DO NOT hire GATT for any service. Everything extensively went wrong in every department - right down to the plumber walking through our house (white carpet) with muddy boots.
Plumbing - had to get water lines redone. They switched the hot & cold in one area, had to come back TWICE to fix it (2 taps only affected)
Furnace - installation - staff left bolts in the fan which would rattle and make noise (not pleasant at 5 am). Then didn't level furnace, then didn't turn on the vent to suck in outside air. (and wires are still crossed now - and we have to fix this part on our own)
They left the HUGEST mess when they were here. We can access outside through a side door, so they took full advantage of this convenience which left me with hours worth of cleaning over the MANY MANY times they had to come back to actually complete a job! Some trades didn't call prior to showing up, just came. Scheduling on their end wasn't communicated very well to us either. Invoices are horrible, do NOT reflect what was actually paid for. Need to reference quotes (if you even got them). It was not a smooth experience from start to finish. AND IT STILL isn't finished. Do not repeat what we had to experience.