Tile Setters vs. Trim carpenters
On a woodworking site, it's not tough to guess the winner of this battle. But the war of words makes for good reading. February 25, 2005
Here's the situation: Tile setter is scheduled to start two days after trim carpenter (me). Door units are already set and he is extremely upset because he will have to use jamb saw to cut off jambs (isn't that what jamb saws are for?). In addition, he will be installing pre-finished hardwood floors and doesn't want any base installed. Normally, this situation is no problem with my regular builders. This is a homeowner-contractor and he doesn't have a clue as to how he prefers work to be performed.
I usually hold base up 7/8" to allow flooring to slide under, then install shoe molding later during lock-out. Jambs are normally cut off the thickness of tile plus backer board so tile slides under the jamb, resulting in a clean, tight fit.
This was an ugly scene that resulted in the tile setter storming off the job muttering something about my mother and her dog. (She doesn't even have a dog!) How do you handle who goes first? What seems to work best for you in this situation?
(Cabinet and Millwork Installation Forum)
From contributor R:
The tile setter is always first.
From contributor P:
Will the work of the tile setter and flooring guy get in the way of the trim guy? Will the baseboard and doors/casing get in the way of the flooring guys? There is your answer!
From contributor W:
If you had to do both jobs yourself (the tile and the trim), which would *you* do first?
From contributor J:
The doors and trim should be installed, and stained or primed/painted first. Who in their right mind works over a finished floor? Homeowner should be able to figure that out, and not make a pain in the butt for every sub on the job because someone doesn't want to buy or use a jamb saw.
From contributor G:
Doors and trim are definitely first. I have never seen it done the other way, unless it was an extensive remodel job. As a previous post says, that's what a jamb saw is for.
Also, you don't need to hold the base up 7/8 so the flooring will slide under. That is what the shoe is for.
From contributor P:
I just set a tile floor this morning for a GC that only does trim. The door was not set and the bottom of the walls are being treated with wainscoting, base and shoe. That was not done either. I work over finished floors all the time - no big deal. I understand that nobody wants to work over a finished floor. If I was GC, the flooring would be done first, even if I was the one trimming it. Period. I have also seen cabinets installed first - that is BS, too!
From contributor J:
I would have to disagree with the last post. A mud set floor should be grouted to the cabinets and base moulding. In my opinion, nothing looks cheesier or cheaper than shoe moulding on a tile floor. Shoemould is for hardwood flooring or sheet vinyl/linoleum. Most often, the tiles are set so that you can't shoemould them anyway with the corners sticking up.
Has anyone tried to fit cabinets or crown to a rock fireplace on which no one had the foresight to run a frieze or at least lay against a straight edge? A GC should be publicly flogged for allowing that to happen. I just set a job about 3 weeks late waiting on a tilesetter that convinced the homeowner the tile should be laid first. He wasn't busy at the time, and thought he might be when the job came on schedule. He got done and his rusted up trowels and other junk laid piled out in the carport for the next 4 weeks! Besides wasting 80 sq feet or more of tile under the cabinets and making the installation of the linen cabinets next to impossible with a bathroom wainscot of tile, what was accomplished? Now the trimmer has to fit all the jambs to this snaggletoothed tile, and the painter has to spend 1 day putting paper down before he can paint. Luckily, the homeowner came by with a new cordless drill he just bought and dropped it on the floor and broke one of the tiles. He was installing a threshold to cover where the tile didn't make it to the hardwood floor (again, cheesy)!
From contributor T:
Wait! I have a better one. The designer wanted a bar in the living section just this side of the kitchen. Fine. All I said was "check with the plumber to make sure that the plumbing will get over here for the sink."
I did a really nice mahogany bar. The designer says that they want to order the black granite top first. I told her that the top is a semi-circular shape with wood edge rail. Nonetheless, this is what they did. Come installation day, they had to cut the granite in three pie shapes to get it in. Real trashy. Here comes the best part. I went behind the bar to look at the beautiful nickel sink and I opened the custom concave door below the sink and there it is. A 5 gallon bucket for drain waste.
From contributor R:
I've seen it done every way possible. It depends on how nasty the jobsite is. Here's the proper way - hang all the doors and trim except where there's tile or lino. You can go ahead and do that as well, but you create extra work for the tile/lino guy. If I have to do this, I use a piece of tile and corrugated cardboard as a spacer, so he doesn't normally have to trim my casing. After the tile/lino is done, I install the baseboard - no shoe mold ever! I take the base and backbevel the bottom and scribe to fit, which takes about the same amount of time as a shoe mold and you don't have to look at the hideous ends where they butt into the usually cheap undersized casing.
