Conforming the European directives the relevant fire safety requirements in the regulations have the following objectives:

• the capacity of structures during a given burn time guarantee
• the production and spread of flames and smoke limit
• the risk of spread of the fire to neighboring construction limit
• the attendees the chance to evacuate the building or to be helped
• take into account the safety of the intervention teams.
To meet these objectives, concerning wall cladding the following requirements are applicable:

• the fire stability
The standard fire shows a common known conventional fire-curve. These nominal curve does not depend on parameters that the actual fire in the fire compartment influence as the fire load, the ventilation conditions and the active fire prevention measures as sprinkler systems.
The standard fire curve (black) is shown, with different other nominal fire curves, in figure below. For comparison, also an arbitrary example of a natural fire curve (blue) is given.
A natural fire curve is a curve that is calculated on the basis of the main parameters that determine fire development in the compartment. A natural fire curve is characterized by its growth phase, heating phase and cooling phase. In the growth stage, the fire is still local. There exist many differences in temperature in the compartment.
In the transition from the growth phase to the phase of a real fire, the fire expands rapidly to the entire compartment. This is called the flash-over Read more


Though some sealants and adhesives may be used in similar circumstances, they are never used the same thing. The two are very different indeed.

  • Naturally, as its name suggests, sealants seals spaces that exist between one surface to the next. When a sealant is used the space becomes air and water tight.
  • Adhesives on the other hand are primarily used to bond materials together.

In common, sealants don’t usually have enough adhesion ability to hold two surfaces together. They are not used as primary bonding materials and are subject to creep under load.

These two products differ on several scales. The main differences between adhesives and sealants are strength, and other physical characteristics associated with strength. Generally, adhesives have Read more


In the Netherlands and Belgium a load-bearing structure made of treated wood is often used in a ventilated façade system.

However, the substances that are pressed into the wood are usually very toxic. Although there is sufficient supervision (certification) of the safety of employees in the production of treated wood, there is strangely enough no (or only very limited) control in the use (sawing) and waste phase of treated wood. This is despite the fact that, according to the European directive, impregnated wood in connection with the carcinogenic substances may not come into contact with human skin!

Copper II oxide and chromium trioxide (chromium VI) are often used in the preservation process. Chromium VI is extremely toxic to humans and is internationally known as a class 1 carcinogen. Used substances as tebuconazole and copper (II) carbonate-copper (II) hydroxide are not known as a carcinogen in Europe but in the USA known as a class 2B carcinogen.

This is why the use of treated wood is not permitted or unacceptable in many countries outside the Benelux. The use of treated wood of any kind is highly questionable because structurally very toxic, corrosive, environmentally hazardous and carcinogenic substances are used.

Finally, the one thing you must be extremely careful to never do with treated wood is burn it. Burning treated wood created toxic smoke that can be hazardous to health, so it is advised that treated wood be disposed of through normal waste collection services, unless it is a large amount of timber (where you will have to make arrangements with your council for it’s safe disposal).


Before you start with assembling two materials by means of an adhesive bond, the surfaces must be dry and properly cleaned and degreased first.

Always assume that the surface to be bonded is contaminated and therefore clean both surfaces with TWEHA Cleaner+ and a cloth. TWEHA Cleaner+ is a bonded-cladding-detergent based on Isopropyl alcohol.
Always use a lint-free, non-coloured cloth that does not contain any additives, contaminants or polishes. Clean by rubbing in only one direction, otherwise the contamination on the fabric may end up on the surface again. Never use a cloth several times.
Do not touch the cleaned surface with your fingers again, otherwise skin grease will be on the surface again.
Never use thinner or a gasoline based liquid for degreasing! These are so-called petroleum derivatives and these only make the subsurface more greasy!

If needed roughening ensures that the adhesive can flow in a roughened surface. This increases the adhesion surface and creates a better connection.
Note: the adhesive layer of THEHA Tape will not flow, so when roughening a smaller adhesive surface is created, so, in case of an aluminum framework, never roughen the surface!

Fiber cement: Loose fibers and cement granules
HPL: residue of protective film
Natural stone: sludge or residue from sawing process.
Tiles / ceramics: Cleaners and moisture
Metal: Oil, grease, rust and moisture
Glass: Fingerprints, silicones and moisture
Plastic: Release agents, dust and plasticizers
Rubber: Talc, grease and plasticizers


Before starting check with a peel-of test.


Easily calculate the exact quantity of bonding material required for your project construction by using our free quantity calculator.

The TWEHA Calculator estimates the exact quantity of TWEHA Adhesives required for your building envelope project. It also estimates the number of rolls of TWEHA Tape, the quantity of TWEHA Cleaner+ and other TWEHA products necessary based on standard 600 mm centre-to-centre distance of your substructure. Purchasing slightly more material than the estimated result can reduce the probability of having insufficient resources.