I'm currently trying to design a timber box sash window.

I've had a look at both "traditional" designs from books, and more modern double-glazed window designs, and most have the same general arrangement:

sash window sections

There are two sashes in the frame, the top/outer sash and the bottom/inner sash. The outer frame is built as a box in the factory. On site, the frame is fitted into the brickwork (often behind a reveal to mask the large sections needed to house the balance weights).

Next the outer sash is placed into the frame, the parting bead (which separates the two sashes, acting as a runner, and also holding the outer sash in place against the frame rebate) is hammered into a groove in the frame, then pinned into place with glazing pins or similar.

Then the bottom sash is placed into the frame, and the staff bead on the inside is pinned in over the top to hold this sash in and also act as a runner face.

The sashes then lock together in the closed position by a catch at the meeting rails.

What gets me is that the parting bead is what's keeping the bottom sash from being pulled out to the outside of the frame, but it's also visible/accessible from the outside. What's to stop somebody either chiselling off or levering away the parting bead, then yanking the bottom sash out of the frame towards them?

I've found a product that claims to address this here but the end result is that the parting bead is fixed into place via screws which are still accessible from the outside of the frame. They call it "secure" because the screwdriver bit needed is a "Torx" bit (star key), but in my experience any standard multi-bit set has a number of these in these days, so they're not exactly exotic and this doesn't really seem to solve anything.

How can I change the fixing method of the parting bead or alter the design in such a way that it's secure?

Assume that the frame is fitted with the most secure glazing available - I'm not interested in debates about the glazing as this is largely a solved problem.

migrated from woodworking.stackexchange.com Apr 14 '15 at 15:59

This question came from our site for professional and amateur woodworkers.

  • Agreed, this belongs over in home improvement. If it gets moved I'll respond there. – keshlam Apr 7 '15 at 12:46
  • as ratchet freak notes on chat, this could even fit in security.SE with the "physical" tag. – drs Apr 7 '15 at 17:05
  • My rationale for asking the question here was "who is likely to know about this quite specific question about wooden windows?" and in my head my answer was "woodworkers or joiners!". – WhatEvil Apr 8 '15 at 7:56
  • @WhatEvil I'm still not sure this is a woodworking question since woodworkers don't necessarily know about window construction. However, you do give a basic primer. It would be helpful if you added labels to the various parts of the windows for clarity. – rob Apr 8 '15 at 16:56
  • 4
    What's to stop somebody either chiselling off or levering away the parting bead, then yanking the bottom sash out of the frame towards them? Once you've solved that problem, what's to stop someone from putting a brick through the large piece of glass? I think that's a much higher priority, unless you're using something bullet-proof. Frankly, I think worrying about someone taking the time to pry the parting bead out is giving your average house burglar way too much credit. – FreeMan Apr 9 '15 at 16:18

Being in the security trade, I can tell you that burglars are smart. It doesnt really matter if they know about that particular shortcoming or not. The main element to theft is speed. It will simply take too long to fiddle around with the bead strip in the hope to neatly displace the window. If someone wanted to get into your house a crowbar and a good kick will do the job just as well!

With that said.. its your job to make as many aspects of your home as secure as possible. The sash security parting bead is probably the best thing you can do if you dont like the bolts, try fixing it with one way screws enter image description here

Another option is to drill a metal pin into the bottom portion of the bead, but you may end up doing some damage. Or you could get some brass or stainless screws drill pilot holes into the bottom of the beading, set your screw till the head is almost in, then get a hacksaw and remove the head of the screw, then polish with a file.. that way, if they remove the beading there will still be a pin to make life more difficult.


I know this is an ancient thread. The lower sash still can't be pulled out of the house because the portion of the window frame that holds the upper sash in also prevents removal of the lower sash. In my victorian that frame is substantial, and is not letting any intact sashes out, period.


Any theif will find a way in, if they really want to get inside. Them main thing is to make your property less inviting than next door!

On a sash, the outside of the frame has no beads. The sash box retains the sashes. As long as the sashes are locked together, then they are reasonable secure. Breaking the windows is just as easy an quicker than fiddling about with beads...

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