ud83dudcda Bathroom Renovation Series u2014 13 of 25
u2190 Bathroom Renovation Vol.12: Under-Floor Storage Pt.1 u00b7 Series Index u00b7 Bathroom Renovation Vol.14: Under-Floor Storage Pt.3 u2192
u270fufe0f Originally published: 2016-12-05 / ud83dudd04 Updated: May 8, 2026
2026 Update from DIY Dad: Under-Floor Storage & Ceiling Work in the Bathroom/Laundry Room
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Re-caulk every 3u20135 years. Black mold on caulk is the #1 tenant complaint in Japan.
The renovation is now in the second half. Under-floor storage and ceiling access hatch installation may seem like thankless work, but they’re critically important. More than ten years on as a landlord, DIY Dad is still glad these were done.
Why Install Under-Floor Storage?
Without under-floor access, the only option when inspection is needed is to pull up the flooring. In wet areas especially, the speed of response to plumbing problems is completely different when you have a hatch.
Benefits DIY Dad Has Experienced
- Annual visual inspection of pipes (early detection of termites and corrosion)
- Direct visual check of drain pipe joints (early leak detection)
- Ability to inspect the condition of moisture-barrier sheeting
- Doubles as usable storage space (preserved food, emergency supplies, etc.)
Under-Floor Storage Installation u2014 Step by Step
- Decide on placement (confirm it fits between existing floor joists).
- Cut the plywood and cushion floor to the opening size.
- Partially cut the floor joists and add reinforcement pieces.
- Drop the unit body in and secure it.
- Finish the lid by applying cushion floor material to it.
The critical step is reinforcing where the joists are cut. Cutting a joist reduces floor rigidity u2014 support pieces must be added at each end and screwed in. Skip this and the floor will flex.
ud83dudebf For Anyone Considering a Wet-Area Renovation
Vanity replacement is doable as DIY, but confirm drain pipe types and measurements before starting to avoid leaks.
Under-Floor Storage u2014 Cutting the Opening & Installing the Unit
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Hi, this is DIY Dad! Continuing the first-floor bathroom/laundry room renovation series.
The opening shape for the under-floor storage was marked out and starter holes were drilled. The jigsaw blade is inserted into these holes and the floor board u2014 and the floor joist u2014 are cut through. The opening is made.
u2191 The opening for the under-floor storage unit.
Reinforcing the Joist Frame
Since the under-floor storage box can be loaded with heavy items, the structure around the opening must bear that weight u2014 which bears on the joists surrounding the hatch. Reinforcement pieces are added to handle the load.
u2191 Joist reinforcement in progress.
All four corners are reinforced.
u2191 From a different angle.
Installing the Lid Support Frame and Storage Box
The lid support frame (u53d7u3051u67a0) is fitted into the opening.
u2191 Lid support frame in place, before gasket.
The gasket (sealing strip) is fitted onto the frame.
u2191 After gasket installation.
The storage box is dropped in.
u2191 The storage box installed u2014 it’s a good size with serious storage capacity! Pricing and specs are in the DIY Dad Equipment Guide u2014 Bathroom/Laundry Room Edition. That’s all for today u2014 see you next time!
ud83dudcda Bathroom Renovation Series u2014 13 of 25
u2190 Bathroom Renovation Vol.12: Under-Floor Storage Pt.1 u00b7 Series Index u00b7 Bathroom Renovation Vol.14: Under-Floor Storage Pt.3 u2192
DIY Renovation Quote Review Manual
How to read, compare, and negotiate contractor quotes. This manual saved me u00a5800,000 on a single renovation project.
ud83cudfe0 More from DIY Father
15 years of landlord experience u00b7 3 apartment buildings u00b7 DIY renovations that saved millions of yen. Browse all articles at diytosan.com
