There's nothing that limits it to electrical afaics, so its wide open. And within electrical it might refer to a junction box, a small CU, and assorted items that arent part of house wiring.
NT
How does the disambiguation feature of a wiki work? I've not played with that at all.
Then the whole idea is pointless.
Are these more obscure terms?
Plenty of electrical bits and pieces consist of a plate of some sort which fits a box. But with all the JBs and CUs I've seen the 'guts' are in the box rather than on the plate.
Disambig can be either its own separate page or a section in a page. In this case the latter seems more suitable, since its unlikely we'd have a page for the other pattresses any time this year
When I get time I'll do all the work and re-draft the article
NT
That corresponds to my usage and the usage of people that I deal with here in Cheshire. Surface fittings have pattresses. Flush fittings have back boxes. It's a simple and useful distinction.
Hopefully the final draft now, with lots of input added...
'''Pattress''' usually means the box that sits behind electrical sockets and switches, though it has other meanings too. Modern electrical pattress boxes come in metal and plastic, and in surface mount and flush versions.
=3D=3DUses of the word 'pattress'=3D=3D 'Pattress' has more than one meaning in DIY. Its also a word whose meaning has changed relatively quickly over time, resulting in significant disagreement over which meanings are correct.
=3D=3D=3DHistory=3D=3D=3D [[image:Socket_(__)_785-4.jpg|thumb|old wood pattress plate]]
Pattress is derived from the latin 'pateras' meaning a shallow bowl or plate.
In the 1800s 'pattress' was used to mean the flat wooden plates that gas lighting equipment was mounted on.
In the 1930s electrical accessories were mounted on wooden plates, and these were mainly referred to as 'pateras.' The anglicised version 'pattress' gradually took over from pateras.
When wiring regs required electrical accessories to be housed in fireproof containers, a box was used between the wooden pateras and socket, instead of mounting it directly to the pateras. This was known as a pattress box. Over time this became known as a pattress.
Today many trade and DIY people refer to any electrical backbox as a pattress. There are also many that consider only surface mount boxes to be pattresses, and many that don't call any type of backbox a pattress. Unfortunately this is equally true of the other names for these things, so we just have to be aware of the differing usage of the term.
The electrical boxes used behind sockets and switches are variously known as pattresses, wiring accessory boxes, boxes, and backboxes, with none of these terms being universal.
=3D=3D=3DNon-electrical pattresses=3D=3D=3D The word 'pattress' also describes flattish iron plates used for load spreading, as used to tie houses with structural defects together.
=3D=3DPattress types=3D=3D
=3D=3D=3DMetal flush mount pattress=3D=3D=3D [[image:Pattress metal 406-3|thumb]] Metal recessed pattresses are used to mount sockets & switches flush to a solid wall. A recess is chiselled out for the pattress to sit in. Knockouts are provided for [[cables|cable]] entry. These are the most common domestic pattresses.
=3D=3D=3DPlastic surface mount pattress=3D=3D=3D [[image:Pattress dbl 759-4.jpg|thumb]] Plastic surface mount pattresses are used for electrical accessories that sit on the surface of walls. The pattress is [[screws|screwed]] in place, and knockouts are provided for [[cables|cable]] entry, either via the sides or the rear.
These are available in different depths. The shallowest ones are suitable for light switches where no screw block connections need to be made behind the switch. Deeper ones are usually used for sockets, but fitting sockets into shallow patresses is often possible, if tight, and light switches with a few screw block connections behind them will need the deep ones too.
Plastic surface mounting patresses are the second most common domestic type.
=3D=3D=3DStud wall pattress=3D=3D=3D [[image:Pattress PB 757-5.jpg|thumb]] Plasterboard boxes are used to flush mount switches etc to [[Sheet Materials|plasterboard]]. The picture shows the position of the grips before and after fitting.
=3D=3D=3DArchitrave pattress=3D=3D=3D Architrave pattresses are used with little architrave switches.
