Not sure if you like this look, but our tiler didn't charge more for a 'brick' laying pattern. This adds a little more visual interest than standard, but saves you the money of the 45 degree tiling.

our laundry room floor (20x20 tile)

We had a simuliar problem that the tiler wanted more for both the 20" since 18" was in the bid plus dianginal. Our builder was able to negotiate with him that because of the amount of tiling we were doing (3000 sq ft alone) that it was in his best interest not to cause an up charge. Can your builder help you to reduce the charges at all?

If it is a big area, definately don't go down to 13". It makes it look really busy with the grout lines. If it was me, I would look to reduce in other areas that you can upgrade later.

Cursive, I've been battling similar decisions ever since electrical. For me it's the cabinets. I don't have an option to be "over budget", so I've decided to scrimp on some the finish items that are easy to change, and that homeowners are more likely to replace later. I decided to go with builder's grade outlet covers (50 cents each vs. $10 each. More than 100 outlets in the house), to downgrade my electrical fixtures in most rooms, to go with laminate instead of granite counters, to put vinyl on my service stairs instead of rubber treads, etc. These are choices that I can easily change in the future with any extra cash. (hahaha, I know...). I guess the real question for yourself is how much would your dream tile put you over? Is there an alternative tile that would let you have the look you wanted for less? I would go with it because it seems like tile would be difficult to change.

I wonder why he would charge more for laying fewer tiles over the same square footage? I would think that it would either be the same or less...?

I am getting the 20x20 tile thats normally 2.95 for 1.65 because my fiance's cousin has a tile company. But they don't do installation. My builder budgeted 5.00sf for install, but to do the bigger tiles on a diagonal its going to cost 7.50sf. It would be a 2 thousand dollar difference. I've already paid for my lighting and my granite, so I cant swap down. Could I do without gutters for a year or so?

I cant find my floor plan layout picture, but basicly its all one big room for dining/living/kitchen and then a long hallway. Would you use the 20x20 in the great room and then switch to 13x13 brick-lay down the hallway of the same color tile? Or would that be too much of a change?

I've been told that the larger tiles are more difficult to work with (heavier, awkward to square properly, etc). I think I see validity in that, but I'm not so sure that the extra cost is actually in proportion. OTOH, I've laid various sizes up to 15", and find that weight as well as size should be considered... squaring a couple hundred large tiles is exhausting in comparison to working with smaller, lighter pieces.

Laying a diagonal pattern requires a great deal of cutting for the edge pieces, otherwise it's no more difficult than any other tiling. Your higher cost should be for the extra tiles required and the labor to cut, but not for any actual difficulty in laying. You might want to consider just how the tiles fit at the edge -- halving is much less work with fewer tiles than are those edges which require an odd portion of each tile. And the fewer cuts required also decrease the potential for breakage [ruined tiles]. However, unless the tiler is very skillful, it's easier to ruin a whole tile when halving.

Having looked at MANY homes during our build, I would do the 20x20 on the diagonal and try to cut back someplace else.