On 8 Mar, 12:00, "The Medway Handyman"
wrote:
Looking for a weedkiller to kill off grass under decks. *Weed fabric usually
does the job, but I want to be sure. *Sodium Chlorate?

Good fabric is your best bet - kills grass dead, but there are other
plants that will happily travel several feet in the dark before
emerging. Grass normally can't compete under decks anyway, it's the
others (esp. brambles) that cause the trouble.

Sodium chlorate is easy to get hold of and works for this sort of long-
term sterilisation. Glyphosate and *quat aren't persistent enough to
be any use, although glyphosate might be useful for a first-pass to
kill things already present.

How far do they/does it spread sideways?

As far as the water goes. If there's any sort of slope with runoff,
sodium chlorate could have a run-off deadzone.