Kitchen and Bath Design: Fixture Design and Planning

In addition to the actual shape of the fixture and its installation concerns, mechanical requirements must be taken into consideration when planning a kitchen or bathroom.

Planning tips from kitchen pros

Bowl arrangement Unless your client is going to wash and rinse dishes in a double-sink configuration, demonstrate how a sink with one large compartment and one small compartment functions. This configuration gives you the largest sink for everyday use and a smaller—yet usable—compartment for other uses.

Corner sinks When placing a sink in a corner, do not push it back more than 2- or 3-inches away from the front edge of the countertop. That is the normal installation location, and it should be maintained (even in a custom design) so the client has comfortable access to the water source.

Damage Make sure your client realizes that cast iron, self-rimming sinks are susceptible to damaged edges or warping. This is particularly a problem with larger sinks. Inspect the sink before it goes to the jobsite. Look for chips along the lead edge. The client must accept the possibility of a wide caulking joint connecting the sink to the countertop for large sink configurations. With these self-rimming sinks, specify caulking that will match either the countertop or the sink so the joint compound does not become a focal point in the sink area.

Depth The deeper the sink, the straighter its sides. The tighter the angles where the sink side and bottom meet and the flatter the sink bottom, the bigger the interior space.

Food-waste disposer compartment Some sink configurations are a single size but have a small, round compartment for the food-waste disposer in one back corner. Because the compartment for the food-waste disposer is almost too small to use, this is not the most desirable sink configuration.

Holes Make sure you know how many holes are on the back ledge of the sink and how many holes you need for the faucet and water attachments. If a hot water dispenser, faucet, dishwasher air gap, other dispensers, and/or water treatment spouts are planned, you may run out of predrilled holes. Typically, cast iron sinks have four holes. A fifth hole can be drilled, but it is expensive and the sink may be damaged in the process. Adding extra holes is much easier in a stainless steel sink. In solid surface sinks, the holes are drilled in the countertop deck so the number and placement are flexible.

Overall size When specifying a solid surface integral sink, verify the overall dimensions of the sink. The literature may list the interior dimensions of the sink, not the overall dimensions. The overall dimensions will determine your spacing in a standard side-by-side double configuration. You may find it necessary to increase the cabinet size if you are planning to create a butterfly corner arrangement with such sinks.

Recycle center Some sinks have an opening within the sink that allows access to a chute for a compost container or a waste receptacle below.

Round shapes When specifying two round sinks as the primary sink arrangement, make sure your client understands the interior space of these sinks is less than a comparable square model. Recognize that these sinks require deck-mounted faucet locations; therefore, you must specify the faucet location on your plan.

Small sinks Avoid small, 12-by-12-inch sinks. They have a drain that does not accept a food waste disposer and are so small there will be a water-splash problem when the homeowner uses the sink for food preparation.

Strainer If you are not ordering a food-waste disposer to be mounted on the sink, make sure you order a good-quality strainer.

Under-mounted sinks If you use separate under-mounted sinks in place of a sink manufactured in a double configuration, warn your client that water will splash on the countertop if the faucet is swung from one sink to the other. Consider routing down the countertop section that separates the two sinks or recessing the entire configuration into the counter surfaces ¼-inch or so in order to eliminate the potential for water to run across the countertop and down to the floor.

Planning tips from bathroom pros

Integral bowls are the easiest to clean because of their seamless configuration. They are typically the shallowest type of bowls available, and a high-arched spout might cause a splash-back problem. A variety of pedestal lavatory sizes are available. The smallest pedestal lavatory is little more than a bowl on a base. Larger pedestal lavatories offer a generous bowl and counter space on each side of the lavatory. Plumbing specialists suggest you consider the following items when you specify a pedestal lavatory.

Open pedestal base The pedestal base may be open all the way down the back, may be solid up to 16 inches off a finished floor, or may have a horizontal support bar connecting both sides of the pedestal base somewhere along the back. These last two fixture designs may interfere with the drain location. Read the manufacturer’s specifications to verify where the drain line should be roughed in.

Finishing the pipes To maintain continuity, remember to consider the decorative finish on the shut-off valves, P trap, box flange, and supply lines as you select the other fittings in the bathroom.

Blocking in the wall If the pedestal lavatory does not completely support its own weight, the installation may require reinforcement behind the finished wall surface.

Vertically align the pedestal Because the plumbing lines are exposed behind the vertical pedestal base, it is critical the drain and supply lines are dimensionally balanced behind the pedestal. The rough-in dimensions must be perfectly centered on the pedestal.

Selecting the right faucet Choices of faucet-handle style and escutcheon-plate diameter may be limited if the pedestal lavatory has a small back deck or an integral splash along the back of the fixture. If you are specifying a fitting that has not been designed to fit on the pedestal lavatory by the fixture manufacturer, verify these two items are compatible by reviewing the dimensional information from both companies.

Specifying height The design of some pedestal lavatory bases limits the shut-off valves to about 16 inches off the finished floor. This height dimension is as important as the vertical arrangement just mentioned.

