Summary: As mentioned by @Venrez:
In addition, the ladders ‘glow’ like in this report, except toward the top, suggesting there’s multiple ladders further up. Unfortunately, my ladders were only two tall, so I can’t say what would happen with even longer ladders.
Steps to reproduce: Not too sure, as it didn’t happen with the first house I built, just with the few smaller houses I built after.
Versions and mods: No mods, latest release version in Steam at the time of writing, version 0.1.0 (release 122) according to the title screen.
OS: Windows 8 Pro 64 bits (6.2, build 9200)
Processor: Intel® Core™ i5-3450 CPU @ 3.10GHz (4 CPUs), ~3.5GHz
Memory: 8192MB RAM
DirectX-version: DirectX 11
Graphics card: NVIDIA GeForce GTX 660