=3D=3D=3DMetal surface pattress=3D=3D=3D [[image:Metal skt & pattress 754-7.jpg|thumb]] Metal surface pattresses aren't very common in homes. They are used with metal accessories, and are ideal for workshops (and other environments) requiring particularly tough accessories.
=3D=3D=3DTwin single pattress=3D=3D=3D [[image:Twin pattress 849-4.jpg|thumb]] Twin pattresses are designed to take two single accessories. These are used when 2 different accessories in one position are wanted. These are not the same size as a double pattress.
=3D=3D=3DNon-standard pattress=3D=3D=3D [[image:Pattress ashley 758-5.jpg|thumb]] Non standard pattresses are sometimes seen. These generally don't fit standard sockets. They're designed to achieve some advantage, such as styling or compact size.
=3D=3D=3D3 & 4 gang pattress=3D=3D=3D
3 way socket convertors use a pattress designed to [[screws|screw]] onto the top of an existing single flush mount pattress. These turn a 1 way flush socket into a 3 way surface mount socket. Sometimes the [[cables]] aren't long enough and need extending.4 way socket convertors...
=3D=3D=3DGrid switches=3D=3D=3D (pic wanted) Grid switch pattresses are another type not often seen in homes. These accept a number of accessories, which can be mixed at will in the one box. Available accessories include various switches, dimmers, key switches, indicators, etc. The accessories don't have any face plate, a single full size faceplate is fitted last. MK is known for its grid switch range.
=3D=3D=3DRound conduit boxes=3D=3D=3D Round boxes forming part of a conduit system are sometimes seen in houses, though not often.
=3D=3DJunction boxes=3D=3D [[image: |thumb]] [[Cables]] are often joined in pattresses, but their purpose is for mounting switches and sockets. When a container is wanted only for joining cables, a junction box is smaller & cheaper.
=3D=3DDepth=3D=3D Plastic surface pattresses are widely available in different depths, ranging from 16mm (mainly for switches) to 47mm (mainly for sockets).
Other types of pattress are also found in different depths, but less often.
=3D=3DThermoplastic and Thermoset=3D=3D [[image: |thumb]] Plastic pattresses intended for mains use are made from thermoset plastics, mainly white bakelite. These don't soften when hot, and act as a fire resistant container.
Similarly sized pattresses intended for phone networks are generally made from thermoplastics. These come in more than one size, the larger of which fits mains sockets. These can be bent slightly by hand, so are easily recognised. They offer no heat or fire protection and don't meet modern safety requirements for mains use.
=3D=3DStyle & fit=3D=3D [[image:Pattress corner detail Egatube & Tenby 850-4.jpg|thumb|Egatube vs Tenby]] Different brands of pattress have different corner detailing, intended to match their own brand of accessories. Standard pattresses, switches and sockets of different brands can be freely mixed, but the difference in corner detailing can make a minority of combinations look wrong. If mixing brands its best to check they look right together before buying.
Non-standard pattresses can't be expected to fit standard sockets.
=3D=3D=3DMetal accessories=3D=3D=3D [[image:Socket metal misfit 807-6.jpg|thumb|Oops!]] Many metal accessories for surface mounting are a different size to plastic pattresses. The screw spacing is the same, but the outer size isn't. These are an eyesore if one type is fitted to the other.
This problem doesn't occur with the various retrofit metal accessories on the market designed to fit standard plastic pattresses (and recessed metal ones). It only applies to the traditional functional metal sockets & backboxes.
=3D=3DBreakage=3D=3D [[Screws]] holding plastic pattresses in place should be done up until the screwhead touches the pattress surface, and no more. Any further tightening is likely to break the brittle plastic.
Budget brand plastic pattresses can suffer a significant breakage rate during installation, particularly if a fair amount of hole needs to be made for [[cables|cable]] entry, or if the underlying wall is not competely flat, or the installer doesn't appreciate their frailty.
=3D=3DEarth connection=3D=3D Metal pattresses have an earth terminal for connecting to the circuit earth. A sleeved wire should be run from the socket earth terminal to the backbox.