From the original questioner:
I know there are valid arguments to be made on both sides of the fence concerning tile/trim. This is an old argument that seems to rear its ugly head every year or two. In my opinion, what it comes down to is what makes for the best looking job with the least problems.
I believe setting doors and base first creates fewer problems than the other way around. As I mentioned earlier, cutting the jambs off allows for a clean, tight fit. If the base is held up the thickness of the backer board and tile plus 1/8" or less, then the gap, if any, can be easily grouted with the rest of the floor, or caulked if you prefer, not requiring shoe molding (which I agree looks cheesy at best).
As far as installing pre-finished hardwood floors goes, I believe this should be the last thing done before carpet. There is too much of a chance to damage the floor prior to this time.
Of course, I can work over a finished floor (tile or wood). Sometimes it is necessary, but as a general rule, I think installing doors and trim creates fewer problems and makes for a better looking job.
By the way, the homeowner/contractor called his brother-in-law who is a builder in Michigan and asked him what should go first. Doors and trim was the answer. Then he called a couple of other contractors he knows. Same answer.
From contributor F:
Trim carpenter goes first for all the reasons mentioned above.
The tile guy in this case must not be much of a tile guy, if he is whining about having to use a jamb saw... big deal. I would be looking for another tile guy!
From contributor M:
Down here in Georgia, we prefer that the tile and unfinished wood floors be installed first. In my experience, tile setters and wood floor installers are notorious for butchering up door jambs and casing. Many times, their blades are dull, leaving a ragged cut. Many times the cut height is not set accurately, leaving a gap between the casing and tile or wood floor. Sometimes there are joints in the subfloor that are not level, which throws off the jamb saw, making a crooked cut. As a finish carpenter, I am responsible for as near a perfect finish job as possible, and I don't want to leave that in the hands of a tile man or floor layer. I can make my door jambs and casing fit tight to any floor, whether it's level and flat or not, resulting in a better fit. I disagree with the gentleman who says shoe mould looks cheesy on tile floors where there is wood baseboard. What looks cheesy to me is the crack at the joint where grout meets wood, which always occurs.
I realize that things are done differently in different parts of the country. In 30 years of carpentry, I've done it both ways, depending on the situation and the builder. I think that owner/builders are the worst, as they aren't experienced at job coordination.
From contributor A:
Contributor P, your post really got me fired up. Just because something is easier for you doesn't make it the right way. Why are so many tile guys scared of their tile saw and jamb saw? You know, it's easier for the drywaller if there are no electrical boxes in the wall. Maybe the electrician should do that later...
Any finish carpenter will agree that setting a jamb head level while keeping both legs tight to the finish floor can more than double install time and never looks as good as one jambsawed and/or grouted. And I cannot tell you how much time I have spent scraping the excess grout along the wall (or back-cutting the base) so the base will set somewhat tight to the floor. And have you ever tried to wrack a cabinet with inset doors square when you can't put a screw through the toe kick to hold it? Many times I do both jobs myself, and the trim is always done first.
I'm a little steamed right now because last week I had a tile guy try to convince a homeowner to let him sneak onto my job (I'm contracting all aspects of the job except the tile) first. The mechanical isn't even done and to make matters worse, it is a slate floor. Try setting your cabinets on that uneven surface. And shoe? Out of the question. You contractors out there know how hard it can be to convince a customer to do something right after someone has already fed them a line of bull.
I'm all for making everyone's job easier, but not if the quality or beauty of the job is compromised. My customers know this and that is why they hire me.
From contributor A:
We talented carpenters can make it fit tight. But I never relish picking up someone else's slack. If a tile guy cannot use a jambsaw or does not maintain his equipment, he is not on my job.
I contract most of the jobs I trim and install cabinets for, so naturally I am there tearing the old kitchen/bath out. To this day, I have never torn cabinets out of an old, high-end home and found tile under the cabinets.
