Seating specs

[The Medway Handyman]

I've been asked to build some bench seating. I'm sure there are standard dimensions for seat heights, widths, depths etc. Anyone know of a source?

Measured my 3 piece but I'd like to make sure.

[RubberBiker]

Can't quote you an open source reference, but I have a copy of "Metric Handbook. Planning and Design Data" Adler - Architectural Press.

Contains vast amounts of that sort of data. If you can be specific about what you want, I'll look it up.

Have also been resizing some church pews this week, so can take some measurements off those if you like.

[Pete Verdon]

Except that every church pew I've ever sat in (admittedly not all that many) has been ergonomically terrible :-)

Pete

[Dave Plowman (News)]

That's to keep you awake. ;-)

[Owain]

Depends if this is for sitting up (at a table) or sitting back (relaxing).

Seat height should not exceed the popliteal height of the user (ie the height of the underside of the knees). A chair which is too high will be tolerated better if the front edge is rounded. A chair which is too high is worse than one which is too low, so the short user takes precedence for a non-adjustable chair. Popliteal height of a 5th percentile adult woman (wearing typical outdoor shoes) is 400mm. Thus the height of a non-adjustable chair should not exceed 400mm or 425mm at the most.

Depth of the seat measured from the front edge of the backrest should not exceed the buttock-popliteal length of a small user (5th percentile woman =3D 435mm). A seat which is too deep deprives the user of the full depth of the backrest., Serious problems arise with easy chairs. People sometimes complain that tseat surfaces are too short, this is usually because the seat is too high or the backrest is too low.

Upholstery. The pressure under the ischial tuberosities of a large bony man sitting on a hard seat may exceed 60psi. Padding the seat surface distributes the pressure over a wider area leading to an increase in comfort and the length of time for which the seat is tolerable. Contouring the seat may have a similar effect - cf traditional Windsor chairs. Exccessively soft upholstery may reduce comfort because the pressure may be spread to sensitive areas such as the underside of the thighs or the outer edges of the buttocks beneath the greater trochanters. As a rough guide the upholstery of a chair shoudl be compressed by 1-2" when you press down hard on it with your hands, but should not 'bottom out'.

Seat angles. For most seats for drivers in vehicles and VDU operators a backrest with an angle of 100-110deg with the horizontal is about right. For easy chairs a steeper rake may be better.

As your back engages with the backrest you slide forward, especially in easy chairs. This is reduced if the seat has high-friction upholstery and a slight backweard tilt eg about 5deg.

For rest chairs a backrest extending to shoulder height (95th percentile man =3D645mm) is desiuirable. A backrest whcih is rated to more than about 100deg should extend at least to mid-thoracic level (say about 500mm above the seat surface). Conversely abackrest extending to mid-thoracic level or higher which is close to the vertical tends to tilt the upper part of the trunk slightly forward (some dining chairs)

In general a backrest should be contoured to the shape of the back. A pad in the mid-lumbar region to support the lordosis reduces intra- discal pressure at any backrest angle. The mid-point of of the curvature of the lumbar pad about 230mm above the seat surface will suit most users of a non-adjustable chair. Curvature of the lumbar pad should not be excessive, a pad which stands out about 40mm from the plane of the backrest gives a lumbar lordosis similar to standing.

Rest chairs. A rest chair should support your back, to shoulder level or more, in a reclined position. Many armchairs are too deep and too soft and are lower than they need to be.

Summarised from: Ergonomics, Work and Health. Steven Pheasant. Macmillan, 1991. 0-333-48998-5

Your 3 piece is probably not at all anthropometrically correct.

[Owain]

And because they were probably designed for people about 100 years ago.

Owain

[Dave Plowman (News)]

My brother is an elder of the local kirk in Scotland and they fairly recently decided to rip out all the pews and replace with movable seating. Quite a large kirk that would seat some 500, and built in the mid 1800s. And the majority of all that lovely pine had to be scrapped. A few were sold to members of the congregation - but the rest were charged for disposal.

[Stuart Noble]

Maybe they didn't put enough feelers out. Easy enough to dismantle, and the seats alone (usually 12" x 1") used to fetch good money from restorers and the like.

[Dave Plowman (News)]

Being good Aberdonians I'm sure they did. ;-)

It's what I thought. But perhaps only in some parts of the country.

[Jules]

I know church seats are uncomfortable - but 12" x 1"? Ouch! :-)

[Owain]

As the choirboys all said...

Owain

[PeterC]

It's the priests' equivalent of the bishopric.

[Stuart Noble]

At least choir stalls normally have higher backs. A lot of them ended up as settles in pubs and wine bars