canopy/root spread

[travis]

a mate asked my what my thoughts were on a monkey puzzle tree, that is planted close the house which he has bought.

i think his concern was, were the roots going to interfere with his underground services etc and foundations of his building.

 

so my question is, does the root spread correlated with the canopy or branch spread. like on other species.

 

or do all trees grow differently in different situations.?

 

If it's brown, cut it down.

 

travis

[travis]

oh man, no one understands what i mean..

do the roots reach out horizontally as far as the branches do ?

i know some species send out roots far beyond the branch tips.

[Paul Barton]

Depends alot on the soil and species of tree. Some trees will send out roots radially over twice the height of the tree.

 

If he is that worried you could dig some trial pits and see if you can find any roots.

[Yorkshireman]

if its for protection RPa is 12 * dbh

[Paul Jenks]

If the house is well built and not on a highly plastic soil and the tree itself is a reasonable distance from the house it should be ok. In Chile these trees are mahoosif so it does need to be a good bit away from the house.

 

They are horrible to reduce and not much nicer dismantling.

 

How far is it from the house and how tall is it?

[travis]

re. protection RPa is 12 * dbh

 

what is protection RPa ? and what would i gain if i multiplied depth breadth and height by 12 ?

[Paul Jenks]

RPA is the root protection area as decided by the BS5837:2005. Multiply by 12 the diameter of the tree trunk at 1.5m above ground level. Then use this measurement to draw a big circle, centred on the tree, around the tree. This gives a supposedly sacrosanct area into which no construction traffic or materials or works can enter without arboricultural supervision.

That having been said a tree will often grow in a smaller area quite happily.

[Ben90]

So is it roughly 6 'stem diameters' from the edge of the stem to the edge of the RPA? Making 12 all the way across?

[Paul Jenks]

Sorry, should have been clearer. This measurement forms the radius of the root protection area. So it's 24 across the diameter.

[Ben90]

Great. I've read BS5837 but it had the proper area equation. Obviously you can't get a rough idea from that without sitting down and doing it properly, anyway the equation off the top of my head is RPA (in meters squared) = (DBH x 12 / 1000)squared x Pi

 

This gives you the area for the RPA circle, which allows you to deform one side of the circle by no more than 20% of the radius, but keep the overall area the same. A bit like squeezing a plastic cup slightly so the top forms an oval, the shape changes but the area stays the same.

 

Anyway that's the industry regulated root protection area. Of course roots grow beyond this almost always, but the damage caused outside of the crucial RPA is considered 'non-significant'.

 

If we wanted to be really strict about it you probably shouldn't even dig a hole 30 meters from a tree because you'll affect it by disturbing beneficial mycorrhizal activity!

Edited July 8, 2010 by Ben90