From contributor P:
To set the record straight... I am a carpenter. Mostly renovations. Try getting a tile under a jamb and keeping it tight to the bottom of the jamb with the mortar wet. PIA. I can't understand why on earth it would double the install time to set a door on top of tile. Put a level on the floor, note if it is out of level, and trim jamb - no big deal. For your information, having a door set before tile is really no big deal. Trimming it and/or base is a pain for the tile guy. I am both almost always. Base first, before hardwood flooring, is nuts. Why not at least leave the trim off where it meets the hardwood or tile? I understand the trim guy wants to finish and get paid. Why not leave it for the punch guy on new construction? Have you ever done tile? Or flooring?
From contributor A:
I don't think the tile should be under the jamb any more than it should be under the finish toe of a cabinet. I personally think it looks best with the same grout line around the perimeter. That way, the tile looks fit to the space. If the tile is set under the jamb, I manage to set it tight (I do tile as well). Let us also note that we are not talking about hardwood here (which I also install). When finished, it has a smooth surface against which shoe sits tight. A wood floor also has expansion issues that tile does not have and it is sanded and finished at a later date (assuming it's not pre-finished).
You don't understand why it takes longer to set a jamb on a finished floor? Especially if the tile has an uneven surface or it's slate? Let's see - take door out of jamb...Use shim under jamb to set correct height... Plumb... Drive nail... Hang door and visually make the top reveal perfect... Nail other side. Now the other way. Determine height... Make level line at that height and measure to finish floor (or lay level on floor and guess if you're actually seeing 1/8 or 3/16 or slide shim under level until reads level, mark the shim and measure the shim)... Take door out of jamb and mark and trim jamb. (If you cut the jamb by hand, you need your speed square and an additional saw. If you use the mitre saw, you use your helper or a stretcher to hold up the other leg while you cut it to length. If you're making your own jambs, it's not as awkward.) Now set the jamb plumb... Hang the door (this is the moment of excitement and suspense - will the top reveal look even or not?).
I didn't like your comment about setting the cabinets first being BS. There is a multitude of reasons for setting the cabinetry first. I'll give you one. Say I have a fridge on the end of a run of cabinets with an end panel. How do I neatly fasten the panel to the floor (please don't tell me caulk or L bracket)? What about a free standing 12" base cab? Oh, that's right - go get my hammer drill to fasten a nailer to the floor (the same for peninsulas and islands). Not to mention the nasty look of shoe on some tile, and how hard on my knees the tile is, and how twice my workers have dropped the glass touchup bottles on the floor in multi-million dollar homes, and how dropcloths have to be placed under my ladders, etc.
If I have to, I will gladly jamb saw the trim for the tile guy after the mud base is done. If I have to compromise, I'd be willing to set the door jambs and cabs only and do the casing and base later. If I have to, I'll let the tile be set first and take the time to scribe to it... but as a rule of thumb, the trim should be done first.
From the original questioner:
Contributor M, I don't know where in Georgia you are, but I lived and worked there for 14 years (Peachtree City) and subcontracted trim, cabinets, and stairs for numerous builders. I can only think of one of my regular builders that installed tile and/or wood floors prior to trim on a regular basis. Oh, there would always be occasional scheduling conflicts and screw-ups. But generally, trim went first. However, you are dead on accurate in explaining the pitfalls of having an incompetent tile/flooring installer butcher up jambs with dull saws and inaccurate cut heights. This is not the fault of the trim man! If I am asked to fix the problem, then I charge for it and the builder back charges the floor installer. It usually doesn't take long for them to learn to be more accurate or a new installer will be found.
Contributor A, you sure hit the nail on the head about keeping jamb heads level and legs tight to the floor. What a pain! And scraping grout out of corners and back cutting base? Been there, done that. Anyone who doesn't know why it would double install time to set a door on top of tile or wood hasn't done many of them. Just reading a level on the floor isn't enough. Besides that, many times the rough openings aren't tall enough to install a door unit on top of wood or tile.
I too have installed trim both ways in 27 years doing trim and would agree that a lot depends on conditions, the builder, and local practice. But as I stated in an earlier post, what it comes down to is what creates the best looking job with the fewest problems (there will be problems), in your particular situation.
FYI: Tile setter will start on Monday. The painter is also scheduled to start on Monday! And the cabinets (Thank goodness I didn't have to install cabinets on this job!) are scheduled for the following Monday (poor guys!). I think that's the same day the pre-finished wood floors are scheduled. Man, am I glad to be through with this job.
