To install an undermount farmhouse sink, you need three things to go right: a sink base cabinet sized and braced for the basin, a support system that holds the sink tight to the underside of a stone or solid-surface countertop, and a continuous bead of silicone that keeps water out of the seam. The usual order is simple. Have the sink on site before the countertop is templated, build the support, set the sink with sealant, let it cure for 24 hours, then connect the drain. Your stone fabricator or plumber usually handles the cutout and mounting, but knowing each step helps you plan and avoid leaks.
In this article
- What does an undermount farmhouse sink install involve?
- What cabinet does an undermount farmhouse sink need?
- How do you support a metal sink under the counter?
- Which countertops work with an undermount sink?
- How do you install it, step by step?
- How do you seal the sink so water stays out?
- FAQ
What does an undermount farmhouse sink install involve?
"Farmhouse sink" covers two styles. An apron-front sink has an exposed front panel that replaces part of the cabinet face. A rimmed undermount sink sits fully below the counter, with the stone edge running cleanly over its rim. We make both. Sinks like the Fes are the rimmed undermount kind, and we can make an apron-front farmhouse sink to order in copper, brass or German silver.
Either way, the sink is held against the underside of the counter, so it must be supported and sealed well. Here is how the work usually splits up.
| Stage | What happens | Who usually does it |
|---|---|---|
| Plan the cabinet | Measure the sink base, check plumbing room, decide on support | You, your cabinetmaker or contractor |
| Template the counter | Trace the actual sink for the cutout and faucet holes | Stone fabricator |
| Mount and seal | Fix clips or support, run silicone, set the sink | Fabricator or installer |
| Cure | Leave adhesive and sealant untouched for at least 24 hours | Everyone, by waiting |
| Connect | Fit the basket strainer, faucet and drain piping, test for leaks | Plumber |
What cabinet does an undermount farmhouse sink need?
Measure the inside width of the sink base cabinet, not just the door opening, and check the side walls are sturdy enough to carry support cleats.
- Size the sink to the cabinet. Our sink sizes are the inside of the basin, excluding the rim, so allow for the rim on top of that. For the Fes, the 30 and 33 in sizes fit most standard 33 to 36 in sink base cabinets.
- Leave room below. Deep basins need space underneath for the basket strainer, P-trap and any disposal, so check clearance before you choose depth.
- For an apron-front style, the cabinet face has to be cut or built to receive the apron, so a dedicated farmhouse sink base is often the cleaner route. Send us the cabinet width and we will size the apron to it.
Because each of our sinks is shaped by hand, measurements are approximate. Have the sink in hand, or at least confirmed dimensions from us, before anyone cuts stone or cabinetry. If you are still choosing, our post on 9 questions to ask before buying a copper or brass sink covers sizing and lead times.
Solid unlacquered copper, hand-hammered in Fes, in inside lengths from 24 to 36 in or a custom size. Brass basket strainer included.
How do you support a metal sink under the counter?
A full undermount sink hangs on its fixings alone. RONA's undermount installation guide lists clips with glue-on bases, a rail system, mounting brackets, a wood support frame or a plywood platform under the counter, and says the frame and fasteners should be able to support 300 lb.
- Clips anchored to the stone. The fabricator bonds anchors to the underside of the countertop and clamps the rim up against it.
- A wood support frame or cleats. Rails screwed to the inside of the cabinet carry the basin from below.
One rule matters more than the rest: sealant is not glue. As Ask the Builder puts it, caulk is not to be used as the adhesive. A sink held up by silicone alone can eventually drop into the cabinet.
Which countertops work with an undermount sink?
Undermount sinks need a countertop with a solid, water-resistant edge, because the cut edge of the counter is exposed above the basin. RONA notes that undermount sinks are not recommended for wood, laminate or ceramic tile countertops.
- Good fits: granite, marble, quartz and solid-surface tops.
- Poor fits: laminate, wood and tile.
The fabricator should polish the cutout edge and drill faucet holes in the counter, since undermount sinks do not carry a faucet deck of their own. Pick your faucet before templating so the holes land in the right place.
Hand-formed solid brass in 8 sizes, from a 16 x 12 in bar sink to a 45 x 20 in main sink. Brass basket strainer included.
How do you install it, step by step?
RONA and Ask the Builder both describe attaching the sink before the countertop is secured to the cabinets. The usual sequence:
- Get the sink on site first. Handmade sinks vary slightly, so the fabricator should template from your actual sink.
- Cut and polish the opening. RONA recommends asking a professional to cut countertop openings.
- Dry fit. Set the sink against the cutout and check the reveal (how much rim shows) is even all round.
- Prepare the surfaces. Clean the rim and the underside of the stone so they are dry and dust-free.
- Run the sealant. Lay a continuous bead of silicone around the top of the rim. RONA suggests a 1/8 in bead.
- Set and secure. Press the sink into place, then tighten clips or bring the support frame up snug.
- Clean the squeeze-out. Wipe away excess silicone inside the basin before it skins over.
- Wait. Allow at least 24 hours before using the sink or loading it.
- Connect the plumbing. Fit the basket strainer, faucet and drain, then run water and check for drips.
How do you seal the sink so water stays out?
The seal keeps water away from the cabinet. Use a clear silicone sealant rated for kitchens and suitable for both the stone and the metal. Ask your installer to confirm the product is compatible with copper or brass before they use it.
Once cured, wipe the seam with mild soap and water, dry the sink after use and skip bleach and abrasive pads, which are hard on both the sealant and the living finish. Our Care and Patina Guide covers the full routine for unlacquered copper and brass.
Solid brass strainer for standard 3-1/2 inch drain openings, with a slotted basket and center post stopper.
Still weighing the budget side? Read how much a copper farmhouse sink costs and what you are paying for.
Frequently asked questions
Can I install an undermount sink myself?
You can plan the cabinet, build support cleats and connect the drain yourself, but the countertop cutout and the clips bonded to the stone are usually done by the fabricator.
Does the sink go in before or after the countertop?
The sink is normally attached to the countertop before the top is secured to the cabinets. The fabricator still needs the sink on site first, so they can template the cutout from the real basin.
How long should silicone cure before I use the sink?
Plan on at least 24 hours before using the sink, loading it with dishes or hanging the drain piping from it.
Can I put an undermount sink in a laminate countertop?
It is not recommended. Laminate and wood have a core that can swell when the exposed cutout edge gets wet. Stone, quartz and solid-surface tops are the better match.
Do your sinks come with a drain?
Yes. Every Brass & Basin sink comes with a drain. On our undermount kitchen sinks, that is the 3-1/2 Inch Unlacquered Brass Kitchen Sink Basket Strainer, which fits standard 3-1/2 inch drain openings. The strainer is also sold on its own if you want a spare.
Find the sink your cabinet was made for
Handmade copper and brass sinks from Fes, including apron-front styles and custom sizes made to order.
Shop farmhouse sinks →Not sure about sizing? Send us your cabinet and cutout measurements and we will help you choose.