That grass sure looks dead to me, which is an unfortunate waste of money and sod. Dormant grass is generally tan,yellow, or an off green color. Gray grass is generally dead. I suppose an extreme case of gray snow mold could make grass look like that, but if it pulls up very easily like in your pic, then it's probably dead. The fact that you can actually make out the edges makes me wonder when this sod was laid, and if it was ever healthy. While it may be 15 C (59 F) where you live, turfgrass is more responsive to soil temperatures. If your nights are freezing, then your soil may not be warm enough to end dormancy, but again, this doesn't look like dormant grass to me.

Seed needs to be in contact with soil, not on top of dead grass. A power rake might be enough to break up the dead sod, but if it doesn't, you might have to remove it.

The best time to seed a cool season grass is late summer/early fall. Grasses seeded at this time have ideal soil temps for germination, warm days and cool dry nights, no heat stress, and little weed and disease pressure. Spring seeded turf has lower soil temps, so germination takes longer, weed pressure, and stress from summer. Being in Canada however might mitigate some of these stresses, but you should wait till soil temps get to about 55 degrees minimum, 60 would be better.

I would use Kentucky bluegrass for sunny areas and/or fine fescues for shady ones where you live. Tall fescue and perennial rye might have issues with cold kill, although I am not that familiar with your climate. Most mixes in big box stores contain perennial rye for quick germination, but often this means people don't water enough for the other grasses to germinate and establish, and the perennial rye becomes the dominant species.

@tiemco, thanks. I'm currently in the process of removing all the dead sod. It's coming up really easily (I just lift a corner and then roll it up like a carpet).

I'll be ordering about 12 yds of topsoil to blanket the yard areas. This should give me about 2 inches coverage on top of whatever is there. It looks like 2-3" is recommended and there's still quite a bit beneath the old sod, so I think I should be OK.

--anjp

Just to calibrate your new soil, you should not pile it up higher than the surrounding concrete. It should be just about at the same level. As the roots enlarge they will raise the sod slightly above the level of the concrete. 12 yards sounds like a LOT of soil.

Where did you read that you should seed grass in the spring? Tiemco only touched on the problems with spring seeding. If you are going to go ahead and do it now, you might as well use inexpensive seed like rye. Then in the fall (August for you), you can reseed with a much better seed like Kentucky bluegrass and/or fescue. The problem that tiemco didn't get much into is that the seed you put down now will suffer from the summer heat stress. But that might be minimal in your area so you are taking a chance. What does not suffer from the heat is crabgrass. Crabgrass is designed for summer heat and it's germinating right now. I you try to germinate lawn grass at the same time as crabgrass is germinating, the crabgrass will win.