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Our Spring Sliding Sash Windows retain the appearance of a classic sash while using a modern spring balance system in place of cords and weights. This makes them slimmer, easier to install, and straightforward to operate, while still providing smooth sliding movement.
Each window is manufactured in engineered timber, available in redwood, hardwood, Accoya or oak, and finished with a durable three-coat factory-applied paint or stain. With U-values as low as 1.4 W/m²K and acoustic ratings up to 39 dB, they meet today’s performance expectations without compromising style.
Options include applied glazing bars, varied cill projections, concealed trickle ventilation, and a choice of ironmongery finishes. Tested for weather resistance and designed to last for around 60 years with maintenance, these Spring Sash Windows provide a practical, long-term solution for both traditional and modern properties.
Product Guidance
| Frame | 55 x 160 mm (lining width x frame depth), manufactured using mortise and tenon joints, glued and mechanically fixed. |
| Sash | 39 x 55 mm top rail and stiles, 90 x 55 mm bottom rail, 45 x 55 mm meeting rail. |
| Mullion/transom | 110 mm wide (70 mm for triple sash with fixed outer sash). |
| Sill projection | 35 mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, 110mm. |
| Staff / parting beads | Timber. |
| Wood moisture content | 12-19%. |
| Glazing beads | Internally beaded. |
| Air Permeability | 600 Pa (Class 4) EN 12207: 2017 |
| Water Tightness | 200 Pa (Class 5A) EN 12208:2002 |
| Wind Resistance | 1600 Pa (Class 4C) EN 12210:2016 |
| Whole Window U-Value | Thermal performance is calculated by the standards of EN ISO 10077-1:2006 and achieves a U-value of 1.5-1.4 W/m²K depending on the type of timber, unit thickness and type of cavity gas used. |
| Whole Window Acoustic rating Rw, dB | Acoustic rating is laboratory tested to BS EN ISO 10140-2: 2010 (Airborne Sound Insulation). Window Acoustic ratings Rw 29 -39 dB. |
| Anticipated Life Expectancy | 60 years with the regular maintenance |
Product Specifications
| Material | Frame and sash in engineered redwood, bottom cill in solid hardwood (standard), engineered hardwood, Accoya, or European oak. |
| Finish | Three coat spray applied factory finish using water based micro-porous paint/ stain. |
| Colour | White - RAL 9016 - Standard. Any RAL - from RAL classic range. Stain - from TRC stain range. |
| Glazing | Double glazed, 4/16/4 Low-E top sash – 4 toughened/16/4 toughened bottom sash - Standard, Ug-value: 1.1 W/m²K; g-value: 0.52; |
| Perimeter spacing bars | White warm edge perimeter spacer with white warm edge integral spacers - standard. Silver and Black spacer optional. |
| Trickle ventilation | A controllable EA 2000, 4400mm².trickle ventilator can be fitted to the window dependant on width of frame. |
| Child restrictor | Angel lock standard. Traditional Sash Stop optional. |
| Operation | Sashes are hung on pre-tensioned constant force spiral balances. |
| Timber Species | Manufactured in selected engineered laminated pine, hardwood or Accoya, sourced from sustainable and managed forestry (FSC or PFEC certified). |
| Moisture Content | 12% +/- 2% on delivery |
| Glass | The windows to be factory fitted with 24-32mm thick sealed double-glazing unit Tested to BS EN1279. Composition of glass units is to be (from outside): 4mm float – 16mm argon filled cavity /4mm float glass with Low-E coating. Perimeter spacer in white or black. |
| Glazing Bars | Applied bars are used to achieve the slim section of traditional glazing bars. These are applied with double sided glazing tape to both faces of the sealed unit and capped with clear silicone. |
| Ironmongery | A lockable Fitch fastener and two finger pulls to the bottom sash with options in colour and finish. |
| Cill | Manufactured in Hardwood with options of Projections: 35 mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, 110mm. |
| Horns | Solid feature horns to top sashes are included as standard. |
| Ventilation | A controllable EA 2000, 4400mm².trickle ventilator can be fitted to the window dependant on width of frame. |
| Finish as Delivered | Window supplied factory finished, externally and internally with Teknos Water-based micro porous opaque to specified RAL colour, or stained finish. Aqua prime 1410, Aqua mid-2901, Aqua top 2600. |
| Restrictors | Restrictors which allow the opening of the sash to be restricted to 100mm is an option. |
| Fixing | Installation to be carried out using best building practices and in conjunction with recommendations of TRC windows. |
| Warranty | Manufacturing and Material Defects: 10-year guarantee. Finishes: The standard three-coat opaque finished joinery guaranteed for 10 years. The stain finishes guaranteed against blistering or flaking for six years. Seals: The seals on double-glazed units are guaranteed for 10 years (from the date of delivery). Ironmongery: Functional failure is guaranteed on ironmongery for two years. |
Technical Drawings
Whole window U-values as low as 1.4 W/m²K
Expected lifespan around 60 years with maintenance
Any RAL colour or TRC stain finishes available
10-year guarantees on glazing, finishes, and manufacturing defects
Timber from FSC or PEFC-certified sustainable sources
Sashes operate on pre-tensioned spiral balances
Browse completed installations showcasing TRC’s craftsmanship across a range of properties.
Modern spring sash windows operate in a smooth and seamless manner. By replacing the original cord with a spring-loaded mechanism, the windows are much easier to slim down. This enables sections of the frame to need less room for housing the extra reveal space (where the heavy weights and pulleys were once placed). This modern solution has become ideal for housing slimline window cavities.
Traditional and spring systems operate really well. The difficult part is which to choose?
Engineered to the highest standards, TRC spring sash windows exude quality and style. They take their blueprint from the traditional sash window, yet this modern alternative is the go-to choice for many architects and designers.
– Modern Spring Sash Design
– Slimline Timber Sash Windows
– Traditional Look, Compact Build
– Architect-Favoured Window Option
Spring sash windows incorporate a simple, compact and modern spring balance mechanism in place of weights and pulleys. The system works as a concealed balance system, with a tube fitted inside the window frame containing a spiral-shaped rod. This connects to a spiral window sash spring that’s adjusted according to the weight of the sash, and so balances the sash.
The spring sash offers a smooth operating experience, sliding up and down with ease, and will stay open at any point in the same way a traditional cord-and-weight sash window would.
Even though the spring sash window mechanism isn’t designed as a mechanical opening device, when opening the window, it provides assistance. In the down-and-locked position, the sash will remain tightly closed.
It’s simple to use as well as secure.
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