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Raising lawn level - what to do with existing soil/weed

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  • Jun 30th, 2020 10:02 pm
[OP]
Member
Apr 1, 2005
366 posts
374 upvotes

Raising lawn level - what to do with existing soil/weed

I am looking for some guidance and advice. I moved into my current house last year and I am planning to raise the level of my lawn by 3.5 inches to match the height of my patio. I plan on putting in new soil and reseed completely as the existing lawn is quite infested with weeds.

I am considering mass killing all the weeds before i soil/reseed in fall (my understanding is it's not a good time for new grass right now). I tried vinegar/salt/dishsoap method in paved area and it worked quite well in killing the weeds. Is there any issue to mass spray this onto the lawn? I heard that the vinegar/salt will permanently make the soil infertile, but since i will putting 3 inches of new soil, maybe it wouldnt matter?

basically 2 questions:
- How risky would it be to "kill" off the lawn before I add the new 3-inch soil on top? I want to make sure the new soil would be sufficient for new grass to grow later.
- I assume vinegar/salt is more "organic" than other herbicide. My kids will be playing in the backyard so i want to avoid using the really toxic herbicide. Any other recommendation for herbicide?

much appreciated!
9 replies
Deal Fanatic
Nov 22, 2015
6376 posts
6206 upvotes
Why do you need to kill your lawn first? Remove the huge weeds, add the soil, seed, and water frequently

If you overseed and water enough, the weeds should get choked out
Deal Addict
Mar 22, 2017
2125 posts
2603 upvotes
West GTA
Do not salt your lawn. Vinegar will kill immature and shallowly rooted plants, but not mature or deeply rooted ones. Glyphosate isn't toxic, I'd use that. If you really don't want to for whatever reason, then you can use other methods like tarping the soil (use clear plastic in the summer), which will bake the plants and also kill weed seeds right at the surface. This takes a couple of weeks of summer heat to thoroughly kill all plants underneath.
[OP]
Member
Apr 1, 2005
366 posts
374 upvotes
There's just so much weed, especially the spiky ones are coming out now too, hate them with a passion. Such a pain (literally) when pulling them out.

Is 3 inch of new soil and grass seed enough to choke them out?
Deal Addict
Dec 25, 2007
1267 posts
749 upvotes
GTA
use clover. it will out compete weeds
Newbie
Jul 1, 2019
23 posts
8 upvotes
try covering the lawn with cardboard or layers of newspaper and then add your top soil and compost on top. The cardboard/newspaper will kill the weed and grass and will decompose over time (newspaper will decompose faster). Search "Lasagna mulching cardboard" or "sheet mulching". This may be more effective than spraying for your situation.
Deal Addict
Nov 27, 2013
1554 posts
2161 upvotes
Spray everything with roundup a week or two before putting in the new soil
Member
Jan 10, 2017
296 posts
224 upvotes
You can definitely go scorched earth on the existing lawn but don’t be surprised if some weeds will still pop up - I’d go with a gradual approach, spray some herbicide in the fall, wait a few weeks, dress, and overseed and water. Rinse and repeat until the grass chokes out the weeds.

Another approach is to bake the existing lawn, till the entire yard, cover with tarps and let it bake esp with the hot weather coming up. Once baked and crispy by fall, till, dress, seed and water.

Buy good grass seeds
Member
Dec 4, 2009
485 posts
371 upvotes
This is a terrible thread. Rent a sod cutter, remove the existing lawn, re-grade and re-sod. Chemicals and seeds are the slow expensive way. You’ll create more problems than solutions with all of these wacky ideas...

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