Hinge Position and Number?

[BruisedThumb]

Hi,

I've just got home from a few days in hospital. Looking round the place I noticed that the doors between the main ward and various side wards/offices/sluice rooms etc. all had three hinges. The doors are good massive hardwood doors and the hinges each have two ball-races.

The bit that intrigued me was that each door has three hinges, one at the bottom and two, quite close together, at the top of the door.

I've heard that the (two) hinges on a domestic door should be positioned 'six down and nine up' but what's the rationale for this two at the top and one at the bottom layout?

If it's to withstand the impact from beds or trolleys, surely the two hinges should be at the bottom?

 

[masona]

Hope you are well,

Because they are fire door and very very heavy so need extra support at the top. We used to put hinges in the middle and found it stronger by putting it nearer to the top hinge.

 

[chappers]

As Masona says with heavy fire doors the bottom hinges will be compresed into the linning whereas the weight of the door will try to pull the top hinges away from the linning hence biasing the third hinge towards the top

 

[BruisedThumb]

Thanks for that, guys.

I'd been trying to understand it solely on the basis of the vertical forces (as far as the weight of the door is concerned).

I hadn't considered the horizontal forces. It all makes sense now.

Thanks again.

'Sa wunnerful thing, this Interweb thingie, innit!