large dwelling) near mature trees. The trees would be about 5-10 metres from the new building. I know a piled foundation would work but would also like to know if a raft could be used or if deep strip with compressible formwork to the sides would work. In the case of rafts or deep strips are there any special issues i should be aware of. The ground conditions are good. Thanks for any help.

Vinny

 

[fattdad]

Some of this may have to do with the type of tree. Some trees have shallow roots and others have deep roots. It's almost like guessing at this point what the foundation of the tree may be. . . . .

f-d


¡papá gordo ain’t no madre flaca!

 

[Vinny7]

I think the trees will have relatively deep roots. 4-5metres

 

[civilperson]

Any foundation or excavation within the "drip line", (the extant of the branches and leaves), will also effect the root system. If less than 20% of the "drip area" is disturbed, the tree has a good survival chance. Protect the soil from machinery compaction by use of a snow fence and DO NOT FILL on the root area without placing a 6" granular lift for air and water access to the old surface.

 

[cvg]

if you are in clay soils, the tree may be taking significant moisture out of the soil. If the tree dies, your clay soil moisture could increase, causing it to swell. Will that affect your building foundation?

 

[BigH]

Classic paper by Bozozuk on effects of trees on foundations (can search him. It is part of a NRC publication). Tomlinson's foundation design and constrution book also discusses in detail. This has been a major problem in clayey soils where moisture migration (seasonal) is significant.

 

[BigH]

http://irc.nrc-cnrc.gc.ca/pubs/cbd/cbd184_e.html

http://www.lga.sa.gov.au/webdata/re...ban_Environment_-_2005_Report_-_Section_1.pdf

http://www.golder.com/Archive/AssessingConstruction.pdf

 

[csd72]

I would suggest a root barrier to minimise future root damage.

 

[oldestguy]

Tree type also is important. Elms are bad for grabbing moisture and causing shrinkage of clays.

Sometimes it is necessary to remove the trees to avoid these problems to begin witn.

 

[csd72]

If you do remove the trees, i would recommend you remove it as soon as possible (send a letter to the client recommending this) it means that the soil has some time to 'rebound' before the foundation is built.