Soil depth

[Bob Smith]

It's the first time I have looked on this group, so forgive me if I ask something straight out of the FAQs, but here goes:

Can anyone tell me how deep topsoil needs to be to grow a lawn?

TIA

Bob

[Short Term Memory Loss]

You don't need topsoil to grow a lawn. Most professional sports venues have zero topsoil, the sod grows on a blend that is at least 90% sand. Oriole Park at Camden Yards had to completely redo their field last year because the organic matter had built up on its own from 17% in eleven years.

T> It's the first time I have looked on this group, so forgive me if I ask

[Moparholic]

Short Term Memory Loss

[Moparholic]

How big is your lawn, Bob? (sq ft)

[Chet Hayes]

Six inches of good top soil should be enough for an excellent lawn. You can get by with less, say 4 inches, but the tradeoff is it will likely need to be watered more frequently during dry spells to keep it green, unless whatever is underneath retains moisture well. If your doing it from scratch, some extra bucks to make sure you have six inches of good top soil, rich in organic material, ie compost, peat moss, etc. is well worth it. It's easy to do it right and impossible to fix later.

[Bob Smith]

What I have is a 10' x 10' area that I have removed some 'decorative' broken brick gravelly stuff from (the kids were always throwing it in the grass, trying to assasinate my lawnmower).

I removed the brick stuff, and still have 3-4" deep of broken rocks and broken down tarmac, then clay soil. I was going to buy 2-3" worth of topsoil to replace the 2-3" of brick stuff, when I found this picture of some grass roots:

may add a few sacks of compost, perhaps some of that moisture retaining gel or formiculite. Am I right in thinking the clay will keep the water from draining away?

Bob

[Moparholic]

That sounds like the right approach, adjust your topsoil to make a decent grade. I'd be more concerned with the broken rock or stuff, than I would be with the clay.

The broken rock may inhibit root growth and increase the soil temperature in that area, resulting in a blighted look during hot weather. Can you remove the rest of the rock before adding your soil?

[Victor Grund]

For those of you who you are stuck with an existing lawn that has less than ideal soil, a useful technique is to topdress annually with a rich organic material (compost). It isn't much work if you can find a company that has a blower truck. They'll drive up in a big truck and blow compost over your lawn to the depth you specify.

Victor

[Bob Smith]

I was hoping not to do that. The amount of 'decorative' rubble I removed (2-3") is sitting in a massive pile next to my front gate. It is the same material as my driveway, so I may do a "Great Escape" and spread it around there. The other tarmac (US=ashphalt?) and hardcore I removed equals some

20-30 bags. Hard work to remove, and then I have to dispose of it. I would estimate at least this amount remaining, and was hoping to save some effort by just putting topsoil on top. Since I live in England, hot temperatures do not worry me! Although a piece of lawn adjacent to my rocky area does look a little hay coloured at times, I had put it down to a sensitive ornamental grass that colonised / took over that area. It is a fine grass, and seems to green up if I douse it. Maybe it also has the tarmac/hardcore underneath. The clay does hold water. I have dug deeper for a flower bed, down to the clay. When it rained, puddles remained in my trench.

Bob