Unless you are making some major soil amendment changes, I would skip the rototilling.

How bad really is the existing sod? If it still has a fairly high turf vs weed ratio, a good turf care company might be able to whip it back in shape. If it is very weedy, probably better to start with new grass. Depressions in lawns can be filled in easily with topsoil. Grass will quickly grow through it and look normal. (Best to cut grass VERY short before doing this.) If you decide to remove old grass as prep for sod, it would be best to rent a sod cutter and strip if off. If you're going to plant seed, kill existing with herbicide. After it's dead, a light rototilling prior to raking out for seed bed would be useful.

Rototilling will result in a bumpy yard, causing you yard to settle in different areas years down the road as well as disturb and overturn new weed seeds. I strongly urge you not to rototill. You may want to post this in the Lawn forum or either search the lawn forum for "leveling yard." There is a great post that goes into great detail how to do this without removing existing sod. If grass is any decent shape, it will be easy to turn it into great shape with a little work and will be easier on the pocket book. As far as what material to use, builder sand is the best when leveling a yard. Play sand will work, but from what I understand, it may be more rounded and will not interlock like builders grade. There has been some people that have had success with play sand, so I do not see it as a problem if it is the cheaper way to go for you.

I encourage you to search the lawn forum for the post, but as to give you an idea of how to level your yard:

Do this while the grass is actively growing. Scalp your yard as low as you can go without gowing to dirt. Spread sand on yard and water in. You will start to see the sand move to the lower lying areas. I do not remember how frequent or how much water was used, but this will give you an idea. This may have to be repeated multiple times to get the smoothness that you are looking for.

Hope that gives you a start and idea of what to look for.

Hi guys

Thanks for the ideas, indeed it looks like rototilling is not a good idea since I can not control how deep the tiller will grind the soil.
Hmm...this leaves me with the only valid option, to remove the sod and to level and to properly grade the area. I was hoping that the tiller will save me work.
@yardvaark: I need to regrade the backyard, the former owner spread the soil that he excavated when he build the patio and now the patio and the house are lower that the yard around them. The main problem here is the grading not the lawn. Lawn has weeds and I would like to replace it rather than try to fix it

Ivan, if you are asking me a question, I don't understand it.

@Yardvaark(9B): I am not asking you a question. Your answer was centered around the lawn not around regrading the backyard. Adding soil where I have gaps does not solve the regrading

@t_d_harvey I am trying to avoid having to remove the lawn and then putting it back. Since it is not in very good shape I would prefer to turn it over. Your suggestion is in the opposite direction and it does not serve my purpose: to regrade the yard

That is what the subject line starts with: " I need to re grade my yard".yeah, posting in the lawn section might help

In this forum some people create a thread saying what they intend to do and are looking for advice on how to proceed in that direction. Many times, upon getting more information, it becomes apparent to some of us with experience in the field of landscaping, that it's the wrong direction. To be honest, I usually park what the person "wants to do" over to the side and instead try to understand the goals and objectives that are to be accomplished. Those are what determines the work that should be performed. At this point Ivan, I'm not sure what you are looking for, or can get from the advice-givers. What is it about regrading that you wish to know?

Builders’ sand contains silica. It can kill your pets, your kids, and you. DO NOT BREATHE BUILDERS SAND DUST. IT IS HYPER DEADLY.

Most sand - excepting ocean beach sand - has a high silica content. Playground or sandbox sand has a high silica content as it is primarily quartz, yet I can't recall any published incidents of small kids keeling over from playing in it.

Let's not get carried away with our comments, people. 😊