November 9, 2025

5 Costly Bathtub-to-Shower Conversion Mistakes Dover, NH Residents Should Avoid

Swapping a tub for a shower sounds simple on paper. In practice, a bathtub-to-shower conversion reshapes plumbing, waterproofing, ventilation, and resale dynamics. In Dover’s older housing stock, from mid-century colonials to 19th-century capes, surprises lurk behind tile and plaster. I have seen conversions go smooth as a weekend hike, and I have seen them snowball into structural repairs and insurance calls. The difference usually comes down to planning and discipline.

Below are the five mistakes that trip homeowners most often, why they matter in Dover, and how to avoid them.

Mistake 1: Ignoring Drain Size, Slope, and Venting

Many tubs run on a 1.5-inch drain. Most modern shower codes, including what inspectors in Strafford County expect, call for a 2-inch drain to handle higher flow and reduce clog risk. That change is not just a swap of fittings. It may require opening the subfloor, rerouting the trap, and verifying that the line has adequate slope and ventilation.

I once opened a tight alcove in a Garrison near Central Ave to find a 1.5-inch galvanized line tied to a tired vent stack. The homeowner had already ordered a rainfall showerhead rated at 2.5 gpm. Left as-is, they would have had frequent backups and a gurgling sink down the line. We replaced the trap and ran a 2-inch ABS line to the main, adjusting the slope to about 1/4 inch per foot and tying into a proper vent. That extra work prevented a routine service call every three months.

The tell: if your tub drain sits off-center and you plan a linear drain at the far wall, expect more framing, more plumbing, and a permit review. Build that into the plan and budget before tile ever ships.

Mistake 2: Skimping on Waterproofing Beyond the Wet Area

Tile is not waterproof. Grout is porous. The shower stays leak-free only if the substrate is waterproofed continuously and correctly. In Dover’s older homes, plaster and pine sheathing sit directly behind many bathroom walls. One pinhole, one missed seam, and moisture migrates into cavities, finds cold surfaces during winter, and condenses. By spring, you have swollen baseboards, a musty smell, and staining on the ceiling below.

I recommend a full-system approach: a cement backer or foam board approved for showers, seams taped and embedded, then a continuous waterproofing membrane, either sheet or liquid-applied to manufacturer mil-spec thickness. Tie the walls into the pan or receptor with a compatible flange or bonding flange drain. On remodels where we keep an exterior wall, I avoid poly behind the board if using a surface membrane to prevent moisture sandwiches. It best bathtub replacement options sounds fussy, but this is where most tub-to-shower conversions fail.

If you are converting a bathtub to a shower on a second floor, treat the floor like a wet room right outside the enclosure threshold. A two-foot apron of waterproofing under the bath mat area pays for itself the first time someone steps out with the water running.

Mistake 3: Choosing the Wrong Pan or Tile for the Subfloor You Have

Prefabricated receptors look appealing, and they can work well. But they demand a flat, level substrate. Old Dover floors often pitch, sometimes a half inch over four feet. Drop a rigid acrylic or composite pan on that and you will feel flex, hear creaks, or see the drain weep. Mortar bedding can correct a little, not a lot.

Tiled pans are more forgiving in terms of leveling, but they require skill. The preslope must be even to the drain, the liner or bonded membrane must be continuous up the walls, and the weep holes must remain open. I have replaced at least a dozen shower floors where heavy pebble tile soaked up water and overwhelmed an undersized drain in homes on older septic systems. Looks great on Pinterest, not great for long-term maintenance here.

A practical route for many Dover homes: use a foam shower tray that can be trimmed to correct out-of-square alcoves, then skim the subfloor with a self-leveling compound before setting it. Or, if the floor is truly out, have a carpenter sister the joists or plane the subfloor before any plumbing touches it. The right choice depends on your structure, not the showroom sample.

Mistake 4: Underestimating Ventilation and Humidity Control

A tub with a curtain leaks steam into the room slowly. A new glass-enclosed shower keeps moisture concentrated, then dumps it out when the door opens. If your fan is a tired 50 cfm unit tied to a long, sagging flex duct, you are courting mold on the window sash and paint that peels in sheets.

