"Earnest Trawler" wrote in message ...
[...]
If this one breaks the drain then it will have to go too. A bill to fix the
drain would be annoying but not a disaster, so it is a risk I am willing to
take, the drain would go long before the roots got to the house foundations.
[...]

I'd love to hear from a structural engineer or similar authority on
this question of tree-roots and house foundations. I imagine, quite
likely wrongly, that modern concrete footings must be too tough a nut
for the roots actually to damage. But would a really vigorous root
system, in time, alter the subsoil conditions so that prolonged
passages of extreme weather (or over-extraction from the water-table)
could result in subsidence even with modern building practices?

On the other hand, old country houses in some places may hardly have
foundations at all: I had a Welsh farmhouse which seemed to be
balanced on no more than a few strategically-placed big stones on
boulder clay. It was remarkably sound; but I could easily guess at the
damage a good weeping willow might have done.

Drains are a different story, of course.

Mike.

The message
from (Mike Lyle) contains these words:

I'd love to hear from a structural engineer or similar authority on
this question of tree-roots and house foundations. I imagine, quite
likely wrongly, that modern concrete footings must be too tough a nut
for the roots actually to damage. But would a really vigorous root
system, in time, alter the subsoil conditions so that prolonged
passages of extreme weather (or over-extraction from the water-table)
could result in subsidence even with modern building practices?

Don't you believe it. The roots grow and in effect, use hydraulic power
to do so. Have you never seen a mushroom pushing up through a tarmac
pavement? They will even lift paving stones.

On the other hand, old country houses in some places may hardly have
foundations at all: I had a Welsh farmhouse which seemed to be
balanced on no more than a few strategically-placed big stones on
boulder clay. It was remarkably sound; but I could easily guess at the
damage a good weeping willow might have done.

My parents' house was built on a foundation of willow twigs, probably
more than four hundred years ago.

Drains are a different story, of course.

No, just a different chapter of the same story.

--
Rusty http://www.users.zetnet.co.uk/hi-fi/tqt.htm
horrid·squeak snailything zetnet·co·uk exchange d.p. with p to
reply.

"Rusty Hinge" wrote in message
...
The message
from (Mike Lyle) contains these words:

I'd love to hear from a structural engineer or similar authority on
this question of tree-roots and house foundations. I imagine, quite
likely wrongly, that modern concrete footings must be too tough a nut
for the roots actually to damage. But would a really vigorous root
system, in time, alter the subsoil conditions so that prolonged
passages of extreme weather (or over-extraction from the water-table)
could result in subsidence even with modern building practices?

Don't you believe it. The roots grow and in effect, use hydraulic power
to do so. Have you never seen a mushroom pushing up through a tarmac
pavement? They will even lift paving stones.

On the other hand, old country houses in some places may hardly have
foundations at all: I had a Welsh farmhouse which seemed to be
balanced on no more than a few strategically-placed big stones on
boulder clay. It was remarkably sound; but I could easily guess at the
damage a good weeping willow might have done.

My parents' house was built on a foundation of willow twigs, probably
more than four hundred years ago.

Almost ditto Chichester Cathedral. It floats on wood on a bog.

Drains are a different story, of course.

No, just a different chapter of the same story.

Franz

Rusty Hinge wrote in message ...
The message
from (Mike Lyle) contains these words:

I'd love to hear from a structural engineer or similar authority on
this question of tree-roots and house foundations. I imagine, quite
likely wrongly, that modern concrete footings must be too tough a nut
for the roots actually to damage. But would a really vigorous root
system, in time, alter the subsoil conditions so that prolonged
passages of extreme weather (or over-extraction from the water-table)
could result in subsidence even with modern building practices?

Don't you believe it. The roots grow and in effect, use hydraulic power
to do so. Have you never seen a mushroom pushing up through a tarmac
pavement? They will even lift paving stones.

That seems different to me, though I can't quite say why.

On the other hand, old country houses in some places may hardly have
foundations at all:[...]

My parents' house was built on a foundation of willow twigs, probably
more than four hundred years ago.

I think I read somewhere that Paddington Station was built like that
on a raft of fascines: is this possible?
[...]

Mike.

The message
from (Mike Lyle) contains these words:

I think I read somewhere that Paddington Station was built like that
on a raft of fascines: is this possible?

If the ground was waterlogged, yes. I don't think it's included in
today's Building Regs thobut.

--
Rusty http://www.users.zetnet.co.uk/hi-fi/tqt.htm
horrid·squeak snailything zetnet·co·uk exchange d.p. with p to
reply.