From contributor M:
I live and work on Lake Oconee, one hour east of Atlanta. In this area, all of my builders install wood floors first. Tile, sometimes depends on the material, and sometimes just availability of the tile guy. The house I'm currently doing has 18 x 18 travertine tile floors in the master bath and it was installed first. As you know, many times the tile guys are working at the same time as we are, and it's just a matter of who gets there first. There are five 8' solid core doors in this particular bath with 3 1/2 poplar casing with backband, and plinth blocks. The plinths are 3/4 on the inside edge, and 1 1/2 on the outer edge. In this case, I'm glad the tile was in. I like knowing that these heavy doors are sitting on a solid floor. I hate to think what the tile guy would have done to the plinth blocks. I agree that it is often a touchy situation and almost always a pain dealing with all the other subs as well as the poor quality of those who go before us, like framers who can't measure or use a level, or sheetrockers who can't cut the rock clean, or tile setters who cake grout all against the wall or fill corners with grout that have to be chiseled out. I, too, charge extra for everything I have to do as a result of someone else's sloppy work and seldom do builders complain about these charges. The homes in this resort area are fairly high end and the owners pay for and expect high quality. So, whatever it takes, we do, and we charge.
Let me add that, of course, if the floor was pre-finished, it would go down last. Actually, in all these years, I have never trimmed a house with pre-finished floors. What am I missing...?
From the original questioner:
I agree that in this case it is preferable, if not necessary, to have tile done first. There will always be times when this is the preferred method. The situations I refer to, for the most part, are installing pre-hung, hollow core door units with standard 356 or Howe casing. If I cut and install casing and plinth blocks, it's not as important which is done first. Actually, when the tile guys are working at the same time we are, it's usually easier to work out a solution among ourselves than to let the builder make the call.
You haven't trimmed a house that has pre-finished floors? There are good and bad things about that as well. But that's another subject.
I'll tell you what upsets me more than just about anything else. That's trying to install a staircase and balustrade over stringers so screwed up, out of level, out of square, with unequal rises and runs that the entire thing has to be rebuilt and I'm so ready to strangle the framer.
From contributor K:
In Mass-RI, we almost always are the second to last on the job, with the painters being last. Setting doors on finished surfaces is how we usually do it. I spin a laser at jamb height and measure all legs and cut bottom of doors for proper reveals. I do think setting the door first would be nice, but are you going to leave cutting doors to the floor guys? Not to bash floor guys, but over here they are not the most accurate types on the site. If the tile guys have to meet wood, how are they going to run their saws all the way across the jamb?
From contributor I:
I can't see it's necessary to cut the jamb. Only the casing would need to be cut, then fit the tile or wood to the jamb face. We're not trying to pilot the space shuttle - we're installing floor covering. Trim carpentry isn't rocket science, but it burns me up for another trade to want me to prep his job "because he can't." Either learn your trade and deal with it or go to work at Target (probably in shoes).
When I roll on the job, I have what it takes to get my job done. Other trades want you to pull their slack. I got a call Saturday from a homeowner/builder that his electrician needed me to drive 45 miles to cut in a receptacle box in the end of an island because he was afraid he would mess it up. Give me a break. If you can't cut a square hole close enough that one of those jumbo cover plates that I would keep in my glove box won't cover, do something else!
From contributor K:
I hear what you are saying but I know from experience that other trades only care about what they are doing. They do not care if they knock a board in and move the jamb as long as their stuff looks tight. That being said, it is only the general's fault when it happens for not taking the time to look at the work being performed.
From contributor A:
It is very common to have tile on just one side of a doorway, in which case there is usually a 4 1/2" marble threshold with beveled edges. That threshold has to go between the jambs. I remember a job two years ago where I had to make cardboard templates for each leg of the jambs to transition from the wood floor, up and over the threshold, and back down to the tile (stain grade, no caulk).
The builder/homeowner just needs to make sure the tile guy and finish carpenter talk and work out a plan.
From contributor U:
I can not think how they are going to get the tile tight to the jamb if installed after. Can someone explain this to me?
From contributor J:
I'll take a stab at this one. I don't find it's necessary to cut the jamb across the face, just the casing and clip the door stop, then it's just a matter of cutting the tile to the jamb face. I know this will require some measure of effort and thought on the part of the tile setter. I am a cabinet builder, a trim carpenter, and I have installed tile professionally in a previous life, not that it counts for much.
