Bathroom Renovation - 10 Mistakes That Cost a Fortune

Why Do Most Bathroom Renovations Exceed Budget?

Statistics are relentless - over 70% of bathroom renovations cost more than initially assumed. The main reason is not finishing materials, but mistakes in water and sewage installations, which only come to light after completion of work.

After 35 years working in the installation industry, we have seen hundreds of cases of costly corrections. In this article, we share knowledge that will help you avoid the most common pitfalls.

Mistake #1: Lack of Detailed Installation Design

Why Is This a Problem?

Many owners start renovation without a professional installation design, relying only on the contractor’s “experience”. This is a recipe for disaster.

Consequences:

Insufficient water pressure in faucets
Drainage problems (incorrect pipe slopes)
Collisions between installations
Correction costs: 650 - 1,700 EUR

SDI Solution:

We prepare a detailed installation design including:

Cold and hot water pipeline routes
Sewage system with slopes
Device connections (washing machine, dishwasher)
Mechanical ventilation

Mistake #2: Saving on Quality of Pipes and Connectors

The Truth About “Savings”

The difference between premium and budget pipes is 110-220 EUR. Cost of repairing a leak in the wall? 3,300 - 6,500 EUR (tile removal, repair, re-finishing).

For water installation:

Multi-layer pipes (e.g., Rehau, Uponor)
Pressed fittings (not threaded!)
Shut-off valves on each device

For sewage:

HT pipes with pressure certificate
Professional elbows 45° and 90°
Inspections in key places

Mistake #3: Incorrect Sewage Slopes

Most Common Amateur Mistake

Sewage pipe slope must be 2-3%. Too small slope = waste buildup. Too large = self-cleaning and odors.

How We Check at SDI:

Precise laser level measurement
Photographic documentation before closing the installation
Hydraulic tests before finishing

Problem Signals:

Slow water drainage
Gurgling in siphons
Unpleasant odors
Repair cost: 1,100 - 2,600 EUR

Mistake #4: Lack of Floor Waterproofing

Water and Gravity Don’t Forgive

A leaking bathroom floor is a time bomb. Water gets under tiles, causing mold, mildew and ceiling damage to neighbors.

Professional Waterproofing:

Waterproof membrane on entire surface
Sealing tapes in corners and passages
15-20 cm wall extension
Double layer in shower zone

Professional waterproofing cost: 330 - 650 EUR Repair cost after flooding: 4,400 - 11,000 EUR + compensation

Mistake #5: Poorly Selected Boiler or Instant Water Heater

Common Scenario:

Client installs 6 kW instant water heater, then complains that “barely warm water flows”. Problem? Power is insufficient for shower.

How We Select Devices:

Instant water heater:

Single point (sink): 3-4 kW
Shower: min. 9-12 kW
Shower + sink: 18-24 kW

Electric boiler:

1 person: 50-80 L
2-3 people: 100-120 L
4+ people: 140-200 L

Mistake #6: Inadequate Ventilation

Moisture = Mold = Health Problems

A bathroom without effective ventilation is an ideal environment for mold and fungi. Even 5 minutes of showering generates 1-2 liters of water vapor!

Solution:

Mechanical ventilation with humidity sensor:

Automatic activation at 60-70% humidity
Capacity: min. 100 m³/h for 6 m² bathroom
Quiet operation (max 30 dB)
Cost: 175 - 440 EUR

Signs of Poor Ventilation:

Steam settling on mirror after 10+ min
Moist walls
Black spots in corners

Mistake #7: Installing Shower Cabin Before Installation

Correct Order:

✅ Water and sewage installations
✅ Tightness tests
✅ Screed and waterproofing
✅ Tiles
✅ ONLY NOW shower cabin

Installing the cabin before tiles, you risk:

Leaks in connections
Cabin damage during tile laying
No possibility of replacing cabin in the future

Mistake #8: Ignoring Water Filtration

Szczecin Water Problem

In Szczecin and surroundings, water has hardness 200-350 mg CaCO₃/L, which means fast scaling:

Faucets and shower heads
Boilers and washing machine
Shower cabin

SDI Solutions:

Mechanical filter + softener:

Protects installation from scale
Extends device life by 50-100%
Better water quality for bathing
Cost: 550 - 1,100 EUR
Annual savings: 175 - 330 EUR (less detergents, no scale)

Mistake #9: No Emergency Shut-off Valve

”But I Have a Main Valve!”

Yes, but do you want to leave the entire apartment without water when replacing faucets? Professional installation requires:

Shut-off valves:

Before each faucet
Before washing machine
Before WC
Before boiler

Valve cost: 45-110 EUR Convenience: PRICELESS

Mistake #10: Choosing Contractor Based Only on Price

Cheapest Offer = Most Expensive Investment

After years of experience we see a pattern:

Client chooses cheapest offer (savings: 650 EUR)
Contractor “optimizes” (cheaper materials, simplifications)
After 6-12 months problems appear
Client pays 2-3 times more for repair

What to Look For:

✅ Experience - min. 10 years in industry ✅ Portfolio - completed projects with references ✅ Warranty - min. 5 years on installations ✅ Certificates - construction permits ✅ Insurance - liability insurance

Bathroom Renovation with SDI - Quality Guarantee

Why Did 500+ Clients in Szczecin Choose SDI?

✅ 35 years of experience in sanitary installations ✅ Full documentation - design and execution ✅ 5-year warranty on installations ✅ Premium materials - Grohe, Hansgrohe, Rehau ✅ Pre-finish tests - zero surprises ✅ Constant contact - project coordinator

Service Area:

Szczecin, Police, Stargard, Świnoujście, Gryfino, Goleniów - 150 km from Szczecin.

Free Quote and Consultation

Planning a bathroom renovation? Contact us:

📞 +48 513 166 235 📧 kontakt@sdi-instalacje.pl

We offer:

Free site visit
Quote broken down by materials and labor
Technical consultation
Help choosing materials

Article prepared by SDI sp. z o.o. team - sanitary installation specialists in West Pomeranian Voivodeship since 1987.