Guides
Sliding Window Profiles: How the Sections Work
A sliding window section drawing fixes four decisions: how many tracks the frame carries, how deep the sash sits, how thick its walls are, and where the water leaves. Get those lines right and the rest of the specification follows. This guide works through track layouts, sash depth, roller choice, drainage, sealing and glass fit, using the Adam Alux 95 series as the worked example, and closes with a method for reading any sliding section you are handed.
What a sliding section drawing has to answer
Before reading a single dimension, decide what the drawing has to prove. A sliding window has four separate load paths: the head carries the sash weight through the rollers, the jambs guide the sash and take wind load, the interlock closes the meeting stiles, and the sill drains whatever water crosses the track. A section that shows a 1.4 mm sash wall over a 1.0 mm track bed has mixed up its priorities. Print the drawing at full size across the sill, measure with a scale rule instead of trusting a callout, and check that sash depth, track spacing and glazing bead all still clear one another in the closed position. The single most useful dimension is the distance between the outer face of the closed sash and the inner face of the frame, because that number sets the wall reveal and the fixing detail.
Two tracks or three: how the layout changes the window
A two-track frame slides two sashes past each other on separate rails, one inboard and one outboard. Three tracks add a third rail, which lets two sashes stack to one side while a third stays closed, so a wider opening clears without a wider stack. The extra track costs depth: the frame grows in the direction of the wall, the middle rail needs its own drainage path, and each additional sash line creates another meeting point that has to seal. The Adam Alux 95 series is built for both layouts, so a spec writer can keep one frame profile and change the track count with the opening width.
Sash depth and wall thickness do different jobs
Depth keeps the sash from twisting across a wide light, and it gives the interlock enough mating face to stay closed under wind pressure. Wall thickness decides how much load a chambered section takes before it deforms, and where the fixings can bite. The Adam Alux 95 series is drawn at 95 mm profile depth with a 1.4 mm wall in 6063-T5 aluminium, and its sash is a closed-chamber section that adds stiffness across wide lights. Both figures are read straight from the section: depth is measured across the frame as drawn, while wall thickness is measured on an individual chamber wall, never across a chamber.
Roller types and what they do to the slide
Sliding windows fail at the rollers more often than anywhere else, because the roller is the only part carrying the full weight of the sash. A ball-bearing roller spreads that weight over a hardened track and holds its line through years of cycles. A nylon wheel is cheaper and quieter on a light sash, and it flattens under heavy glass until the sash starts to drag. Choice follows sash weight rather than list price, and wide sashes carrying insulating glass need ball bearings. The Adam Alux 95 series runs ball-bearing rollers as standard, which is the sensible default once a sash carries insulating glass across a typical residential light.
Drainage and sealing on the track
A sliding window cannot seal the way a casement does, because the sash travels instead of compressing onto the frame. Water management therefore happens in the sill. Look for an open drainage path: slotted track beds, a sill that falls to the outside, and weeps that stay clear instead of trapping debris. Seal the remainder with compression gaskets at the interlock and around the frame perimeter. EPDM foam gaskets hold their compression as they age, and the open, self-cleaning drainage path of the Adam Alux 95 series keeps the track clear of the silt that eventually blocks a narrow weep. Put track cleaning into the handover routine, because a hidden weep behind a closed sash will not clear itself.
Fitting the glass build-up to the section
The glazing line in a sliding section sets the maximum cavity the frame can hold, so the glass package has to be chosen before the sash is drawn. Insulating units of different thickness need different beads and different setting blocks even when the sight-line stays the same. Standard glazing on the Adam Alux 95 series is 5-20A-5 insulating glass, with single and triple build-ups available on request. Check three things on the section: that the cavity drawn equals the cavity ordered, that the setting blocks sit under the glass rather than on the drainage path, and that the glazing bead still clears the track when the sash slides past the fixed light.
How to read a sliding window section drawing
Work from the sill outward in one pass. Confirm the track count and that the sashes are offset correctly. Measure the frame depth, then the individual chamber wall on the sash. Find the roller position and check that the load lands on the track bed rather than on a stop. Trace the drainage path to the outside and confirm there is a fall. Locate the interlock gasket and the perimeter gaskets. Mark the glazing line and compare its cavity with the glass build-up on order. Any line you cannot trace is a question for the supplier, and the supplier who answers it with a dimensioned pack is the one worth keeping on the shortlist. Ask for that pack in PDF, with CAD available on request.
FAQ
Frequently asked
What is the first dimension to check on a sliding window section?
Frame depth, then the individual chamber wall on the sash. Depth governs how much a sash can twist across a wide light and how much interlock face it gets. Wall thickness governs how much load the section carries and where a fixing can bite. The Adam Alux 95 series is drawn at 95 mm depth with a 1.4 mm wall, so both figures are read straight off the section.
Is a three-track slider better than a two-track one?
Only when the opening needs it. Two tracks slide two sashes past each other on separate rails. Three tracks add a rail so a wider opening clears without a wider stack, at the cost of frame depth, an extra drainage path and one more meeting point to seal. The 95 series supports both layouts on the same frame profile, which makes track count a project decision.
Do ball-bearing rollers matter on a residential slider?
They matter as soon as a sash carries insulating glass. The roller takes the full sash weight, and a nylon wheel flattens under a heavy unit and starts to drag. Ball bearings spread the load over a hardened track. The Adam Alux 95 series runs ball-bearing rollers as standard, which suits residential lights carrying the standard 5-20A-5 insulating build-up.
What glass can a sliding window frame take?
Whatever its glazing line is drawn for. The cavity shown in the section sets the maximum unit thickness, so the glass build-up is chosen before the sash is drawn. Standard glazing on the 95 series is 5-20A-5 insulating glass, with single and triple build-ups available on request in the same sight-line. Confirm the cavity on the drawing matches the cavity on the order.
Where does the water go on a sliding window?
Into the sill. A sliding sash cannot compress onto the frame the way a casement does, so the sill does the work: slotted track beds, a fall to the outside and weeps that stay clear. The Adam Alux 95 series uses EPDM foam gaskets at the interlock and perimeter with an open, self-cleaning drainage path. Keep that path clear, because a blocked weep shows up as a wet floor line.
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