From contributor E:
In 25 years I thought I had about seen it all until yesterday, when the GC scheduled me, the trimmer, and the wood floor guys (3 of 'em) for the same day in a 2 room remodel! Since I was there first, they went off to a job they could get something done at.
From the original questioner:
Well, it seems as if this issue has no firm resolution. But I guess that is how it should be. As professionals, we should all be looking for ways to improve the job we do. It is so easy to learn to do a particular job one way and never consider other ways to accomplish the same job. Maybe an easier way, maybe a more difficult way but with better results, maybe a more time-efficient way. Who knows? I agree and disagree with many of you and I am sure the thought is reciprocal. But that is what I like about this forum. An environment for professionals to share ideas, cuss and discuss them, argue about them, and maybe just maybe, learn something new when we thought we knew it all. Does this mean that I am going to change how I install doors and trim? No! This is what works best in my situation. Just don't make any comments about my mother and her dog (which she doesn't have) if you disagree! Best regards and remember, don't force it, just use a bigger hammer :)
From contributor F:
We do kitchen and bath remodeling. We are the trim carpenters and the tilers. We might put down cement board first, but the actual tile is one of the last things to happen for all of the reasons given above. The only reason I can think of to tile first is if I were the tile guy and I wanted to make my life easier!
From contributor Y:
Quit whining and figure out how to work together and all will be well.
The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).
Comment from contributor L:
I like flooring to run under cabinets, as it keeps water damage to a minimum. If I can't do that, I use a built up pad of plywood that I either paint or cover with scrap vinyl. This way, when the flooring is installed, it isn't higher than the cabinet openings for the dishwasher.
I like to run tile under jambs so the cuts are hidden and the job looks better. I use a color matched sanded caulk to bridge any discrepancies. I would do base and/or shoe after tile or hold the base up and just do shoe last to make sure there is a proper expansion joint left for the tile/slate.
Comment from contributor C:
I'm a tile setter/owner with employees in Orlando, Fl. During the early years I have learned that there are several ways and styles that subs do work. It is very important that they work well with each other, i.e. plumber with tiling shower, countertop with backsplash, trim with floor, etc. In new home construction I prefer that the door jams already be set in place, then trimmed by my guys to proper height for a smooth finish. Also, this allows for the carpet transitions to be placed in the center of the door, so you do not see the carpet or tile when the door is shut. Then the base molding would come after the tiles are run up to the wall. If the trim guy has to install prior to the floor being tiled, putting a 1/2 inch scrap sheet rock under the base will give the tile guy plenty of room to work. More than likely, the trim guy or punch out person will have to caulk later between the tile and trim, due to slab imperfections that are not caught. The trick is to allow the subs to converse prior to installation if they have never worked together. A good tile setter does not need shoe molding to cover mistakes, in most cases.
Comment from contributor B:
We are tile setters who set tile before or after cabinets. Some customers want their tile set before cabinets because, when set after cabinets, the grout line between the tile and the cabinet toe kick usually cracks because of the expansion and contraction of the wood, which soon breaks up the grout. As for the the door jams, no problem either way, and baseboard should be set after. After all, isn't that one purpose of the baseboard to cover the cut edge of any floorcovering and the sheetrock? We have found that working with the trim guys in this way is workable.
Comment from contributor N:
I trained as a tilesetter for three years with a group of union tilesetters with around 300 years of experience between them. I have since worked for myself setting tile for eight years. If I had my preference, I'd set the tile on a mud floor while the drywallers were taping and mudding, if space allowed. Otherwise, I'd like to set my subfloor and tile right after.
Doesn't always work out that way, though, and as a professional, I will do what I have to to insure a proper installation. This does take longer and is a lot more work, so I charge more for cutting jambs and so forth. If your base is already down, I'll r/r it and charge the contractor.
As for all the trim carpenters' complaints, I assure you that it is easier to cut wood to tile (if tile is done correctly) than vice versa. Cabinets should go over tile in case of changes made later, remodels, etc. The biggest problem for all of us who have taken the proper steps to master our trade is the incompotent contractor who tries to cut corners.
Comment from contributor O:
All flooring is last except stained concrete, period! What is the difference between a finish carpenter cutting a jam to an unlevel floor or because the GC didn't allow for finish floor in his R/O for head height? I just finished a job where the super had prefinished hardwood put in with a full on leak before drywall, worked out great for us cause we could base over before hardware, but I'm sure when it buckles, we will be doing a change order. Cabinets first, also. Learn how to cut, layout, and do quality work, or go home.
