Choosing the Right Airtight Tape
Airtightness relies on creating a continuous sealed layer around the building envelope.
Membranes and boards form the main airtight or windtight layers, while specialist tapes and adhesives are used to connect overlaps, edges, penetrations and junctions.
The correct tape depends on the location, substrate, shape of the junction and whether the connection is internal or external.
Airtightness vs Vapour Control
Airtightness and vapour control are related but they are not the same thing.
An airtight layer controls the movement of air through gaps and cracks in the building fabric.
A vapour control layer influences the diffusion of water vapour through the construction.
A membrane can perform both functions, but only if its overlaps, edges and penetrations are sealed correctly.
This is why tapes and connection products are an essential part of a complete airtightness system.
Pro Clima TESCON VANA
TESCON VANA is a versatile all-round adhesive tape for internal and external airtight and windtight connections.
It can be used for sealing membrane overlaps, edges and connections to suitable building surfaces and is particularly useful where one general-purpose tape is required across several details.
As with all adhesive tapes, the substrate needs to be sound, sufficiently clean and suitable for bonding.
Porous, dusty or difficult surfaces may require appropriate preparation or primer.
TESCON No.1
TESCON No.1 is another flexible airtight sealing tape used for membrane overlaps, edges, junctions and penetrations.
It can be used with airtight membranes internally and windtight membranes externally where the substrate and application are appropriate.
The flexibility of the backing allows it to conform around many common construction details.
UNI TAPE
Pro Clima UNI TAPE is designed principally for internal airtightness applications.
It can be used for sealing suitable internal airtight membranes and airtight wood-based boards.
Because it is an internal tape, it should not automatically be substituted for external tapes designed for long-term exposure to weather and moisture.
DUPLEX Double-Sided Tape
Pro Clima DUPLEX is a double-sided adhesive tape suitable for selected internal and external applications.
It is particularly useful for fixing and connecting membranes to smooth surfaces and for securing membrane overlaps during installation.
Double-sided tapes can also help hold membranes in position before subsequent battens or construction layers are installed.
Window & Door Airtightness
Windows and doors create some of the most important junctions within an airtight building envelope.
The connection between the frame, wall and airtight membrane needs to remain continuous even where different materials meet.
Specialist window tapes are designed to simplify these transitions and can often be plastered over to create a clean connection between the window frame and internal or external finish.
CONTEGA SOLIDO SL
CONTEGA SOLIDO SL is an internal airtight window and junction tape designed for full-surface adhesion.
It can be used to form airtight connections between windows, doors, membranes and suitable masonry or mineral surfaces.
Its fleece surface can be plastered over, allowing the tape to become integrated into the internal plaster finish.
This makes it particularly useful where windows are being installed into masonry walls that will subsequently receive lime or mineral plaster.
CONTEGA SOLIDO EXO
CONTEGA SOLIDO EXO is designed for the exterior side of window and door junctions.
It provides a windtight connection designed to resist exposure to driving rain while maintaining the appropriate external connection between the frame and surrounding construction.
It should therefore not be confused with CONTEGA SOLIDO SL, which is intended for the internal airtight side of the junction.
Internal & External Window Sealing
A well-designed window detail generally considers the internal and external junction separately.
Internally, the priority is maintaining the airtight layer.
Externally, the connection needs to maintain windtightness and weather protection while fitting into the drying strategy of the complete wall.
Using the correct internal and external products is therefore preferable to assuming that one generic tape is suitable for every side of a window.
TESCON PROFIL for Corners
TESCON PROFIL is specifically designed for corners and angled junctions.
Its divided release backing allows different sections of the adhesive surface to be exposed separately, making it easier to form controlled connections around corners, windows, doors and other changes in plane.
This can be particularly useful where an ordinary flat tape would be difficult to position accurately.
EXTOSEAL ENCORS
EXTOSEAL ENCORS is designed for moisture-exposed sealing details where water needs to be safely managed.
Typical applications include window sill and sub-sill detailing, window connections and selected junctions involving wood fibre boards and adjoining building components.
It should therefore be distinguished from MAGOV, whose principal role is highly flexible airtight sealing around penetrations and complex junctions.
Nail & Screw Penetrations
External membranes and wood fibre boards are often penetrated by screws or nails when counter battens and other components are installed.
These penetrations can compromise the weather-resisting layer if they are not detailed correctly.
Specialist nail-sealing products are designed to seal around the fixing as it passes through the membrane or board.
TESCON NAIDECK
TESCON NAIDECK is a double-sided nail-sealing tape used beneath counter battens in suitable roof constructions.
