The idea behind this solution is simple: the timber stays where appearance matters, and the face exposed to rain and sun is taken over by an aluminium capping.
In the room you see timber. From outside, the façade gets an aluminium surface, which does not need the same maintenance as bare timber.
About the product
Timber inside, aluminium outside
The structure of the window is laminated timber, just as in a classic timber window. An aluminium capping is fitted over the outer face, protecting the timber from the weather and from direct solar radiation.
For the cladding we use the Gutmann MIRA system. Gutmann is a German manufacturer of aluminium systems.
The solution is particularly suited to exposed façades and to buildings where periodic maintenance of timber joinery would be hard to arrange.
Benefits
What you gain from combining the two materials
Timber in the room
Inside, the timber remains, with its texture and its warmth.
Aluminium outside
The capping takes the exposure to rain, wind and solar radiation.
Gutmann MIRA system
The external aluminium cladding system we use for this version.
Low maintenance
The exposed face no longer needs the periodic work that bare timber requires.
Two finishes
Inside and outside can have different shades, chosen for the project.
Made to order
The dimensions and the configuration are settled for each job.
With a double rebate, a single rebate or an inclined rebate
Frame joints
Welded or with pressed corner cleats
Watertightness
Class 9A, a standard property declared by GUTMANN
Air permeability
Class 4, a standard property declared by GUTMANN
Wind resistance
C3 / B3, a standard property declared by GUTMANN
Operating forces
Class 1, a standard property declared by GUTMANN
Capping finish
Anodising or powder coating, in the same range as the rest of the aluminium joinery
Hardware
The one used in the construction of the timber window
Reference for declaration
EN 14351-1
The external cladding
The GUTMANN MIRA aluminium system
The aluminium capping is not a decoration laid over the timber: it is a system in its own right, with its own profiles, gaskets and fixing technique.
Construction
Types of construction
With a double rebate, a single rebate or an inclined rebate
Profiles
With a radiused visible edge or, for architectural requirements, in a square-edged version
Frame joints
Welded or with pressed corner cleats
Window shapes
All the usual opening types and shapes, including raking windows, semicircular, segmental and pointed arches
Build versions
A composite sash, a sash variant, or a construction with an inclined rebate
Values declared by the system manufacturer
Watertightness
Class 9A
Air permeability
Class 4
Wind resistance
C3 / B3
Operating forces
Class 1
How it works
The aluminium cappings fix to the timber section with the system’s own fixing technique, designed by the manufacturer for simple, economical assembly.
The available base heights allow different timber overlaps to be accommodated.
The wide range of gaskets covers the usual situations in use.
The mullion and transom profiles complete the profile joints and the junctions with the structure.
The hardware used in building the timber window remains usable.
The finish of the capping
The finish of the aluminium capping is chosen together with the rest of the aluminium joinery, from the same range of anodising and powder coating.
Reading the values correctly
The values above are standard properties, obtained by GUTMANN on a test element: a two-leaf tilt and turn French window with a mobile mullion, 2,200 × 2,200 mm.
The thermal test published by the manufacturer was carried out on an element of 1,230 × 1,480 mm, in spruce, with a timber construction depth of 88 mm, glass with a Ug of 0.6 W/m²K and a Thermix TX.N plus spacer.
None of these values is the transmittance of the finished window. Uw is established on the configuration ordered.
Timber systems
The construction depth
The depth of the profile is not a catalogue figure: it decides what glazing unit fits the rebate, how many sealing planes the sash has and how wide the frame reads in elevation.
68 mm construction
IV 68 · The profile we work with routinely
The classic section of the laminated timber window.
It is the reference construction of European timber joinery: 68 mm thick at the frame and at the sash. The rebate takes a double glazing unit, and the profile stays slim enough for buildings where the frame must not assert itself — refurbishments, holiday houses, buildings of architectural character.
