How to kill weeds on patio floor?

Linda,

i was going to suggest rock dust. Cement may fill in the cracks but the cracks are for expansion. You don’t want to seal it all in.

Try sand or rock dust same thing I think.

Maybe thin strips of landscape fabric under the pebbles? That’s if the cracks are large enough. Then I would add the sand/dust.

Lsu Hi, Boiling hot water should do it.

Weed killers only kill the greenery. You still have to deal with the weed seeds that get propagated when pulling weeds. Hot water might kill some seeds. Some people torch the area to help burn seeds too. I smother with black plastic after a good rain, it rots the seeds.

Take out all the pebbles/gravel. Clean this new area of any weeds. Sprinkle with a granular, long term weed control that kills seeds as they germinate. Cover with a weed barrier cloth, Replace the pebbles.

I did this for my large rock bed & its lasted for over 30 years of being weed free.

Have you tried salt?

Try strong undiluted bleach.

Weed seeds will be blown into the area and dropped by birds, The suggestion that D.m.29724265 gave you was the best way to stop the weeds from coming up. The weed barrier would really help under the pebbles, as well as the weed preventer. I use the Preen Weed Preventer on my gardens and have no problem with seed born weeds all season, but I don't use weed barriers, especially in the veggie and hosta beds. I use shredded leaves and cut grass to mulch them. For something that doesn't have plants the weed barrier is the way to go underneath. You can do one area at a time since it will take physical labor in hot weather.