Re-grading around patio
I need to do some re-grading of my lawn in the backyard around the concrete patio under my deck. The lawn is low on all three sides, and is bad enough on one of the sides that the gravel underneath the concrete slab is coming out and you can see the underside of the slab.
On the two sides seen in the photo the lawn slopes down and away towards my neighbors backyard (which is lower than mine) so I presume I can just add topsoil to bring the grade up to the top of the slab and feather it out over 6-8 feet or so to blend it into the grade of the rest of the lawn? I'm planning to do away with the planting area along the one edge and just plant grass right up to the slab.
You can sort-of see in the photo that on the opposite side the lawn slopes down towards the slab; I'll post a picture from a different angle in a follow-up.
1. How's my timing? The weather is just starting to be consistently in the upper 50s/lower 60s after this awful winter. How much time do I have to get the grading done and be able to seed before the weather gets too warm?
2. As you can see, the remainder of the lawn isn't in super-great shape, and I'm planning to put down some crabgrass preventer (Barricade most likely, without fertilizer) soon. I presume I should stay away from the area where I'll be re-grading, lest the crabgrass preventer also prevent the new grass seed from germinating?
3. How do I go about determining how much topsoil I need? Since the area being regraded will wrap around one corner and I need to blend it into the existing lawn, I can't just do the math for a rectangular area of uniform thickness. Also, do I need to account for settling/compaction of the topsoil once it is put down?
4. Do I need to remove the existing grass in the area where I'll be re-grading, or can I just put topsoil right overtop and feather it away from the slab to blend it into the existing lawn? One website suggested that existing grass will grow up through an inch or two of topsoil.
5. I'll be bringing in topsoil to do this -- I presume screened topsoil is my best bet?