Our redwood trees were too big and too close to the house so we had them cut down. Now we will grind out the stumps and remove the large roots. However, the ground is totally saturated with the smaller old redwood roots. What should we do about them before we landscape?
Tree roots stop growing immediately after the tree has been felled, but may take weeks to months (and longer) to die unless the stump has been poisoned with a herbicide. If the stump is not treated, then the roots may send up sprouts, and the roots will start to grow again. While they are alive, trying to advance their decomposition will not work.
It is recommended that any major construction work wait for 6 months after killing the roots so that any ground settlement can occur. If the house were close to the redwood such that the roots were able to extend underneath, then the house may settle a little as well. Presumably your arborist can advise how far the large roots have spread, and whether this is a possibility or not.