Construction characteristics
Construction depth
68 mm at the frame and at the sash
Structure
Laminated timber, lamellae bonded in layers
Glazing unit
A double insulating unit; the rebate usually takes units of up to about 34–36 mm
Sealing planes
Two perimeter gaskets, usually in EPDM
Glazing
Glazing bead removable from inside
Where it fits
Refurbishments and heritage buildings, holiday houses, homes where the slimmest possible frame is wanted. It is also the base construction onto which the external aluminium cladding is fitted.
Worth remembering
The exact thickness of the glazing unit is confirmed on the profile ordered: the rebate differs from one moulding to another.
With double glazing, the 68 mm construction does not reach the thermal level of deeper constructions with triple glazing.
78 mm construction
IV 78 · The step up to triple glazing
Ten extra millimetres that change what fits in the rebate.
The difference from 68 mm is not just the extra timber but the rebate: at 78 mm a triple unit fits. That is where the thermal step comes from, because most of the area of a window is glass, not frame. At this depth class a third sealing plane is added as well.
Construction characteristics
Construction depth
78 mm at the frame and at the sash
Structure
Laminated timber, lamellae bonded in layers
Glazing unit
A triple insulating unit; the rebate usually takes units of about 40–44 mm
Sealing planes
Three perimeter gaskets
Glazing
Glazing bead removable from inside
Where it fits
New houses and refurbishments with a high thermal requirement, large windows, north-facing façades. It is the usual choice when the project calls for triple glazing.
Worth remembering
Triple glazing is noticeably heavier than double. The weight of the sash is calculated before the hardware and the hinges are fixed.
The third sealing plane has an acoustic effect too, but sound insulation comes from the glazing unit, not from the gaskets.
The profile we use routinely is the 68 mm one. The 78 mm construction is settled at design stage, together with the glazing unit: the rebate and the glazing thickness go together and cannot be chosen separately. The glazing thicknesses above are the usual ranges for each depth class and are confirmed on the profile ordered.
Glazing
Which glazing unit fits the rebate
In an ordinary window the glass takes up most of the area. That is why the choice of unit changes the result more than any other decision about the frame.
Ug ≈ 1,1 W/m²K
Double, with a low-E coating and argon
Two 4 mm panes, a 16 mm cavity, one low-E coating, argon fill
The 68 mm construction
Ug ≈ 1,0 W/m²K
Double, with a wider cavity
The same make-up, with the cavity widened to 18 mm
The 68 mm construction, if the rebate allows
Ug ≈ 0,6 W/m²K
Triple, with two low-E coatings
Three 4 mm panes, two 14–18 mm cavities, two low-E coatings, argon
The 78 mm construction
Ug can go below 0.6 W/m²K
Triple, with krypton in narrow cavities
The same make-up, with krypton instead of argon
When the unit has to stay slim
Ug is the declared value of the glazing unit, calculated to EN 673 by the manufacturer of the insulating unit. It is not the transmittance of the window: an installed window also has a frame and a spacer around the edge of the glass, and these change the result. The values above are the usual ones for those make-ups and are confirmed on the data sheet of the unit actually ordered.
Performance
How the values are established
We do not publish a Uw or Rw value for “the timber window”, because no such value exists outside a configuration. Below is exactly what each depends on and what we give you at quotation stage.
Uw — transmittance of the window
It is calculated to EN ISO 10077-1 from the transmittance of the frame, the transmittance of the glass, the thermal bridge around the edge of the glass and the areas of each. The same components give different values on a small window and on a large one, because the frame-to-glass ratio changes.
Uf — transmittance of the frame
It is calculated to EN ISO 10077-2, on the actual geometry of the profile. It depends on the construction depth, on the species and on the make-up of the section. A Uf value taken from another profile does not describe ours.
Ug — transmittance of the glass
It is declared by the manufacturer of the glazing unit, to EN 673. You receive it with the glass data sheet and it does not depend on the joinery.
