While "silver birch" tells us something, can we get your nearest city and state? It'll tell us a lot more about your optimal seeding dates and type of grasses.

As a general rule, breaking up soils isn't necessary and does a lot more harm than good. You may see that soil as impossibly hard. The grass seed's root just sees it as a mild challenge. Roots can and do crack rocks.

But until we have a place and grass, recommendations would be tough.

Also you said you were watering regularly. What is your watering schedule? How often and for how long do you water throughout your growing season?

Northern Suburbs of Chicago, IL....the Silver Birch tree is in the front of the house (North Facing and opposite side of the house where I am having the onset of brown grass). The grass has always been thin near the Silber Birch and you do see some of the surface roots of the birch, but not quite as exposed as you would see with a Willow.

My watering would depend on rain levels, but in the driest part of the year I would water it about 30-45 minutes once to twice a week

There's a good chance your neighbor doesn't know what problem he has/had. Grubs are easy to find. Dig up 1 square foot of turf. If you can count fewer than a dozen grubs, you don't have a problem. If you have an uncountable mass of grubs, then you have a problem.

A lot of people don't know what crabgrass looks like and believe that the weed they have is crabgrass. The problem is trying to treat a weed that is not crabgrass often does not work. Crabgrass is a summer annual plant that will get a good start in mid to late spring IF THE SOIL STAYS WET FOR A FEW DAYS IN A ROW. Crabgrass seed needs full sunlight and continued moisture over several days. If you maintain tall turf, say 3+ inches high, that will go a long way to preventing crabgrass from ever getting started. But if the grass thins out from disease or grubs, then crabgrass can break in the following spring. But it also needs continual moisture. This is one reason why seeding northern grasses in the spring is a bad idea, because the same treatment used for germinating new grass seed is ideal for germinating crabgrass seed. And the crabgrass will germinate faster than any of the cool season grass seeds giving you the impression that you're a lawn genius. Many people will pull back on watering just before the real grass seed germinates. What they end up with is a full crabgrass lawn by July. Crabgrass will completely die after the first frost of autumn. With this in mind, I'm going to suggest you do not water twice a week during spring and only do that when the temps are real close to 100 degrees F. Once a week with temps in the 90s should be fine as long as you water 1 full inch, all at one time.

You can treat your hard soil by spraying it with baby shampoo at a rate of 3 ounces per 1,000 square feet. Or you could do 3 ounces per 100 square feet. It's not going to hurt anything if you use too much. Follow that up with 1/2 to 1 inch of irrigation or rain to take the shampoo deep into the soil. If water runs off rather than soaking in, stop watering immediately and wait 15 to 30 minutes for the water to soak in. Then resume until you get the 1/2 to 1 inch. You can measure the water with a tuna can or cat food can. The shampoo works by setting up the perfect environment underground for holding moisture and keeping it cool. The microbes living in the soil will soften it for you. Give it 3 weeks to see the improvement.

If you have bare spots now, rather than seeding in the spring, it would be better if you could cover it with sod. The sod will help keep the crabgrass seed from germinating if it is already there.