November 9, 2025

5 Mistakes to Avoid for a Smooth Bathtub-to-Shower Conversion in Dover, NH

Swapping a tub for a shower seems straightforward until you open the walls. In Dover, older capes and colonials often hide surprises: plaster over lath, cast iron stacks, or joists that have seen a century of service. A well-planned bathtub-to-shower conversion can boost accessibility, save space, and modernize your bathroom. A rushed one can invite leaks, uneven tile, and costly callbacks. After managing and troubleshooting dozens of tub-to-shower conversions across Strafford County, these are the missteps that most often derail projects, along with practical ways to avoid them.

Mistake 1: Ignoring the structure and subfloor

The biggest hidden risk lives under your feet. Tub alcoves usually tolerate point loads differently than a full shower footprint. When converting a bathtub to a shower, you are changing how water interacts with the floor, and any deflection will show up as cracked grout, loose tile, or a failing pan.

Start by probing the subfloor around the old tub apron and the back corners where water tends to pool. In Dover’s pre-1970 homes, I often find 1x planks under a single layer of plywood, sometimes with moisture-stained edges. Joists might be 2x8s spanning longer than modern code likes. If the subfloor has soft spots or delamination, replace those sections. Sister any joists with notches from old plumbing. Aim for a flat, stiff substrate that meets modern deflection criteria before you set a shower base or tile pan.

If you are using a tileable shower pan, follow the manufacturer’s mortar bed or foam tray instructions exactly. Skipping thinset under a foam tray to “save time” is a shortcut that guarantees flex and hairline grout cracks within months.

Mistake 2: Reusing the tub drain location without checking slope and venting

Tubs forgive sloppy slopes. Showers do not. A tub trap can sit slightly out of level, and you may never notice. With a shower, the drain must meet the pan center or linear drain location, and the trap arm needs proper pitch to keep water moving. In Dover’s tight crawlspaces and slab-on-grade additions, I have seen conversions where the drain was shoehorned to “almost” center, leaving the pan flexing over an off-center void.

Take the time to realign the drain. For most 60-inch tub-to-shower conversions, you will either center the drain or install a linear drain at the back wall. Verify a consistent quarter-inch per foot slope on the trap arm and confirm the vent tie-in is legal and within distance limits. If you are upsizing from a 1.5-inch tub drain to a 2-inch shower drain, factor in the height of the trap and whether framing notches will be needed. When in doubt, a licensed plumber can re-run a short section in two to four hours, which costs far less than fixing chronic slow drainage or gurgling.

Mistake 3: Skimping on waterproofing details

Waterproofing failures rarely show up on day one. They show up after the first winter when humidity cycles and vibrations open up tiny gaps. The most common error I fix is mixing systems: cement board without a membrane in the field, a liquid-applied membrane in corners, and a generic drain. That patchwork leaves weak seams.

Pick a complete system and follow it. If you use a sheet membrane, run it continuously from the pan up the walls, overlap laps as specified, and use the manufacturer’s preformed corners and banding around niches. If you choose a liquid membrane, check the required wet-mil thickness and use a gauge; most DIY jobs end up at half the needed build. I have measured 8 to 10 mils where 20 to 25 were specified. That difference matters. Around mixing valves and showerheads, use sealable gaskets or properly layered flashing rings. The curb is another failure point. Ensure the membrane fully wraps over the curb and ties into the pan without staples or screws through the top.

Dover’s older exterior walls can be cold, which increases condensation risk. Insulate cavity walls behind the shower and, if you are using a vapor-retarding membrane, avoid creating a double vapor barrier by removing any existing poly behind cement board.

Mistake 4: Overlooking code, permits, and accessibility

Even a modest bathtub-to-shower conversion touches plumbing, sometimes electrical, and occasionally structural. Dover typically requires a plumbing permit for moving or upsizing drains, and an electrical permit if you are adding a new GFCI-protected circuit for lighting, a fan, or heated floors. Skipping permits can complicate resale; I have seen closings delayed when a buyer’s inspector flagged an unpermitted bathroom remodel.

Beyond code, think through long-term access. A 60-inch alcove allows comfortable movement, but if you install a bulky framed door and a tall curb, you have recreated the step-over problem you were trying to solve. If aging-in-place is a priority, aim for a 2-inch or lower curb, or a true curbless design if your joists and subfloor allow it. A 36-inch clear opening is a good target for most showers. Blocking behind tile for future grab bars costs little during construction and saves headaches later. A handheld shower on a slide bar at 36 to 48 inches high adds practical flexibility without compromising style.

Mistake 5: Choosing surfaces that do not match Dover’s water and climate

Dover’s municipal water is moderately hard. Hard water leaves mineral spots that make glossy black tile and clear glass look tired quickly. Porous stone in a daily-use shower demands sealers and more maintenance than most families expect. If you want low maintenance, consider large-format porcelain with a matte finish and minimal grout joints. Use a high-quality urethane or epoxy grout to resist staining. For glass, a factory-applied protective coating helps, but habits matter more. A quick squeegee after each shower keeps doors looking clean years longer.

Ventilation is another local factor. Winter air is dry, but bathrooms still need consistent moisture control. I recommend a quiet, Energy Star-rated fan sized at roughly 1 CFM per square foot of room area, with a boost mode or a 20-minute timer. Vent it outdoors, not into the attic. Many Dover capes have knee walls and short attic runs. Make sure the duct is insulated bathtub replacement installation tips and sealed to prevent condensation.

Planning the timeline and budget with realistic expectations

Most straightforward tub-to-shower conversions take 3 to 7 working days once materials are on site, plus cure time if you are using certain membranes or epoxies. If you are moving the drain, add a day. If you are going curbless and recessing the floor, plan for framing and subfloor work that can stretch to a week. Surprises like galvanized piping, hidden damage, or knob-and-tube wiring behind the wall will extend that timeline.

Material costs vary widely. An acrylic shower system with walls, base, and door can land between $2,500 and $5,000 in materials, with labor bringing the total to the mid four figures. A fully tiled shower with a quality drain system, porcelain tile, and glass typically runs higher, often into the low five figures depending on glass and tile choices. The cheapest option is not the least expensive if it fails early. Spend where it counts: waterproofing, drain components, and the shower enclosure.

A quick pre-demo checklist

  • Confirm drain size and location against your chosen pan or linear drain, and verify slope and vent distance.
  • Inspect and repair subfloor and joists; get the floor flat and stiff before waterproofing.
  • Commit to one waterproofing system with compatible drain, corners, and accessories.
  • Plan for ventilation, lighting, and blocking for future grab bars before closing the walls.
  • Pull the necessary permits and schedule inspections to avoid delays later.

When to DIY and when to call a pro

Plenty of homeowners in Dover successfully tackle parts of a tub-to-shower conversion: demolition, framing, insulation, even tile if they have patience and a steady hand. The inflection points for professional help are plumbing changes, curbless conversions that require structural modification, and waterproofing details where a small mistake can undo the entire project. If your home has cast iron drains, a floor system that needs reinforcement, or a complex glass enclosure, bringing in a licensed contractor can reduce risk and compress the schedule.

A thoughtful plan, a compatible set of materials, and respect for the hidden parts of the bathroom deliver a smooth outcome. Done well, a tub-to-shower conversion makes daily life easier, adds value, and fits the character of Dover homes without inviting callbacks or repairs.


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.