Sash weights

[Vala]

I'm really intrigued that every window I've worked on so far in my house has used 7 Lb sash weights. A 24"x70", and a 28"x70", a 28"x56" - and even in another house that had almost 8 ft tall windows also had 7 Lb weights. I know the sash weight thing isn't an exact science but even I wasn't expecting to almost always encounter 7 Lb weights. In fact on occasion that I get some salvaged sash weights, they are nearly always 7 Lb weights.

[Manalto]

Years ago I rigged a counterweight to close a garden gate, an inelegant set-up using a partially-filled plastic soda bottle in anticipation of a classier solution that never came to pass. I was surprised at how little weight was necessary to close (rather than slam) the gate; I wonder if the principle is the same. It's still unusual that 7 lbs. would be the sash weight of choice for such a wide range of window sizes.

[heartwood]

it's just a coincidence...I rarely see 7 pound weights...our last few projects had 4, 5, 8, 18 and 29 pound weights...it's not the size of the sash it's the weight....if the weights hold the sash at the desired height, then they are the correct weight....
....jade

[Manalto]

I didn't think it was the size of the window that mattered. I was assuming, perhaps incorrectly, that an eight-foot window would weigh more than an 18" one.

[Mick_VT]

I didn't think it was the size of the window that mattered. I was assuming, perhaps incorrectly, that an eight-foot window would weigh more than an 18" one.

To an extent, but glass thickness and type, and the construction of the sash itself (number of panes and type of wood, thickess and side of the rails) , leaded or non-leaded, would also affect the weight

[Manalto]

That's true.

[Sashguy]

Not uncommon over a 100 year span to find incorrect weighting. To some homeowners and handymen, a weight is a weight. I did a home last week where I was finding windows with a 5# on one side and an 8# on the other. Of course, the sashes all kicked side-wards and jammed, but they would eventually wiggle up. Once corrected, the homeowner was like "It's magic".

[vvzz]

When I was working on the facade bay last year, I was able to take out a whole bunch of weights from the pockets since I replaced some of the siding and the it was easily accessible. There were like two extra weights per sash - they just kept adding them once the ropes broke. Needless to say, they all were different weights.

[mjt]

Not uncommon over a 100 year span to find incorrect weighting. To some homeowners and handymen, a weight is a weight. I did a home last week where I was finding windows with a 5# on one side and an 8# on the other. Of course, the sashes all kicked side-wards and jammed, but they would eventually wiggle up. Once corrected, the homeowner was like "It's magic".

I know you know this, but it's not magic; it's simple physics.

The lack of understanding about the simplest science-related things saddens me.

[Mastercarpentry]

Ideally, sash weights will perfectly balance a window and be equal on both sides but it's never been a perfect world and there's never been a perfect carpenter building them. If you needed 11 lbs balance you used a 5# and a 6# because 5 1/2# weights didn't exist Unlike today's construction, waste was a cardinal sin in the old days so if you had something on hand then you used it if it would work. I suspect weights were reused and whatever was on hand was put to work in the building of all but the finest old houses, which would explain the oddities sometimes found with sash weights. Ball-bearing smoothness and perfect balancing didn't exist back then so that too is another reason for the oddities. What I find oddest of all is that the 'modern' answer of spring balances will wear out and need replacement, but sash weighted windows done well need only a bit of rope and a drop of oil once in awhile to keep working as designed forever.

If the sash works smoothly and stays where you put it then there can't be too much wrong with it. If not, then you fix it. Nothing new there!

Phil