Standards

A standard is a published number a design can cite. Every entry carries a source, and that is not decoration: the whole value of this validator is that it is not giving you opinions. When a report says a slat gap is too wide, it can say who says so.

parameters:
  - id: mattress
    type: catalog_ref
    catalog: standards.mattress
    value: us-queen

  - id: max_slat_gap
    type: length
    derived: standards.bed.slat_gap_max

requirements:
  must_satisfy:
    - standards.bed.slat_gap_max
    - standards.bed.centre_rail_required

Listing an id under must_satisfy turns its check from advisory into a requirement of this design.

Four kinds

Kind	Shape	Read as
dimension_set	Named sizes	mattress.width via a catalog_ref parameter
limit	One bound, max or min	standards.bed.slat_gap_max
range	min, max, typical	standards.table.dining_height.typical
rule	A requirement in prose, with a condition	Checked, not referenced

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Beds

standards.mattress — mattress sizes

dimension_set. Source: ISPA standard sizes for the US series; EN 1334 and common European trade sizes for the eu- and uk- series.

Value	Width	Length
us-twin	991	1880
us-twin-xl	991	2032
us-full	1372	1880
us-queen	1524	2032
us-king	1930	2032
us-cal-king	1829	2134
uk-single	900	1900
uk-double	1350	1900
uk-king	1500	2000
uk-super-king	1800	2000
eu-single	900	2000
eu-double	1400	2000
eu-queen	1600	2000
eu-king	1800	2000

These are nominal finished sizes. Real mattresses vary by ±10 mm or so between makers, which is exactly why mattress_clearance should be a parameter with a sane default rather than a number baked into a rail length.

standards.bed.slat_gap_max — maximum clear gap between slats

limit: 76 mm max.

Source: consensus of mattress-maker warranty conditions — Tempur, Sealy, IKEA and others all specify 75–80 mm; 76 mm is the most commonly stated figure and the most conservative in wide use.

Foam and hybrid mattresses sag between slats further apart than this, and most warranties are void above it. Sprung mattresses tolerate more, but there is no reason to design to a looser number.

This is what an array count should be derived from, so that changing the mattress size adds slats by itself.

standards.bed.slat_thickness_min — minimum slat thickness in softwood

limit: 18 mm min. Source: common trade practice for slatted bases at 900–1600 mm spans.

standards.bed.centre_rail_required — centre rail above a threshold width

rule. Applies when mattress.width > 1370.

A bed wider than 1370 mm needs a centre support rail with at least one leg to the floor, so the slats do not span the full width unsupported.

Source: mattress warranty conditions for queen and larger sizes; universally required by US makers above 1370 mm width.

This is DOM-002, and it is one of the four things the validator found wrong with the golden queen bed the first time it ran.

standards.bed.deck_height — comfortable mattress-top height

range: 450 – 650 mm, typical 560.

Source: anthropometric guidance for sit-to-stand transfer; matches the range used in accessible-design guidance for bed height.

This is the top of the mattress, not the deck. Subtract the mattress thickness to get the slat height the design actually controls — a 300 mm deck under a 260 mm mattress gives 560.

standards.bed.mattress_clearance — clearance per side

range: 3 – 15 mm, typical 6. Source: trade practice; accounts for maker-to-maker size variation.

Too tight and the mattress will not drop in; too loose and it slides and opens a gap at the head.

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Tables and desks

Id	Kind	Figures	Source
standards.table.dining_height	range	710 – 760, typical 750	BS EN 1730, BIFMA G1, trade practice
standards.table.desk_height	range	720 – 750, typical 730	BS EN 527-1, fixed-height category
standards.table.counter_height	range	890 – 950, typical 910	Trade practice — European carcass plus worktop
standards.table.place_setting_width	range	550 – 700, typical 600	Trade practice for dining layout

standards.table.knee_clearance

limit: 685 mm min clear height under an apron.

Source: ADA Standards §306.3 and BS 8300-2, which both require at least 685 mm clear for a seated user.

This is the one ergonomic figure that is a hard accessibility requirement rather than a comfort range, which is why it is a limit and not a range. A 750 mm dining table with a 90 mm apron leaves 660 and fails it.

standards.table.legroom_depth

limit: 480 mm min clear depth under a table. Source: ADA Standards §306.3.

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Seating

Id	Kind	Figures	Source
standards.seat.height	range	400 – 460, typical 450	BS EN 1729-1 size mark 6
standards.seat.depth	range	380 – 450, typical 420	Buttock-to-popliteal length, 5th percentile

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Shelving and casework

standards.shelf.clear_height

range: 220 – 400 mm, typical 300. Source: trade practice — paperbacks to large-format art books.

standards.shelf.deflection_limit

limit: span/200 max, expressed as a span divisor.

Source: woodworking convention — sag becomes visible at roughly span/200 and is widely treated as unacceptable beyond it. Structural practice for floors uses span/360, which is stricter than a shelf needs.

A 900 mm shelf may sag 4.5 mm. Use deflection_limit: span/360 in requirements if the shelf sits next to a fixed reference line where sag shows up.

standards.case.toe_kick

range: 75 – 100 mm, typical 90. Source: trade practice for standing-height casework.

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Errors and warnings

The ergonomic ranges drive DOM-003, and they are warnings. A 780 mm table is unusual, not wrong, and the report’s job is to say “this is outside the normal range, and here is the range” rather than refuse to compile it.

standards.table.knee_clearance is the exception, as noted above — an accessibility requirement, checked as a limit.

Anything you list under must_satisfy is checked as a requirement of the design regardless of its default severity.