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:
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.
Best Answer
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
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.