Question
My husband and I have a new construction home and we are in the process of starting a new lawn.  The site is presently covered entirely with crab grass and weeds.  We are bringing in 2 inches of topsoil, however we were told that we do not need to kill all the existing crab grass and weeds in order to start the law.  We were told that we can simply mow the existing vegetation very low and lay the topsoil on top of it to start our new lawn. Is this correct? Should we kill all the existing vegetation prior to laying the topsoil? If so, how long after spraying the chemicals to kill the crabgrass/weeds do we have to wait to lay the topsoil and start seeding?  We are starting this process next week so a prompt response would be greatly appreciated.
Sincerely,
The Santana Family

Answer
Hi Mecca;
This is perfect timing.
You can start from scratch, do a little more preparation now, and set yourself up for a successful lawn without years of struggling, and then having to start over.
Make sure you have good soil to atart with.
Builders just lay a tad of topsoil, and they don't do anything to amend poor soil conditions that already exist.
check out what the soil is like for about 6 to 8 inches down.
You want good soil with good drainage, or you will just set yourself up for trouble down the road.
If there is too much clay or sand, You can till in the thing now tht will correct that.
when you pick up a handful of soil ( with normal moisture, not muddy from recent rain, or dead dry from a drought), and sqweeze your hand shut, and then open it flat, part of the soil should form a not too tight ball, and some of it should break away.
If forms a firm ball and no soil breaks awat at all, then it has too much clay, is too tight, will not drain well, and will not allow enough water to soak in the sustain your lawn, except weeds.
You need to till in some amendments to loosen it. Humus, peat moss, and bark mulch, maybe even a little sand.
  If it forms little to no ball, just flakes apart, then it is too loose, and you need to add something to firm it up. Probably soil with more clay in it. I don't have any experience firming up soil. what I have always had was clay soil I had to loosen up.
Now, after you determine if you have to loosen or tighten it, just get the amendments you need to add, sump them all over so that after you till it about 8 to 10 inches deep, with the existing soil, you wil have 8 to 10 inches deep of good, drainable soil that will be firm enough to sustain the root system, but loose enough to allow for good drainage.
I don't mix the amendments before I add them, I just dump them and spread them, then till the whole thing until it is thoroughly mixed with the existing soil to make it all just right.
You don't even have to mow the weeds. You run that tiller and mix until it is mixed as well as cake batter would be, and the weeds will all be chopped up fine, and mixed in, and they will decompose and add to the nutrients, and help feed your grass.
then if you want to roll it to tamp it down some, you can. When i do tilling and mixing, I just rake it smooth and water it gently ( so as not to make it wash out unevenly, and let that soak in and do it again. till it is nice and wet, and as the water drains through it, it firms it up some.
If you ae going to sod in your lawn, you can just till up. rake it, and pay the sod, then water, and when it is nice and soggy, walk on it, sqwishing the sod into the soil some, to help the roots catch  hold.
Look for earthworms. If there has not been chemicals dumoed on the soil and there are earthworms there, goo. If nt, you may want to buy some and dump them in after you till.
If they are there, some are going to get chopped up by the tiller, but some will not.
after you put the sod down, or before, doesn't matter, put down sugar at the rate of 1 pound per 250 sq.ft.
then do the watering.
    Have you read any of my answers about using sugar to enrich the soil?
Weeds don't thrive in rich soil. they like poor soil.
make rich soil, and weeds will not be a problem.
This is a perfect time to get started off on a good organic lawn care program. You are working with a blank canvas. Create now, a perfect growing condition so you can have a gorgeous lawn, and while your neighbors are breaking their backs trying to coax a good lawn along, you will be sitting sipping tea and loking at your beautiful lawn and garden.
Organics is kore about what you DON'T do,than what you do.
Create the right lawn condition ( the way God laid it out to work in the beginning) and all the little lawn critters, toads, grass snakes, lizards, and beneficial insects, will take care of the pest insects better than chemicals will. You will not have to battle grub worms, army worms, aphids etc.
The beneficial microbes in the soil will work round the clock, enriching the soil, so you will not have to fertilize, use weed killers etc, the weeds will not thrive in your nice rich soil.
I can't tell you haw much I spent and how many back breaking hours i spent trying to get a lovely lawn and garden.
I battled evert weed in the book, and every bad insect in the book, and had a fairly decent lawn and garden, that I would come home from work, get dinner, clean house, get kids ready for bed etc, then go out and work 3 or 4 hours on my lawn.
Now I put sugar in the spring and again in the fall, and use bakig soda sray for fungicide.
My husband mows and edges, and I water. NO WEEDS!!!! NO BAD BUGS!!!!
The money we spend, and the time we spend working in out lawn, is buying and planting new flowere and shrubs.
I haven't bought a chemical product in at least 8 years, ( for inside the house either. I use organics for indoor pests, and I no longer ever see one.)
My husband and I went out on the deck around 11:00 o'clock last night, just to chat a few minutes before ging to bed.
It was such a lovely night, and everything smelled so clean, and no chemicals, and we had a strong whiff of my roses and jasmine ( things are just starting to bloom here), and we finally came in at 2:00am.
We hated to give it up and come in. LOL
Let;s start now to set you up on an organic program so you can have a lovely lawn you can spend your time enjoying, instead of working on.
I am happy to answer any questions you have so you can gain this good experience of enjoying your new home, and have a lovely, weed free lawn to enjoy.
Write as often as you have questions or need me to clarify something i have written to you.
Charlotte