Its sealing material is designed to close around nail and screw penetrations and help maintain the integrity of the underlying weather-resisting layer.
It should be used as part of the appropriate roof or façade specification rather than as a general-purpose membrane tape.
Rough & Porous Substrates
Not every surface provides an ideal background for self-adhesive tape.
Old timber, masonry, plaster, concrete and wood fibre can be dusty, porous or uneven.
These backgrounds may require a compatible primer or adhesive connection product rather than relying solely on direct tape adhesion.
Good substrate preparation is fundamental to the durability of the completed airtight connection.
TESCON SPRIMER
TESCON SPRIMER is a spray-applied primer used to prepare and stabilise selected substrates before applying Pro Clima tapes.
It can be useful on materials such as wood, wood fibre, masonry and concrete where additional surface preparation is required.
Primer should not automatically be applied everywhere; its use depends on the substrate and the requirements of the particular tape.
ORCON Adhesive Connections
Products such as ORCON F and ORCON MULTIBOND are adhesive sealing products rather than conventional tapes.
They are particularly useful for connecting airtight and vapour-control membranes to rough or mineral surfaces such as masonry, plaster, concrete and rough timber.
These products complement the tape range where a normal self-adhesive tape is not the most appropriate way to form the connection.
Service Penetrations
Pipes, cables and ducts create common weak points in airtight construction.
The airtight layer needs to remain continuous around each penetration.
Flexible tapes and specialist sealing products can be used to form these details, but the correct product depends on the size and shape of the penetration and the surrounding membrane or substrate.
The detail should allow for any expected movement rather than relying on a rigid patch around a moving service.
Airtightness & Wood Fibre Insulation
Wood fibre insulation systems are often designed as part of a vapour-open construction, but vapour openness does not remove the need for airtightness.
In roofs and framed walls, uncontrolled air leakage can transport significantly more moisture into a construction than vapour diffusion alone.
Careful sealing of membranes, board joints, service penetrations and wall-to-roof junctions is therefore particularly important.
Airtightness in Traditional Buildings
Airtightness improvements can also be useful in traditional and historic buildings when they are carefully designed.
The objective should not be to make the building indiscriminately vapour resistant.
Instead, airtightness can reduce uncontrolled draughts and air leakage while compatible membranes and materials are used to maintain appropriate drying potential.
The complete wall, roof or floor build-up should therefore be considered rather than choosing a tape or membrane in isolation.
Preparing Surfaces for Airtight Tape
Before applying tape, surfaces should generally be sound, stable and free from excessive dust, grease and loose material.
Very porous or friable surfaces may require appropriate primer or another connection method.
Tapes should also be rubbed firmly into position to establish good contact with the substrate.
Poor installation can undermine the performance of even a high-quality tape.
Frequently Asked Questions
What tape should I use for airtight membrane overlaps?
A general airtight tape such as TESCON VANA or TESCON No.1 can be suitable for many membrane-overlap applications.
The exact choice depends on whether the detail is internal or external and on the membrane and substrate being connected.
What tape should I use around windows internally?
CONTEGA SOLIDO SL can be used for internal airtight window and door connections to appropriate masonry and other substrates.
What tape should I use around windows externally?
CONTEGA SOLIDO EXO is designed for exterior windtight and weather-resistant window and door connections.
What tape is best for corners?
TESCON PROFIL is specifically designed for corners and angled junctions and has separate release strips to simplify installation.
What is EXTOSEAL ENCORS used for?
EXTOSEAL ENCORS is primarily used for moisture-exposed connection details such as window sills, sub-sills and selected external junctions.
What is TESCON NAIDECK used for?
TESCON NAIDECK is a nail-sealing tape used beneath counter battens to help seal nail and screw penetrations through suitable roof membranes and related layers.
Do I need primer before applying airtight tape?
Not always.
Smooth, clean and suitable substrates may allow direct bonding, while porous, dusty or difficult backgrounds may require a compatible primer such as TESCON SPRIMER.
Are airtight tapes breathable?
Airtightness and vapour permeability describe different properties.
The tape is used to stop air leakage at a joint. The vapour behaviour of the overall construction depends principally on the membranes, insulation, boards and other layers within the build-up.
Can Roundtower help choose the correct tape?
Yes.
If you provide details or photographs of the junction, membrane and substrate, Roundtower Lime can help identify the appropriate tape, primer or adhesive sealing product.
Need Help with Airtightness Detailing?
If you are unsure which tape is required for a membrane overlap, window, door, roof, corner, floor junction or service penetration, contact Roundtower Lime with details of the construction.
Our technical team can help identify the appropriate Pro Clima tape and associated preparation or sealing products for the detail.
