They should be fine in containers overwinter if protected from excessive cold. An unheated garage is great.

If you don't have containers large enough, big trash bags will do. However, I might provide some additional protection with burlap or bubble wrap if using those as bags don't offer much insulation.

Don't skip on container size as the largest intact rootball you can manage increases your success. Soil should be just barely moist so check every few weeks and water lightly if necessary. (Poke some holes in the bottom of the trash bag if worried about drainage.)

I heal in plants in my leaf compost pile. You want to make sure they don't dry out completely. I agree with unheated garage, not heated garage. When are you having the work done? One of the things you can do is fill the holes with leaves and then put the plants back in the holes when the work is done. You put a board over the holes so the workmen don't fall in.

I’m having a new deck built in the spring. Contractor said he has to have guys get in to put in footings and such. Will probably trample plants.

Actually liking there hydrangeas in containers better than in the ground. Wish I could keep them on my deck all year in a container.

We have limelight hydrangea trees, knockout roses, and daylilies around our deck. Redid deck a couple of years ago within existing footprint of old deck; didn't need to redo footings or framing just replace the deck/skirtings/railings. Guess I think if you have a contractor worth his weight he should be able to work around the plantings like ours did. Why do they need to replace the footings if you're building within the same footprint?

I had to temporarily dig out a lot of bushes (including hydrangeas) and plants for a multi-month backyard renovation. In a large partially shaded spot, I heeled them in using a mix of topsoil, compost and mulch. Almost everything survived.

Do not crowd and water well/frequently. You may want to stake a burlap perimeter as a winter windbreak.

Thanks. I have all my hydrangeas in 18” containers and they’re on my old deck. I felt doing this now in prep for spring would be best. My house is like a T shape and in the back, I have them on my current deck getting morning sun and some afternoon shade. Also shielded from west and northern winds. In a couple months, as temps dip, I’ll wrap the pots with burlap and make sure there’s a good layer of mulch in the containers.