Rw — sound insulation
It is determined by testing, to EN ISO 10140, and expressed to EN ISO 717-1. The result comes largely from the glazing unit: asymmetric thicknesses, acoustic interlayers and the width of the cavity count for more than the number of gaskets.
The tightness classes
Air, water and wind are classified by testing the assembled element, not the profile. The class is declared for the type of element tested and for the dimensions at which the test was carried out.
What you get from us
At quotation stage we settle the configuration: depth, glazing unit, spacer, hardware and dimensions. The declared values go into the project documentation, for the configuration ordered, not for a catalogue example.
Standards
How to read the classes
Windows and external doors are declared to EN 14351-1. The classes below are the scales from the standards: they show what a figure means, not what a particular product achieved.
EN 12207
Air permeability
How much air passes through the element at a given pressure difference. Class 4 is the tightest.
Class 1
Tested up to 50 Pa · permitted flow 12.50 m³/(h·m²)
Class 2
Tested up to 100 Pa · permitted flow 6.75 m³/(h·m²)
Class 3
Tested up to 300 Pa · permitted flow 2.25 m³/(h·m²)
Class 4
Tested up to 600 Pa · permitted flow 0.75 m³/(h·m²)
EN 12208
Watertightness
Up to what pressure the element keeps water out, under a continuous spray. The letter A means unprotected exposure.
Classes 1A – 4A
Tight up to 0, 50, 100 and 150 Pa respectively
Classes 5A – 7A
Tight up to 200, 250 and 300 Pa respectively
Classes 8A – 9A
Tight up to 450 and 600 Pa respectively
Class E
Over 600 Pa, with the test value declared explicitly
EN 12210
Wind resistance
What pressure the element withstands and how much it deflects under it. The class has two parts: the figure for pressure, the letter for deflection.
Classes 1 – 5
Test pressure 400, 800, 1200, 1600 and 2000 Pa respectively
Deflection A
Relative frontal deflection of no more than 1/150
Deflection B
Relative frontal deflection of no more than 1/200
Deflection C
Relative frontal deflection of no more than 1/300
The class is obtained by testing the assembled element and is valid for the type and the dimensions tested. It does not transfer automatically from one type of opening to another, nor from one size to another.
The material
Species and finishes
The species changes the grain, the weight and the behaviour outdoors. The finish decides how often you come back to the joinery.
Spruce
The species most used in laminated timber joinery: stable, light, with a quiet grain. It takes both stain and opaque finish well.
Pine
A more pronounced grain and visible knots. Chosen where a warm look with an evident texture is wanted.
Larch
Denser and more durable outdoors than spruce, with a warm natural shade. Suited to exposed façades.
Oak
A hard species, with a strong grain and great durability. The usual choice for entrance doors and for heritage buildings.
Meranti
A dimensionally stable tropical species, tolerant of moisture. Used on large elements and in severe exposures.
Ash
A grain close to oak, in a lighter shade. Chosen for interiors where the timber stays on show.
The finishing system
Impregnation
The first coat goes into the timber and protects it against blue-stain fungi and insects. It does not show in the final finish, but without it the remaining coats do not last.
Primer
It evens out absorption and gives the top coats something to key to. At corners and end grain it is applied more thickly, because that is where the timber draws in most.
Wood stain
A transparent or semi-transparent finish: the grain stays visible and the shade is adjusted through pigment. It is renewed periodically, according to exposure.
Opaque coating
An opaque finish, to a RAL or NCS code. It covers the grain, but gives a uniform surface and a complete colour palette.
Two-tone
Inside and outside can have different shades. It is settled before manufacture, because it changes the finishing sequence.
Maintenance
Timber left bare outside needs its finish coat renewing periodically. The interval depends on the orientation of the façade and on exposure, not on a fixed term.
Laminated timber is made from lamellae bonded in layers, with the grain alternating. The make-up reduces internal stresses, and the profile holds its geometry better than solid timber, particularly on long elements. The species above are those we use routinely on external joinery; other species are discussed project by project.
