As I promised in
this thread way back in August, I am finally posting pictures of how we modified a 36" IKEA sink base to hold an undermounted 36" Whitehaus Quatro Alcove fireclay farm sink.
This particular sink is 36" x 20" x 10" and weighs about 100 lbs (I think - seems heavier!). I intended to get the Domsjo sink base, but purchased the regular sink base instead, and it really made no difference in the end.
Because the sink is wider at the top than it is at the bottom, as an undermount, the only way it would fit into the 36" base was if the sides of the cabinet were cut down.
We carefully measured where the cut would be by placing the sink on the floor and holding the cabinet side up to it. In order to work as an undermount, the top edge of the sink should be flush with the top edge of the surrounding cabinets.
A Pictorial Tutorial - Modifying a sink base for non-IKEA apron front sink
A Pictorial Tutorial - Modifying a sink base for non-IKEA apron front sink
We made the cuts using a table saw.
A Pictorial Tutorial - Modifying a sink base for non-IKEA apron front sink
And assembled the cabinet.
A Pictorial Tutorial - Modifying a sink base for non-IKEA apron front sink
We added the top piece to the rear part of the cabinet only.
A Pictorial Tutorial - Modifying a sink base for non-IKEA apron front sink
Then we turned the cabinet upside down over the sink to double check the fit. Why did we do it this way? Because right now, there is nothing to support the sink. The sink tapers, remember, and is too narrow at the bottom to sit on the cabinet sides.
A Pictorial Tutorial - Modifying a sink base for non-IKEA apron front sink
Using 5/4" lumber (not regular 2x4s as it says in the photo description - I wish I could edit that), my husband built a support structure for the sink to sit on.
A Pictorial Tutorial - Modifying a sink base for non-IKEA apron front sink
The bottom piece of lumber is screwed to the cabinet side and then the cross braces were measured and cut to sit on top of that. The cross braces are also screwed into the sides of the cabinet. We spaced them so that they would not interfere with the drainhole and so they would adequately balance and support the weight of the sink.
A Pictorial Tutorial - Modifying a sink base for non-IKEA apron front sink
A Pictorial Tutorial - Modifying a sink base for non-IKEA apron front sink
We measured where the plumbing would go in the cabinet floor and cut the hole out with a circular saw. (It probably would've been easier had we done this before we assembled the cabinet.)
A Pictorial Tutorial - Modifying a sink base for non-IKEA apron front sink
Then we pushed the cabinet into place to make sure the plumbing fit and lifted the sink onto its supports. Would it hold?
A Pictorial Tutorial - Modifying a sink base for non-IKEA apron front sink
So far so good. We checked the placement of the sink side-to-side and also front-to-back to make sure the drainhole was clear and there was enough room behind the sink for the faucets and plumbing.
A Pictorial Tutorial - Modifying a sink base for non-IKEA apron front sink
We then measured and cut the holes for the electrical and dishwasher lines and nailed the back of the cabinet on. The finished modified sink base cabinet. Ta da!
A Pictorial Tutorial - Modifying a sink base for non-IKEA apron front sink
We lifted the cabinet up and over the plumbing and set it in place.
A Pictorial Tutorial - Modifying a sink base for non-IKEA apron front sink
A Pictorial Tutorial - Modifying a sink base for non-IKEA apron front sink
You'll notice there is a gap between the sink base and the adjacent cabinet. This is by design. We're using custom doors, and there will be a decorative half-post on either side of the sink base which will cover this gap. It was necessary in order to achieve symmetry and ensure that the cabinet was centered underneath the window. We later went back and put a piece of 1/2" plywood inside the gap for stability and to join the two cabinets together. We did the same thing on the other side with the dishwasher.
Finally, we lifted the sink into its final position and connected the plumbing.
A Pictorial Tutorial - Modifying a sink base for non-IKEA apron front sink
The sink and cabinets have been in use for several months now. We've installed Pronomen countertops with a negative reveal. The only problem we encountered?
One week after install, the right front little plastic leg exploded into a bunch of pieces like it had been smashed with a hammer. I suppose the weight of the sink and cabinet was too much, even though the legs are meant to hold a lot. It may be because there is no cabinet on this side (only a dishwasher) to help with stability, so that ended up being the weakest point. We removed both front legs (but left the back ones) and built a 2x4 support base for the cabinet which will eventually be covered with the plinth.
These photos can also be found in an album in the gallery. We modified the corner lazy susan cabinet and the cooktop cabinet as well (not pictured), and I will try to post pictures of those modifications too when I get the chance.
Hope this was helpful!
A Pictorial Tutorial - Modifying a sink base for non-IKEA apron front sink 