=3D=3D=3D2 core wiring=3D=3D=3D A small minority of houses still have old 2 core [[lighting]] circuits. Metal pattresses or accessories should not be fitted to such circuits due to the absence of anything more than functional insulation as protection against shock.
Sometimes people fit them and borrow an earth from a nearby socket circuit. This works but its not considered best practice, as there's always the possibility of the socket circuit being decommissioned later, leaving the [[lighting]] accessories unearthed. Hence its not wiring regulations compliant.
Plastic pattresses and accessories are the only type recommended for these circuits. However that doesn't imply that fitting them is always safe; some [[Historic Mains Cables|historic rubber wiring]] is so badly perished that moving the wires during fitting is sometimes a sizeable risk. If perishing is limited to just the wire ends, sleeving may be fitted to replace the function of the damaged insulation.
=3D=3DExtension leads=3D=3D Surface pattress boxes are not designed for use on extension leads. They have no cordgrip, and are brittle, which is not ideal for portable use. Despite this they see fairly widespread use in extension leads, so we will describe how to make these not-recommended leads as safe as possible.
The main problem is the lack of cordgrip. There are 4 ways to implement a cordgrip. # Knockout 3 of the knockouts in a row on one side/top/bottom of the pattress, and thread the lead through all 3 in a zigzag pattern. This makes a fully effective cordgrip. # The pattess box can be mounted on a piece of wood and a cordgrip from a mains plug used to secure the lead inside the box. The 2 screws go into the backing wood. # Knotting the wire is sometimes used, but this is only partially effective. # A few surface pattress boxes do have cordgrips (eg Marbo).
Breakability can be reduced to some extent by mounting the pattress box on a piece of chipboard that's larger all round than the box. Chipboard and MDF are best as they're soft enough to reduce peak impact forces.
=3D=3DSee Also=3D=3D
[[Category:Electrical]]
NT
what are those white plastic spacers that can (Could) be bought to effectively increase the depth of a box by bringing the wiring accessory forward about 6mm?
IIRC, called mounting frames.
Added, thanks. Just got the images to sort out now.
NT
Added, thanks. Just got the images to sort out now.
NT
Thanks - I was trying to refer to one recently but didn't know the name and couldn't find them.
I've never used them - didnt even know they existed. I expect someone else here has more experience of them
NT
Yes - although you'll have to modify it somewhat. They have normal 2.5mm fixing threads - so if you wish to put it between accessory and backing box you'll need to drill them out. You may also need to remove the spare 'lugs' as these can interfere with some fittings.
It will look a bodge, though.
The message from "Dave Plowman (News)" contains these words:
For a start, the machine screws are M3.5 -- that is the normal variety for electrical boxes
You're not usually expected to drill them out but rather to use one set for mounting the spacer and the other set for mounting the accessory. Of course that sometimes causes problems of orentation and fitting of some accessories.
Indeed.
Most will tend to get used with plaster depth boxes which have only two fixing lugs.
And you're not 'expected' to use them for this purpose - they're for mounting a standard accessory to trunking etc. Use as a spacing frame is a secondary one.
Some boxes also have only one adjustable lug - which most would fit so it can be used for horizontal fixing. See also my point about the large plastic lugs at the top fouling some dimmers, etc.
ah, well if you use the things designed for the purpose of extending a backbox rather than those designed for conduit, it all works much better
- the same screws just fit through the unthreaded lugs on the extender and go into the original back box:
The message from "Dave Plowman (News)" contains these words:
And many boxes have -- or at least in the past had -- no adjustable lugs :-(
Been there, done that, got the t-shirt. Often :-(
Whilst they may still be current catalogue items, I think we're dealing with something which is largely a relic of the past. I dare say I could probably find one or two in a box of old bits somewhere around my storeroom, but then I could also find a few packets of mounting flanges. Remember them? Used to use them on 4 lug single-gang metal back boxes. Fix flange to box using two of the lugs, then fix box to skirting by woodscrews through the face of the flange. A whole lot simpler ( and easier to align) than screwing through the side of the box into the thickness of the skirting. But then flange boxes became readily available and the problem was solved in a different and simpler way.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.