Hardware and fittings
Hardware
The clad window has the same timber construction inside, and therefore the same hardware as an IV68 window. The aluminium capping goes over it, without changing the mechanism.
Window handles
The same handle lines as on the timber window without external cladding: the aluminium capping changes nothing inside.
Roto Line
The classic handle line. The manufacturer describes it as having RAL-certified technology for long-term operation, with aluminium components.
Roto Swing
The second design line in the Roto range of handles for windows and balcony doors.
Roto Samba
A handle line with a more rounded design, for anyone who prefers a more discreet look.
The solutions the manufacturer offers for timber joinery. The load capacity of the hinge is calculated from the weight of the sash, which grows with triple glazing and with the aluminium capping.
Roto NX
The tilt and turn hardware system we use on timber joinery. The manufacturer offers it as a modular system, with Roto Sil corrosion protection in class 5 to DIN EN 1670 and certification to EN 13126-8, class H3 — 20,000 cycles.
Roto NX | T hinge
The standard surface-mounted hinge for timber windows, with a sash weight of up to 150 kg. In Roto’s nomenclature it is the surface-mounted hinge for timber, class H3.
Roto NX | Power Hinge
The version for heavy sashes: up to 200 kg on tilt and turn windows and up to 300 kg on bottom-hung-only ones. Still a surface-mounted hinge, still for timber.
Roto NX | TiltSafe
The components that let a window stay tilted without losing its burglar resistance: the manufacturer declares RC 2 in the tilted position.
For doors built in the same construction. The hardware belongs to the timber construction, not to the cladding: the aluminium capping goes over it, without changing the mechanism.
Roto Solid S | 117 NN
A two-part surface-mounted 3D hinge, for doors up to 160 kg, on a timber or PVC frame and sash. Lateral adjustment ±5 mm, height +4 / −1 mm and pressure ±0.75 mm, plus ±0.75 mm from the eccentric. CE marking to DIN EN 1935:2002, hinge class 12, SKG** certification.
Roto Solid S | 118 Z
The same capacity, with a pin that can be fitted from either direction — the version to choose when the space between the leaf and the head is small. Lateral adjustment +10 / −5 mm, height ±4 mm, pressure ±0.75 mm plus ±0.5 mm, overlap zone 12.5–27.5 mm. SKG** certification.
The cylindrical-roller version, declared by the manufacturer for timber, PVC and aluminium doors.
Roto Solid B | 218 P
A two-part cylindrical hinge, 18 mm in diameter, for timber, PVC or aluminium doors up to 80 kg. Lateral adjustment ±3 mm, height +4 / −2 mm, pressure ±1.5 mm. CE marking to DIN EN 1935:2002, class 11, ift QM 343 certification, 200,000 cycles, corrosion class 5 to DIN EN 1670.
Roto Solid B | 222 P
The same two-part construction, with a 22 mm roller, for doors up to 120 kg. Suitable for RC 2 burglar-resistant doors, with SKG** certification. CE marking class 13, ift QM 343, 200,000 cycles, corrosion class 5.
Roto Solid B | 318 P
The three-part version, with an 18 mm roller, for doors up to 120 kg. The third part spreads the load over a larger area. CE marking class 11, ift QM 343, 200,000 cycles, corrosion class 5.
Roto Solid B | 322 P
The top of the range: three parts and a 22 mm roller, for doors up to 160 kg. Suitable for RC 2 burglar-resistant doors, with SKG** certification. CE marking class 11 in the rebate or 12 face-fitted, ift QM 343, 200,000 cycles, corrosion class 5.
On this version we do not propose decorative fittings: the outer face is aluminium and the visual register of the window is a contemporary one. The handles are chosen from the current range.
Technical documentation
Do you need the technical sections?
The detail sections — head, centre and sill junctions — are not published on the site. We send them on request, for the configuration you are interested in.
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