Countertop-mounted self-rimming lavatory

A lavatory designed to sit on top of the countertop is called self-rimming. If it does not have a finished edge, it will require a rim of stainless steel. The lavatory features a rim around the edge of the bowl that overlaps a cutout in the countertop. A bead of sealant is placed between the bowl rim and the countertop to prevent water seepage. The weight of the fixture, sealant, supply lines, and trap hold the lavatory in place.

Warpage Self-rimming lavatories are susceptible to warpage. Large lavatories, particularly oval designs, may not fit flush on the countertop. Because they do not rest perfectly on the countertop surface, they will require a larger caulking line.

Templates For some handmade china self-rimming bowls, no template will be available. In a bathroom with more than one lavatory, do not allow the installer to use one bowl to template all the lavatories—there may be slight differences. Each lavatory should be used for its own template in this unusual decorative situation. To prevent mistakes, make sure the self-rimming lavatory is on the job when the countertop is cut.

Ledge drilling The drilling location for a self-rimming lavatory must be verified before the cabinetry is ordered. Most standard self-rimming lavatories have one hole: a 4-inch center-set drilling or 8-to-12-inch widespread drilling as part of their back ledge. No special dimensioning is required because the overall depth of the lavatory will accommodate the bowl, overflow, and plumbing lines to the faucet.

Pay attention to the number and diameter of the holes drilled in the lavatory. A mini-widespread faucet does not use an escutcheon plate and has rigid piping, so there is no flexibility in the distance separating the valves from the spout. Therefore, if there is any discrepancy between the drilling holes on the lavatory and the faucet drilling, it will not work.

Another compatibility problem may occur when you attempt to specify a single-hole faucet with an escutcheon plate on a lavatory faucet that has been drilled with three holes. Sounds simple enough— you are going to use the escutcheon plate to cover the two unused holes. However, the diameter of the predrilled holes in the lavatory may not be suitable for a single-hole faucet. On many lavatories drilled for a standard 4-inch center set, the center hole will only be 1-1/8 inches in diameter. For a single-hole faucet, you will need a hole that is 1-¼ inches in diameter.

Vessel and above-counter bowls

Special planning concerns are involved in installing a sink that sits on or is partially recessed in the bathroom counter. These concerns involve the height of the user, the faucet location, and the relationship of the vessel bowl to the countertop.

Installation of vessel/above-counter sinks requires special planning. Check the overall depth of the vessel sink; it may require a deeper vanity than you are accustomed to specifying. 

Select the drain you will use; it may be more decorative than a typical drain and be ordered from a specialty house. 

Specify the faucet to match the vessel height. Elongated faucets are specifically designed for countertop installations with a vessel sink. Alternatively, wall-mounted bathroom lavatory faucets are available. The trajectory of the water flow from the faucet must be matched with the shape and configuration of the vessel bowl to make sure there is not excessive splashing on the user.

User height A vessel bowl placed atop a typical 32-to-36-inch-high vanity cabinet may be too high for a petite user and definitely is inappropriate in a children’s bathroom. Consider the physical height of the individual who will be using the vessel sink. If needed, partially recessing the vessel fixture may give you the look desired without added height.

Faucet location Not all plumbers are accustomed to vessel bowls— the craftsperson on the project needs to be aware the faucet positioning will be different for this type of special lavatory. A wall-mounted faucet needs to be positioned exactly by the designer for the craftsperson on the job. If a wall-mounted faucet is not being used, special decorative deck-mounted faucets that are installed adjacent to the vessel sink (not behind) need to be specified. 

Relationship of the vessel bowl to the countertop The designer must consider the material of the countertop, the material of the vessel bowl, and the waterproof caulking compound that will be used to join the two together. In many installations today, we see beautiful glass vessel bowls in glass countertops—once again, the finish and fit of all plumbing (now dramatically exposed) must be thought-through before the project is finalized—from a planning and budgeting standpoint.

Mounting methods for kitchen and bathrooms

Flush mounted The sink is recessed into the countertop substrate material so it is even with the counter material. This is particularly effective in a ceramic-tile top. Special sinks are designed that have square ledges so the sink sits on the countertop and can flush-out with the ceramic tile on the deck.

Integral The sink and countertop are all made out of one piece. This can be done with stainless steel or solid-surface materials. The opportunity to create a uniquely arranged sink configuration, the ability to specify an attached drain board, and the ease of maintenance are all advantages to this type of installation.

Rimmed The sink sits slightly above the countertop with the joint between the sink and the countertop concealed by a metal rim.

Self-rimming The sink sits on top of the countertop. A hole is cut in the surface and the fixture is dropped in by the installers. A bead of caulking is applied between the sink and countertop, forming a seal.

Under-mounted The sink is installed underneath the countertop. If you are under-mounting a cast iron sink, always order it with a glazed rim. PR
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This article is excerpted from the NKBA Professional Resource Library volume: Kitchen & Bath Products and Materials, Second Edition by Ellen Cheever, CMKBD, ASID, CAPS. To be published John Wiley & Sons, Inc. in November, 2014. Copyright National Kitchen & Bath Association.

Top tips to consider when planning a kitchen or bathroom.