You cannot 'expect' anything. It's hard telling what you will or will not find back there. If the chimney has been removed there was likely a reason it had, so you may even find bricks in the firebox, where the chimney had been deteriorating and crumbling into the stack, or bird bones where they'd flown down there and got trapped. There may be decades of wood or coal dust settled into the pit, or it may be clean and tidy. You won't know until you open it and look. We do not use our fireplaces for woodburning anymore, although my husband used to use the one in the kitchen. We had a fireplace in every room of the 1820s house. Some of them had been cemented shut before he bought it, and some of them he dry-walled over and some of them he left just sealed with mantles intact. The one in the living room, although it's open we don't use and yes.........it's open with glass doors and used decoratively. One of these days, I'd like to install a gas line coming up from the cellar and put in vent-free gas logs. The kitchen hearth is also open but we fitted in an antique looking cast iron gas grate and it's very practical for us when we don't want to kick on the boiler system in fall or spring. As for venting flue gasses up old chimneys. That's fine if it's a safe chimney and has been checked for leaks and you are sure it's open and your local codes (if applicable) are not violated. Hopefully somebody checked out the patency and integrity of the chimney before they did it. If you do have a chimney problem, your gas appliance may as well be not vented, however and it may impose an unsafe situation as far as carbon monoxide. I had an investment house in town, and installed a new furnace and gas fired hot water heater. The installer vented the high efficiency furnace through the wall, because the hot water heater was already vented through the chimney and codes allowed only one appliance to be vented through each stack.

Yes the grout should be sealed. Helps protect the grout. Helps delay the inevitable. As far as I'm concerned, sealing grout is one of the biggest scams in the industry. I do have to qualify that statement, though, by saying that I'm in the minority in that thought. The thing is if you decide to use a white or off white grout-- something real light-- in high traffic areas, you're still going to show traffic patterns. You're still going to end up with staining, and the grout will still slightly darken as it gets older, from minerals and so forth in the water as you wash the floor, not to mention the dirt that gets rubbed in as you clean. There's just no way around it. You're much better off with a medium to darker color grout that won't show it as much. In the long run, you'll be alot happier. Although I've been working full time for 29 years now, I grew up in the trade, setting my first tile when I was 10 (41 years ago), when my father built the house I grew up in. but my father (and grandfather, for that matter) was a tile contractor, as well, and I've never once-- not in my Dad's house, or my own, nor in any of my 4 sisters' or my brother's homes, have I (or they)ever sealed one inch of grout joints. As for sealing tile, other than natural stone, as far as I'm concerned, the only tile that should be sealed is crackle glazed tile. There are some old generation porcelains that needed to be sealed because they did tend to stain. But the newer porcelains, if you try and seal them, all you'll end up with is tile with a heavy white haze on it that's tough as nails to remove.

I have marble subway tiles for my entire kitchen and I sealed it with Miracle 511 Porous Plus before my GC installed them. Every time I cooked there's some level of splashes and I wiped the entire backsplash area behind my cooktop at the end of that day as part of clean up. I haven't notice any etch from looking straight at my backsplash with and without my hood lights. I can go home tonight to look at it from different angle to see if there's any etch but at least with my hood light on, I can't tell. It's been a year and I think I will reseal the backsplash again.

I'm going to start from your last question. You'll definitely want to use silicone, color-matched if possible, to do the seam between your finished quartz and the first tile of your backsplash. That will help with water resistance and also give you some flex. You'll probably be fine with silicone underneath to secure the quartz to the brackets, but I wouldn't count on silicone raising the quartz to the appropriate level. You either need to re-position your brackets slightly or shim it to get it to the best height where it will stay. Silicone could flex and strain the seams if your quartz piece isn't securely set at the right height. As for finishing the two seams, a pro would use something that would be near permanent and very difficult to remove in the event of future problems, also something color matched that would be inconspicuous. They'd also have equipment to pull the sides of the seams together tightly, but since you're working with two pieces on the sides that are previously affixed, you won't be able to do that. There is some type of solution I've seen discussed in these forums that can be ordered color matched for this job, but it would take a while to go back through my saved information and find it. Maybe Joseph Corlett or someone else will see your post and comment. If not, let me know, and I'll try to find it for you. You might want to just do the seams with silicone for now so that if anything else goes wrong, you can re-do the job without damaging all the pieces of quartz trying to take it apart again.