Comment from contributor D:
The tile guy should go first. If this is not possible, then the trim carpenter should run base everywhere except the area to be tiled. Then after tile is layed, you can get the base nice and tight to the tile, and you don't have the tile guy prying or cutting at the base.
Comment from contributor H:
We are a GC who does full remodel from start to finish without plumbing, electric, etc. We always tile first - under cabinets. If there is a leak, the tile will protect subfloor and if there is a change in the future, it doesn't screw the next homeowner. We then set our trim. Cover floor and there is no problem - set tile flat and there is no problem.
Comment from contributor R:
This is a very interesting subject with many outcomes depending on your geographical area. As a professional tile setter for 37 years and an accomplished trim carpenter I can understand both sides of this issue. I personally feel the door jams should be installed first.
With the wood available nowadays it warps quite easily. This makes it very difficult to plumb a jamb let alone notch it to tile for a professional result. I do agree mud should be pulled first to establish a level plane with cabinets installed and tile last. With the tile cut to the cabinets this eliminates the need to secure the base to the floor. Almost all of my installations are diagonal, which makes it very time consuming around crooked walls so I have the base and shoe installed last. If I'm asked my preference this is the way I like it, but most of the time all trim carpentry is completed before I arrive on the job.
Comment from contributor I:
Make sure to coordinate with the floor layer on the elevation they would like the jambs at. If the flooring is vinyl/sheet flooring the flooring is done first. The worst case is setting the jambs on the sub-floor, then having to cut 3/4" off and realizing that the door rubs on the carpet after. Then the door has to be cut down too. Coordination with the sub-trades is a must if you want the job to run smoothly.
Comment from contributor W:
When you set a door, you might need to raise one side of the jamb to make the top gap the same across. If you set the door first, you can cut the jamb the exact fit and it is a whole lot easier to use a jamb saw than to pull the whole door down and cut one side of the jamb.
Comment from contributor A:
I'm a tiler and to me this issue is simple. If the trim's down and creates more work for the tile man (longer hours on the job) it's reflected in the final billing. Do the extra work in a good and acceptable fashion, and bill reasonably for it. Ensure there's a descriptive clause in the contract before anybody signs. It's a reasonable option that allows the GC to plan his/her jobsite choreography in a realistic manner.
Comment from contributor E:
Floors have to be replaced more often than trim. If you sit all your trim on the floors and have to replace the floors then you have to at least remove most of the trim if not replace it. Base was originally intended just to cover the 1/2" crack from slab to sheetrock. If you are going to cover that up with your floor you don't even need base. Shoe mold is 1/2" X 3/4" and if the floor guys can't get within 1/2" you can always lay the shoe down for 3/4" cover. Door jambs should be all that have to be jamb sawed. Doors don't always sit flat on the floor and are often of the ground as much as 3/4" on one side while the other sits on the floor to level the door.
Somebody stated it pretty simply in the beginning, "anybody that knows anything about construction knows the floors go in last. Especially with the fluctuations in wood flooring nowadays from 3/4" down to 3/8" (gees) what's next 1/4"-1/8"? These floors, even more than usual, will have to be replaced before the trim unless you can't get the flooring out without removing the trim. But then again, doing the floors first would be creating work and I am unemployed, so what do I know? Still, my vote is for the trim guys.
Comment from contributor B:
Cabinets/doors/base first! Doors should only be set first and held up no more than 1/2 under jamb where there is going to be carpet, because then the carpet can be tucked under jamb. Finished floors should be carefully protected whether by GC trim carpenters or floor installer. If an unfinished wood floor is installed the shoe would go down after the first coat of varnish or final coat. Undercuts never turn out good, especially when the flooring guy is mad he has to do it. If the undercut ends up being too high, then there’s going to be a bigger problem. Also tiling and grouting to cabinets is a bad idea for a lot of reasons. One the cabinets are wood and will expand and contract leaving gaps between cabs and flooring and grout will crack. A good finish carpenter can scribe cabs to floor up to a 1/4 inch any more than that which means there’s a floor problem that should of been taken care of first.
If it is too late there is no other choice than to shoe or some kind of moulding around cabs. Installing cabs before any flooring is bad. I too have had to do it but was not my choice and looked like crap when the flooring guy tried to make perfect cuts to the cabs, then i had to shoe it anyways.