If the new baseboards are 3/4" thickness, they can install 3/4" quarter round on the top edge giving it a round over. It would be a full 1/4 radius. If your existing is only partially radiused, a 3/4" shoe moulding would come close or they could simply have a cabinet shop make some up to match your existing. Routering up what's already installed and doing the corners by hand would be a nightmare at this point. It can be done if they are competent, but moulding over on top would be your best bet.

"they can install 3/4" quarter round on the top edge giving it a round over"

If you go this route make sure you get real 3/4 inch quarter round.

A lot of quarter round is made using 3/4 inch stock, and ends up measuring 5/8.

I would add a 5/8" x 1 1/8" "base cap" or a simple 5/8 x 5/8" quarter-round creating a slight reveal (setback) and giving the baseboard a bit more architectural style and avoiding alignment issues. IMHO that would be a substantial upgrade and worth pushing for.

I wouldn't worry about the base matching in all rooms.

Here is a link that might be useful: base cap

Absolutely make sure everything matches, especially in the same room. It's so disappointing, when you have to look over someone's shoulder, just to get them to do the job they've agreed to do. Hope things work out well :)

"A lot of quarter round is made using 3/4 inch stock, and ends up measuring 5/8".

More often than not however I have run across some fingerjoint 3/4" quarter round that was 13/16" in width. Being paint grade, the o.p. can make it all one if it is 5/8" if the installer holds it flush to the outside. They can make it all appear as on piece of wood using caulk and filler if they are competent. I understand they, (the op), are doing the painting.

The 1/2 a$$ed home remodeler who spiffed up our bedroom went the cap over squared board look for the base trim. It looked awful. There is no way to hide the line where the 2 pieces meet.

As you felt a need to specify the type of trim in your contract, I'd suggest the builder take out what they installed and fix it properly.

I have to agree with jmc01. Calmly but firmly point to the contract and say, "That is not the baseboard we agreed to. You'll need to replace that with the material listed here."

The contractor will object. Just keep calmly repeating yourself, "The contract says the baseboard will match existing trim - it has to match."

That sentence is your reply to every question or objection. Examples you'll probably hear, "But it's primed & painted, we can't return the material now." "We can make it look the same by rounding the corners over." "That will cost more money."

If they want to TRY to round it over I would say, "You can try it on a section, but if I don't feel it matches well enough, I won't accept that as a solution that fulfills our contract."

Contractors want to act like your friends, buddies, etc - but they are businessmen and this is a business transaction. Never forget that. They don't need to like you to do good work, they just need to respect you & understand that you are being rational and calm.

"Match existing" is a risky specification especially if it is only noted on the drawings. If the existing base is a standard shape, a manufacturer and model number should be specified or a profile of it should be in the drawings. If it is not a standard shape, it should be made clear that a custom copy is to be fabricated. In any event, the specification should always require that samples of all trim be submitted for approval before installation.

The traditional way the joint between a base and a base cap is hidden is with a small reveal at the bottom of the cap. If a quarter-round is used it should be narrower than the top of the base. Quarter-round is usually made in 1/2", 5/8", 11/16", 3/4" & larger sizes.

"There is no way to hide the line where the 2 pieces meet".

Simply not true for a paint grade project if the finisher has experience. I've done it many times with no call backs. You are correct though with the attitude that it should be removed and installed as specified in the contract. That would be the right thing to do.

"In any event, the specification should always require that samples of all trim be submitted for approval before installation. "

Good way to drive up costs on a small job.

This is not a large commercial project.

Trying to fix it later is usually more expensive and unnecessarily stressful especially on small jobs.

Thank you all for your suggestions/advice! I talked to our contractor today who was not happy we called him out on it (to put it mildly...).

This is not a small project compared to his other projects he has done in the past - it is the norm. He doesn't do commercial work.

He said he can hand sand the edges to make them more rounded since ours aren't super rounded and the machine might round them too much.

He said if we wanted to "cap" them that it would be out of our pocket. Said that materials would cost too much.

I told him that the easiest solution to make them all match is okay by us. We just want them to "match existing" as it states in our contract.

We left the convo with him saying he wants to "try hand sanding" - not sure where he will go if that doesn't work out!

Another question - should we be able to see the break in the baseboards between the new and old or should he be able to sand/caulk them enough so that it isn't noticeable (at least from across the room)? They also had a visible line where the new crown molding (all new) was installed and they had a break in the pieces of wood. Is this acceptable? I'm starting to think that since it is the end of the project that he is cutting corners... :(

Exactly how rounded over are the existing baseboards? A picture would be nice but even trying to round over a clean edge, even when it's a small radius by hand sanding...good luck especially if it's primered/painted. I can't speak for the cutting corners aspect, but it sounds like he is trying to save a buck by doing the finish carpentry themselves rather than relying on subbing out to a reputable pro. Just because he's a builder doesn't mean he is qualified for any specific trade hands on. It's all about his experience. Any trims that have butt, mitered, coped joints should not be seen, especially when painted. A good finish carpenter can accomplish that.

The problem with adding a molding on top is that the more flexible half round tends to follow undulations in the wall more than the baseboards, so, unless this is added expertly, it can look bad where the two pieces of molding meet since the half-round may be "setback" a little more in some places than others, especially if its thickness is a close match to the baseboard thickness.

If you can't get him to agree to replace all the new boards, then I'd have him replace the old baseboards in the addition to match the new ones. There should be no argument from him on that and it won't be that expensive.
True, the baseboards won't match the 'older' rooms that have rounded edges, but once it's all finished and you have furniture back in the rooms, I think it's something you'll rarely notice.

Regarding the joints/seams, hopefully he isn't doing butt joints! They should be cut on an angle and overlapped. I would demand that he do it right and if he can't then he should bring in someone that can.