Friction Stay Hinges vs Butt Hinges for Casement Windows: Selection & Load Guide

Two different philosophies of casement window operation

When designing an outward-opening aluminium casement window, fabricators face a fundamental architectural choice: hang the sash on external butt hinges, or fit concealed stainless steel friction stay hinges inside the perimeter groove.

Both carry the weight of the sash. But how the window behaves once you open it into the breeze is completely different.

Butt hinges leave the sash swinging freely like an internal door, demanding a secondary sill hook or casement peg stay to keep it open. Friction stays tuck completely into the perimeter rebate, holding the window firmly at whatever opening angle you leave it, with no visible hardware on the outside.

Here is how to calculate loads, select stay lengths, and choose the right mechanism for your architectural window schedule.

How a friction stay hinge works

A friction stay consists of four or five linked stainless steel arms connecting the outer frame track to the sash bar.

As the window pushes open, the arms scissors outward, moving the pivot point along the frame channel. Inside the track channel sits an adjustable brass or nylon friction slider. By turning the adjusting screw on the slider shoe, the fabricator tunes the resistance.

This friction holds the sash stationary against moderate wind forces without needing peg stays, casement hooks, or sill brackets. Furthermore, as the window swings open, the hinge-side stile pulls away from the frame by 80 to 100 mm, leaving a gap wide enough for an occupant to clean the exterior glass face from safely inside the room.

Where traditional butt hinges still make sense

Standard aluminium or stainless steel butt hinges pivot around a single fixed axis.

Their strengths are simplicity, extreme weight capacity, and wide opening angles. A heavy pair of extruded aluminium butt hinges (or 2D/3D adjustable hinges) can easily support an oversized sash weighing 60 to 80 kg, swinging fully 90° or 180° flat against the wall.

However, butt hinges do not hold an open position on their own. If an occupant pushes the window open on the fourth floor of an apartment during a Chhattisgarh pre-monsoon thunderstorm, a sudden cross-draft will slam the shutter shut or violently whip it backward, bending the frame or shattering the glass unless a manual stay hook is securely latched.

Top-hung vs side-hung friction stay geometry

Friction stays come in two distinct geometric configurations that must never be mixed up:

Top-hung stays (for awning windows): The friction stays are installed on the two vertical side jambs. The sash hinges outward from the top edge, swinging upward like a visor. Because gravity acts downward along the length of both stays simultaneously, top-hung stays carry heavier glass weights (typically 20 kg to 55 kg) and open to approximately 30° to 50°.

Side-hung stays (for casement windows): One friction stay is fitted along the top horizontal frame head, and the other along the bottom sill. The sash swings outward sideways like a door. Because the entire dead load of the glass hangs as a cantilever off the bottom track shoe, side-hung stays must be sized strictly to the sash width and carry lighter maximum loads (typically 18 kg to 35 kg).

Calculating sash load and selecting stay length

Never guess the length of a friction stay. A stay that is too short will twist under wind load, while an oversized stay will restrict the opening angle.

Step 1: Calculate the glass weight Glass has a universal density of 2.5 kg per square metre per millimetre of thickness. - Width (m) x Height (m) x Glass Thickness (mm) x 2.5 = Glass Weight in kg. - Example: A 1.2 m high x 0.6 m wide window with 5 mm toughened glass = 1.2 x 0.6 x 5 x 2.5 = 9.0 kg.

Step 2: Add the aluminium profile weight A standard aluminium casement sash frame (including corner cleats, glazing beads, and gasket) adds 3 to 5 kg. Total sash weight = ~13 kg.

Step 3: Select stay length based on sash dimension - For side-hung casement windows: The friction stay length should cover between 60% and 80% of the sash width. For a 600 mm (24-inch) wide sash, install a 16-inch (400 mm) side-hung stay. - For top-hung awning windows: The friction stay length should cover between 75% and 90% of the sash height. For a 900 mm (36-inch) high awning sash, install an 18-inch or 20-inch top-hung stay.

Stack height: 13 mm vs 17 mm clearance

Before ordering friction stays in bulk, measure the depth of the clearance cavity between the outer aluminium frame rebate and the sash extrusion.

13 mm stack height: The standard Indian and Euro-groove architectural standard for aluminium casement profiles (including Domal and standard 40mm casement suites). The folded stay arms collapse into a 13 mm thickness.

17 mm stack height: Designed for deep-rebate commercial aluminium systems, curtain wall vents, and UPVC profiles where the air gap is wider.

Installing a 17 mm stay into a 13 mm profile cavity will bind the sash before it closes, while fitting a 13 mm stay into a 17 mm cavity leaves a 4 mm gap, preventing the perimeter rubber weatherseal from compressing.

Stainless steel 304 vs plated steel in Chhattisgarh climate

Friction stays live in the perimeter rebate—the exact zone where exterior rainwater drains and condensation collects before venting out through weep holes.

Zinc-plated or MS friction stays rust within one or two rainy seasons. Once rust pits the sliding track or binds the brass slider, the homeowner must force the window shut, which shears the pivot rivets.

At Salasar Hardware, we exclusively supply Grade 304 (18/8 austenitic) stainless steel friction stays. SS 304 withstands high humidity, monsoon rain, and industrial airborne pollutants without pitting, ensuring the multi-link arms glide smoothly for tens of thousands of cycles.

Fabricator specification checklist

When placing your order for a casement window project in Raipur or across Chhattisgarh, have four numbers ready: 1. Window type: Side-hung casement (opens sideways) or top-hung awning (pushes out from bottom). 2. Sash width and height in millimetres. 3. Glass thickness (5mm, 6mm, or double glazed unit). 4. Stack height cavity (13mm standard or 17mm deep).

We stock heavy-duty SS 304 friction stays in 8", 10", 12", 14", 16", 20", and 24" lengths, complete with stainless steel mounting screws and adjustable tension shoes, ready for same-day workshop pickup in Raipur or bulk carton dispatch.