"peter" wrote in message
news:K0h9e.21198$H_5.14634@trnddc01...
I want to redo the lawn in the backyard because it had too much weed, moss,
and the ground does not slope away from the foundation enough (my crawspace
gets wet).

The plan is to till the soil, add compost, add a french drain, regrade the
slope and then reseed the lawn.

After killing off the existing lawn, I found that under the surface it is
crisscrossed with tree roots up to 2-inch in diameter. They appear to come
from a birch tree in the corner. I yanked out some of those roots and have
some more to go. Other than cutting down the tree, is there a way to
prevent the roots from invading the lawn in the future?

Also, the soil seems very clay-like. In fact, when it rains some puddles
would form and drain away very slowly. Should I do something about this,
like add sand?

Some books suggest the french drain be put near the foundation wall. I
fear that losening the soil near the foundation would weaken the support
of the foundation, so I'm inclined to put the french drain on the
perimeter of the lawn, i.e. the lowest point after it is regraded. Would
this work?

Shallow tree roots may be a sign of too frequent watering or standing water,
or very shallow water table. Trees shoot out surface roots when they are
drowning, or lack oxygen due to impervious clay soils. Before trying
anything drastic, I would water the lawn infrequently, but deeply. That
tends to grow grass better than weeds. It also causes grass and tree roots
to grow deeper, making them more resistant to drought. If you are already
in the process of regrading, the drain and resloping will help, but not
without changing watering frequency as well. Sand does not help drainage in
clay soils, it turns it into concrete like stuff. Organics break down clay
quite nicely. You should consult a lawn and garden book for your area, and
pay special attention to watering and soil conditioning practices. Your
local ag extension office and nurseries will also provide brochures on how
to improve clay soils.