Bathrooms that suffer from poor (or no) ventilation might very well harbor mold and it’s not uncommon to demo your shower walls and find that your bathroom’s wood structure has succumbed to many years of wet, humid conditions.

While it’s important to choose your materials — shower, bath, toilet, sink, lights etc — before taking a sledgehammer to your dated ceramic floors, you’ll also need to work with your general contractor to determine what more structural upgrades need to get done to ensure that when you finally settle in for that long-awaited bath in your new freestanding tub, you can be confident that your subfloor is in good shape and can support its weight.

This guide will help you decipher the different steps of a bathroom renovation from potential costs to important things you need to take into consideration. We’ll use an average-sized 5x8 three-piece bathroom with combined shower/tub, toilet and single sink as our baseline. We’ll also assume that for this baseline, plumbing fixtures don’t move and all materials are in-stock from a big box or bathroom specialty retailer.