November 9, 2025

Converting a Bathtub to a Shower in Dover, NH: 5 Common Mistakes and How to Prevent Them

Swapping a tub for a shower is one of the most useful upgrades you can make in a Dover home. It frees up floor space in narrow bathrooms, simplifies cleaning, and improves accessibility for aging in place. I have managed dozens of tub-to-shower conversions in older New England houses, including post-war ranches and early 1900s capes, and the same pitfalls appear again and again. Dover’s mix of older plumbing, tight framing, and chilly winters adds a few wrinkles that homeowners don’t always anticipate. If you are considering converting a bathtub to a shower, here are the five mistakes I see most often, with straightforward ways to avoid them.

Mistake 1: Ignoring Drain Size and Slope

Most tubs are plumbed with a 1.5-inch drain, while showers in New Hampshire typically need a 2-inch drain under current plumbing codes to handle higher flow. I have seen beautiful new tile showers stall during inspection because the drain size was never upgraded. Another overlooked detail is the slope to the waste line. Older Dover homes often have cast iron stacks and long runs with minimal pitch. A shower will expose sluggish drainage that a tub could hide.

The fix is simple on paper and tricky in practice. Plan to upsize to a 2-inch drain and confirm you can achieve at least 1/4 inch per foot of slope from the shower to the tie-in. If the joist bays run the wrong direction or the run is long, be prepared for options like notching within code, recessed how to replace a bathtub subfloors, or a low-profile drain assembly. In several 1950s ranches near Back River Road, we had to open the ceiling below to rework the line. It added a day, but it saved months of frustration later.

Mistake 2: Underestimating Moisture Management

A tub surround is forgiving. A shower is not. Water will find pinholes and seams. I have pulled out showers less than three years old because greenboard was used behind tile with no membrane. Dover’s winters also push warm, moist air toward cold exterior walls, which can condense behind tile if you miss the details.

Commit to a waterproofing system, not just “water-resistant” materials. Cement board is fine, but it needs a continuous membrane over it, either a sheet system or a liquid-applied product with proper mil thickness. For tiled pans, use a factory-made shower base or a full system pan and liner from a reputable brand. If you prefer a curbless look, plan the recess during framing and waterproof the entire wet zone, including the first few feet beyond the glass line. Ventilation matters too. An undersized fan will leave the shower damp for hours, inviting mold. Look for a fan rated at least 80–110 CFM for a typical bath and vent it outdoors, not into the attic.

Mistake 3: Skipping Structural and Height Checks

Tubs often hide uneven floors and marginal framing. When you remove the tub, you might find a patchwork of subflooring and a center joist notched for the old drain. A standard shower pan expects a flat, level base, and tile tolerates even less. I have seen homeowners troubleshoot a “rocking” acrylic base with shims, only to hear creaks and feel flex after a week.

Before placing the new pan, correct the subfloor. Replace water-damaged plywood, add blocking, and use a mortar bed or manufacturer-recommended foam support under acrylic or composite bases. If you are aiming for a low or no curb, verify joist depth, spans, and deflection. Many Dover capes have 2x8 joists with long runs, which can bounce. Tile and large format porcelain demand a stiffer assembly, often L/720 for stone and L/360 for porcelain. A quick deflection check and a layer of 3/4-inch plywood, sometimes topped with 1/2-inch underlayment, can make the difference between a shower that stays tight and one that cracks grout lines within a season.

Mistake 4: Misplacing Valves, Niches, and Glass

Function lives in the details. A shower valve set too high will splash cold water in your face every morning. A niche on an exterior wall turns into a cold spot and a condensation trap mid-winter. Glass sized without measuring finished dimensions will arrive wrong, and reorders can add weeks.

Think through use and the sequence of finishes. I like valves around 44–48 inches to the handle center for most users, with the shower head at 78–84 inches depending on ceiling height. In multi-user homes or for aging in place, consider a secondary hand shower on a slide bar with a diverter, mounted low enough for seated use. Place niches on interior walls whenever possible, and slope the bottoms slightly toward the shower. If you must use an exterior wall, add exterior insulation behind the niche or use a pre-formed insulated insert. For glass, do not finalize measurements until tile is complete. A 1/8-inch grout build can change everything.