Aim for a quiet 80 to 110 cfm fan, sized to the room volume, on a humidity-sensing or timer switch that runs at least 20 minutes after a shower. In older capes, I often reroute ducting to a dedicated roof cap, not a soffit, to prevent moisture from drifting back into the attic. Check that insulation is intact around the duct and that the attic has proper baffles. In winter, this matters even more. Warm moist air meeting a cold roof deck is a recipe for frost and attic staining.

Mistake 5: Forgetting Accessibility, Clearances, and Resale

People convert tubs for many reasons, safety foremost. A well-built tub-to-shower conversion should make the space easier to use for decades, not just prettier. That means a curb no higher than needed, grab bar blocking in the walls even if you do not install bars today, and a shower valve that is easy to reach without stepping under the water.

Think through daily routines. If the toilet sits close to the new glass, can you still turn and sit comfortably? If the bathroom is narrow, a sliding door may beat a swinging panel. Consider a 36-inch minimum clear opening where possible and a handheld on a slide bar set around 42 to 48 inches. These choices help aging-in-place buyers and do not scare off families who still want a tub in at least one bathroom. If your home has two baths, keep one traditional tub for resale balance and do the tub-to-shower conversion in the primary or guest bath that gets the most daily use.

Dover-Specific Quirks Worth Planning Around

Many local homes have cast iron stacks and mixed-era copper and PVC drains. Cutting and adapting to a clean 2-inch line can take a few extra hours and specialty couplings. Floor framing often includes true 2x8s on wider spans, which can flex. I have measured deflection on some second-floor baths that made large-format tile risky. In those cases, smaller tile or a rigid receptor keeps grout lines from cracking.

Water quality also factors in. Dover’s municipal water is generally fine, but if your house has a private well in surrounding towns, mineral content can etch certain glass coatings and stain grout faster. Plan for a squeegee, a softener if warranted, and sealed grout. Small habits beat big cleanups.

Budgeting the Right Way

Sticker shock happens when the scope balloons midstream. A realistic range for a quality bathtub-to-shower conversion in Dover usually lands between $8,500 and $18,000, depending on plumbing moves, finishes, and whether we find rot. Moving the drain to center, adding blocking, upgrading the fan, and doing true waterproofing are not extras. They are the project. Finish choices swing the number: porcelain tile with a foam tray and semi-frameless glass costs less than hand-made tile and custom glass, but both can be durable if installed correctly.

If a contractor quotes a rock-bottom price, ask what is excluded. Permits, demo haul-away, substrate repair, and glass can hide off the initial sheet. Good bids spell out materials, methods, and inspection steps.

Permits, Inspections, and Peace of Mind

Dover requires permits for plumbing alterations and most structural or electrical changes. Skip the permit and you risk trouble during resale or an insurance claim. An inspector is not an enemy; a second set of eyes catches issues before tile goes up. The cleanest projects I have seen move briskly because the contractor kept the city looped in, scheduled inspections early, and documented waterproofing with photos.

Quick Pre-Project Checklist

  • Verify drain size, trap location, and venting path before ordering fixtures.
  • Test subfloor level and deflection, then choose pan or tile accordingly.
  • Commit to a complete waterproofing system, not a patchwork.
  • Upgrade or reroute the exhaust fan to a dedicated exterior termination.
  • Add blocking for future grab bars and confirm door and fixture clearances.

When a Conversion Is Not the Right Move

If the only bathroom in the house currently has a tub, think carefully. Families with young kids often want at least one tub. In a one-bath home, a sleek shower can narrow your buyer pool. Another pause point: severely undersized bathrooms. If keeping required clearances means a cramped shower that pinches at the elbows, a deeper tub with a low entry might actually be safer and more comfortable. Good design respects the limits of the room.

The Payoff for Doing It Right

A well-executed tub-to-shower conversion adds daily comfort, safer footing, and easy maintenance. The space feels bigger. Hot water lasts longer. With thoughtful choices and local know-how, you avoid the hidden costs that sink projects: undersized drains, soft subfloors, wet walls, and fogged glass. Dover homes have character, and with careful planning, your new shower will match it, not fight it.

If you take one idea from this: slow down at the start. Map the drains, evaluate the floor, plan the ventilation, and then choose finishes. That order keeps the project on track and protects your investment for years to come.


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.