For most people, yes, sliding secondary glazing kits will work on your windows.

Sliding kits fit inside the window reveal or onto the face of the existing frame, so they work with timber, uPVC, aluminium and old metal-framed windows, of all styles – whether you have casement, sliding, sash, or any other style of window – you don’t have to have sliding windows to install sliding secondary glazing.

There are some things worth checking before you order, though:

1: Is the window square and level? Trackglaze relies on a straight, level track, so it needs a reasonably square, plumb opening. If your reveal is noticeably out of true – common in older cottages and anything with settled lintels – choose SmartSlider instead. We make SmartSlider to your exact measurements, so it’s far more forgiving of an imperfect opening.

2: How big is the window? Trackglaze is recommended for panels no larger than 1,000mm in either direction using 4mm acrylic or plate polycarbonate, or 1,500mm using glass. Go beyond that and the panels flex and drag.

SmartSlider covers larger openings. The 2-panel unit runs from 600mm to 2,000mm wide and 300mm to 1,800mm high; the 3 and 4-panel units cover wider spans again. Each product page shows the exact minimum and maximum it will accept, and the form won’t let you enter a size we can’t build.

3: Is there room for the frame? SmartSlider has a 44mm frame depth, so you need that much clear space in the reveal, or you’ll need to face-fix it to the window frame instead. Check for anything in the way while you’re there: window handles, trickle vents, deep sills, radiator tops and blind fittings are the usual culprits. Handles that project inwards are the most common reason a reveal fix becomes a face fix.

Measuring takes about two minutes. You only need a steel tape and a pencil.

Measure the width in three places – top, middle and bottom of the reveal.

Measure the height in three places – left, right and centre.

Use the smallest measurement of each. Reveals are rarely perfectly square, and working from the smallest figure means the unit will always go in. Any small gaps get packed out and sealed on installation.

Measure the depth of the reveal from the face of the wall to the nearest obstruction on the existing window.

Work in millimetres. Our kits are ordered mm, and mixing units is the single most common cause of a unit that doesn’t fit.

Don’t deduct anything for tolerance. Send us the reveal sizes exactly as you measured them – we allow for the fitting clearances when we build. For SmartSlider you enter those two figures (width and height) straight into the product page, and we make the unit to suit.

This is hard to say without seeing the window, however if for example, your window is bay-shaped, arched, or has a stone mullion running through it, send us a photo and a sketch and we’ll tell you honestly whether a sliding kit – or any type of secondary glazing – will work for you.

Both our Trackglaze and SmartSlider secondary glazing ranges are designed to be fitted by a competent DIYer in an afternoon. No specialist tools and nothing done to the original window that can’t be undone.

Trackglaze arrives as a kit of parts: three lengths of top sliding track, one length of bottom track, a length of angle that acts as the handle, and a coil of bristle seal. You cut the tracks to length with a fine-tooth saw, screw or bond them to the reveal, fit the bristle seal and drop the glazing in.

Note that glazing isn’t included – order 4mm acrylic or plate polycarbonate from us and use the cut-to-size service so the panels arrive ready to fit. Kits come in 1m and 2m component lengths, in white or brown uPVC.

SmartSlider arrives largely built. The glazed panels come fully assembled, and you fix the four made-to-measure outer frames into the reveal (reveal fixed) or onto the existing window frame (face fixed), then slot the panels into their runners. Silicone around the perimeter finishes the job.

Every product page carries a downloadable step-by-step installation guide (PDF), and the SmartSlider pages include fitting videos.

Yes, of course. The panels slide sideways, so you can slide them open and reach the original window to open it, clean it or use it as a fire escape – regardless of your window type.

While you should check with your local authority before installation, yes, all types of secondary glazing – including sliding secondary glazing – is usually permissible on listed buildings and in conservation areas.