Mistake 5: Overlooking Permits and Lead-Safe Practices

Even if you are comfortable tackling parts of a tub-to-shower conversion, Dover’s permitting process exists to protect you and future buyers. Plumbing changes, electrical work for a new fan or light, and structural modifications require permits and inspections. On pre-1978 homes, disturbing painted surfaces triggers lead-safe rules. I have walked into projects where a previous owner dry-cut old tile and trim, leaving dust that tested high for lead. Cleanup cost more than the shower.

Call the city’s Building and Licensing office before you start. Budget time for rough and final inspections. If your home predates 1978, hire an EPA RRP-certified contractor for any demolition that may disturb painted surfaces. For rework in tight bathrooms, a licensed electrician can help with GFCI protection, fan sizing, and switch placement to meet code and improve safety.

Material Choices That Respect New England Living

Dover’s water is generally moderate in hardness, but many homes still see mineral spotting on glass and fixtures. Frameless glass looks clean, yet it shows water marks more readily. A quality protective coating helps. For walls, large-format porcelain tiles reduce grout maintenance. If you want the fastest path, an acrylic or solid-surface surround with integral shelves and a matching base installs in one to two days and handles daily use well. For a midrange build, composite stone bases paired with porcelain walls strike a good balance of feel and durability.

If you are converting a bathtub to a shower for accessibility, a low-threshold base with textured surface, a 36-inch clear opening, blocking for future grab bars, and a thermostatic valve create a safer, calmer experience. I often add a fold-down teak or phenolic seat for those who prefer seated showering without committing to a fixed bench.

Budget, Timeline, and Dover-Specific Realities

Costs vary widely based on scope and finishes. A straightforward bathtub-to-shower conversion with an acrylic system, upgraded drain, and new valve commonly lands in the 6,500 to 10,000 range in the Seacoast area. Tile with custom glass, recessed lighting, and waterproofing upgrades can reach 12,000 to 20,000 or more. Lead-safe containment, cast iron stack modifications, or joist reframing add time and cost. Most tub-to-shower conversions take three to seven working days, assuming inspections are timely and materials are on site.

Season also plays a role. In winter, adhesives and mortars need temperature control, and exterior vent terminations for fans become trickier. If you are scheduling work in January, budget for a day to stage heat and keep materials within spec.

A Short Planning Checklist

  • Confirm drain upgrade to 2 inches and verify slope to the tie-in.
  • Choose a full waterproofing system for walls and pan, and size the exhaust fan properly.
  • Level and reinforce subfloor, and verify deflection for tile choices.
  • Set ergonomic heights, avoid exterior-wall niches when possible, and measure glass after tile.
  • Pull permits, plan inspections, and follow lead-safe practices in pre-1978 homes.

When a Tub Still Makes Sense

Not every home should lose its only tub. For buyers with young children or pet owners, a single tub can still be valuable. If you have two baths, converting one to a shower and keeping a tub elsewhere preserves resale flexibility. In smaller one-bath homes, I often recommend a deeper soaking tub with a glass panel as a compromise, especially when space or budget makes a curbless shower unrealistic.

Tub-to-shower conversions offer big daily quality-of-life gains, but they reward careful planning. Respect the drain, the waterproofing, the structure, the ergonomics, and the rules. Do that, and your new shower will feel solid underfoot, shed water the way it should, and look as good in five winters as it does on day one.


Jeff Coleman has been serving home owners in various roles over the last 25 years. In 2020 Jeff started Cloud 9 Tubs LLC due to his frustration with the sales tactics and poor customer service he experienced working for larger companies. He also has a passion for bathroom safety as most falls in the home happen in the bathroom and his own grandmother passed after experiencing a fall. His focus is not just on updating bathrooms but in providing a safer and more accessible bathing experience and creating a better quality of life for his customers. Cloud 9 Tubs LCC stands apart from their competitors in the emphasis that they put on the customer experience. Jeff takes great pride in the personal service that he and his team provide.