Measuring a Sealed Glass Unit



I have had the inner glass of a large sliding door shatter (cracked ice) and five minutes later drop out in a million pieces. The outer glass is intact.
I want to order a new SGU, but I am not sure how to measure the thickness of the unit. I don't want to remove the unit from the frame until I am ready to install the new unit.
The door is between 15-20 years old. The glass size measured from opposite outer beading edges is 1115mm wide and 1790mm high. The glass is 4mm thick, the gap, I can only measure roughly and make it about 15mm. Does this gap sound about right?
Anybody got any suggestions about changing the glass thickness and to what. How much should I deduct from the height and width of my measurement? Any help or suggestions would be gratefully received.
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Whats the patio made of, upvc of ali? Need this to advise how to measure.

Thickness, you already know the shattered pane is 4mm, its safe to assume the other pane is too then, the spacer bar you suggest is 15mm or close, well your about right, spacer bars start at 4mm and go upto 20mm in 2mm increments, through my experience you will have a 16mm spacer, 14mm was very very very rare.

The thickness make up of your unit will be 4/16/4, i.e a 24mm unit, this is how glass shops like the measurement to be expressed, all you need now is the width and height and whether you require a low E glass, you'll of course need toughened glass as well but i guess you already know that, but make sure the glass shop do too, otherwise you'll end up with a float unit :cry:
The door has a upvc frame. Thanks for the quick and informative reply. My knowledge of SGU's tripled with just a few sentences from you. I now await your reply on the correct way to measure the glass.
Ok with a upvc system what you need to do is look at the glazing beads that hold the glass in, you should see a joint between the beads and frame, measure from this joint over to the other bead joint and deduct 10mm, do this for the width and height, knocking 10mm off will give you a 5mm gap all the way round the unit once in the frame. If your planning on changing the glass yourself then you need to remove the beads anyway (obviously), you might want to measure the glass this way if your unsure of measuring with the beads still in situ.
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Thanks Crank39. You have answered my questions completely. I am now confident to do the measuring and place the order for the unit.
Now you have got over the hurdle of measuring and ordering a new sealed unit do you know how to fit it?
Be carefull not to damage the upvc glazing bead. The unit can either be externally or internally beaded. Usually with upvc beads on the inside you insert the external rubber gasget 1st, then the glass goes in from the inside which sits on the internal lip of the extrusion. The glass WILL need packing. You should be able to use the existing packers. This all done you fit the internal upvc beads, they can be tricky to line up but they usually just clipped in (rubber mallet may be required, or block of timber)

However sometimes the upvc beads are external, and the glass is fitted from the external. In which case the glass goes in first, (from the outside) then the external beads are clipped in. Now the important bit. You lubricate (washing up liquid is good) the internal rubber gasket (usually its wedge shaped, we call it a wedge gasket) also lubricate around the glass ede, and push glass as firmly as possible outward, this compresses it back onto the external upvc bead (much easier done face down on a bench when the door was made but not so easy on site). Then push the rubber wedge in gap all round the inside. Basically this stops anyone removing the outer beads for security reasons.
Do in the wrong order or without lube you will damage either rubber wedge or upvc beads.
All the best Steve.
Hope its not in with glazing tape :cry: - went to a callout Fri on an 1800 french pair, both sashes dropped (like draggin..)over the threshold, but externally beaded with glazing tape - heel and toe not an option :rolleyes: managed to adjust hinges to minimize drag but nightmare glazing tape strikes again
Can't understand why you should struggle? Stanley knife the tape, remove glass, scrape remaining tape off doors and glass, renew tape to doors, place a 5mm glass packer on top of shootbolt keeps and shut door over them, then toe and heel door in the position it sits, open door, remove glass packer, door should now remain in a toe and heeled position with a 5mm gap above the keeps :D

Or another way is to spray the glazing tape with glass cleaner so the glass won't stick, toe and heel as normal, once glass cleaner evapourates the glass will stick to glue :LOL:
Top idea with the solvent cleaner Crank - never thought of that one :oops: didnt have enough on the roll to reglaze both doors, supplier shuts 3.00 on Friday (alright for some)Cheers

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