Calculator
Reference values (where the math comes from)
| Wall material | Per-anchor capacity (M8) | HK example |
|---|---|---|
| Cast concrete > 30 N/mm² | 180-250 kg shear | 1968-2000 HK old-tower partitions |
| Brick + chemical anchor | 100-140 kg shear | HK 1950s-1970s walk-ups |
| Hollow drywall (in studs) | 30-50 kg shear | tenant-renovated rooms |
| Tile-on-tile | 15-25 kg shear (anchor in adhesive only) | 1980s bathroom-converted |
| Thin partition unknown | 5-15 kg shear | any tenant DIY |
| Freestanding variant | N/A — load to floor | any wall, including no wall |
Embed this calculator on your site
HK property bloggers / interior design firms / structural engineers welcome to embed this calculator on your site:
License CC-BY-4.0 — free use with attribution to "Wallbed by Design 窩居·家 (wallbed-hk.com)".
After the calculator says PASS — what's next?
If your wall passes the load check, the next gates before install are:
- Wall material verification on-site — magnet test (steel studs), tap test (hollow vs solid), 3 mm pilot probe (concrete vs gypsum vs tile). We do this free during consultation.
- Plumbing / electrical mapping — Bosch wall scanner to avoid hidden services at anchor positions.
- Floor levelness — laser-level check; >5mm tilt over 1.5m forces shimming or freestanding variant.
- Egress check — open bed must not block 1.2m HK fire-egress path.
- Building management approval — most HK IO don't restrict, but luxury developments (Parkview / Tregunter / Estoril Court) may have notice requirements.
FAQ
Does this calculator account for the human weight when the bed is open?
No — and intentionally. When a wall bed is open and occupied, human weight (~150 kg for two adults) transfers to the floor via the bed's foot legs, not the wall. The wall only sees the bed-unit dead load (~127 kg standard Queen). This is the part most non-engineers get wrong.
Why are HK 1968-era walls strong enough for modern furniture?
HK 1968-era residential concrete was specified at 30 N/mm² minimum (Code of Practice for Concrete 1969, the predecessor of the current 2013 code). That's structurally sound for any modern furniture load including wall beds. Concerns are warranted only when wall material is unknown — drywall, tile-on-tile, or thin tenant-installed partitions.
What if my calculator output says FAIL?
Two paths: (1) increase anchor count or use chemical anchors instead of expansion. (2) switch to freestanding variant (zero wall anchors, ~12% upcharge). For HK old buildings with unknown wall material, freestanding is the safe default.
Is this calculator usable for HK Buildings Department submission?
No — wall bed installation is non-structural alteration under Buildings (Construction) Regulations Cap. 123B and does not require BD submission. This calculator is for buyer / engineer / surveyor reference only.