Safeguarding integrity: Opting for the cheapest threatens a building’s performance

When it comes to architectural glazing in commercial buildings, the UK has some catching up to do compared with the USA and continental Europe, but this will only happen if specifiers and contractors stop judging products and systems on price above everything else. Experience shows that opting for the cheapest almost always results in problems for the future performance of buildings.

There are of course some shining lights in the UK industry who always put quality first, but how many times have we heard and read of the short cuts taken that have led to costly call backs and subsequent rectification work? No matter how impressive the building, if insufficient attention is paid to climatic effects, for example, it will begin to fail surprisingly quickly.

Whether it is because designers feel the matter is mundane or contractors are seeking to reduce costs, we have found that they are not evaluating correctly the crucial importance of basic protection in terms of sealing. Given that this forms a tiny fraction of the overall cost of the building, overlooking this aspect can verge on incompetence. Certainly it can be the basis of a costly legal action by a client when the building's defects become apparent.

This may seem like an over-dramatisation, but our experience shows otherwise. Poor protection, from inferior or poor sealing of roof, façade, window and door joints will lead to the damage of their integrity.

There really is no reason to accept poor performance given the quality there now exists from the design stage, to products and systems available, through to actual installation. For metalwork, there are now high performance sealants and ancillaries for joints in mullions, transoms, pressure plates and perimeter pointing. Complete weatherproofing for glass units and panels can be achieved by the correct application of systems incorporating gaskets, tapes and sealants.

Independent advice

There is independent and authoritative advice for our argument by the Centre for Window and Cladding Technology (CWCT). We would recommend strongly that designers and contractors follow existing standards and guides to good practice advocated by CWCT.

For example, in Section 4.8 of its Guide to Good Practice for Facades, CWCT advocates that extruded rubber gaskets should meet with the provisions of BS 4255 and that cellular gasket profiles must comply with ASTM-C509. The use of injection moulded corners in frame gaskets can improve significantly the performance of curtain wall systems.

Again, in the CWCT's guide, glazing gaskets comprising the weather seals of front-sealed curtain walls and those forming the air seals of secondary defence and rain screen pressure-equalised curtain walls, should be formed into complete frames with factory injection moulded vulcanised corner joints.

Simple steps

Simple steps in the design stage can prevent the horrors of water ingress from lack of sufficient drainage. We would recommend that all curtain wall and window systems be drained and/or vented to the exterior. Stopping water ingress requires the application of the Rain Screen Principle (RSP) in the design to achieve pressure equalisation (PE). RSP in this context is the design concept that prevents the penetration or wind driven water through that part of the curtain wall or window exposed to the exterior. PE makes the pressure in the glazing pocket the same as the external pressure ensuring water will not be drawn or sucked through the window or wall into the building.

But no matter how detailed design guidelines are followed, if installation is shoddy, all the best plans can literally go out the window. Unless basic steps are followed, the building's performance can be drastically affected.

To name just two procedures: All openings, joints and surfaces where materials are to be positioned, must be clean, dry and free of any foreign matter like oil, dust or grease. For example, all cleaning solvents should be wiped and not allowed to air dry; otherwise contaminants can remain on the substrate's surface.

Temporary protective coatings and films on metalwork must be removed before any application starts.

As I have said, the advice and products are already there in the UK. Changing attitudes to see all the potentialities may have to take a little longer.