Pre-patinated copper facade, Plaza del Rey, Burgos (caption)
Here we will briefly look at the possibilities for constructing the facade and the potential systems.
All Quinta Metálica® facades are built by installing several layers of different materials on top of each other, where each layer has its own particular function. If we start from the outside, moving inwards, we have the following generic layers.
- Metal – waterproofs and protects the facade, provides the aesthetics.
- Separating plate/ventilation membrane - helps metal to dilate, can help to protect the facade against condensation, can absorb small irregularities in the direct support, can provide micro-ventilation under the metal
- Direct support – supports the metal and the fastening base
- Air plate (ventilation chamber) – prevents condensation in ventilated facades.
- Thermal insulation – insulates the inside from the cold and the outside heat
- Vapour barrier - prevents condensation on non ventilated facades
- Structural support – supports all the previous layers, resists wind forces
Layers in detail
Separator plate / ventilation membrane
This membrane makes it easier for the panelling to dilate (in response to thermal changes) because it provides a surface over which the metal can easily slide. Quinta Metálica uses breathable membranes because they provide both functions effectively and they also help to protect the facade against condensation, trapping the water between it and the inside of the metal, until it drains down towards the start of the facade or evaporates. For zinc and lead facades, Quinta Metálica always installs a ventilation membrane because it lets the inside of the metal breathe, preventing the condensed water from making contact with the zinc, prolonging the metal's useful life.
Direct support for seam and butt joint facades
The systems to cover a facade that we use most often – the seam and the butt joint - are made with thin metal plates and therefore require direct support (the support immediately below the metal) that stretches over the whole or almost whole metal surface. This support withstands all the forces transferred from the panelling to the main structure.
The support has to be reasonably smooth and regular, as any appreciable defect will be transmitted through the covering and will be visible, giving the facade poorer quality.
- The most usual support is the 19 mm water repellent boardIt is economical, easy to cut and install, resistant, long lasting and does not resist the screws to fasten the panelling. For curved facades, it can be used in narrow strips. The board planks are supported with a metal or wooden batten every 600mm, properly levelled.
- Pine decking treated in autoclave, with an imprint between strips, provides a good support. It is used above all for zinc facades to assure good ventilation of the inside of the metal.
- The corrugated galvanised steel sheet provides a light and economical support. It is fixed with the wide side up, to give greater support surface area to the outer metal, and with the corrugation dip in the opposite direction to the joints. It is supported with metal battens, ideally every metre.
- The rigid thermal insulating boards form a very practical base on non ventilated facades and eliminate the cost and weight of the board or the corrugated sheet. In this case, the screws fastening the panelling cross pieces go through the insulation and are anchored on the roof's structural support.
- Sandwich panels are also used, taking into account that the minimum thickness for the outside is 19mm for wood, 0.8mm for steel.
Direct support for panel facades
If the facade is going to be produced in the facade panel system or in cassette panels, the support is not continuous as we make the most of the fact that the panels in both systems are self-supporting. In these cases, the support is composed of metal battens, with spacing of around 600mm. For cassette panel covering, they will always be fitted vertically, but for tongue and groove joint facade panels, we fit them in the opposite direction to fitting panels, that can be fixed horizontally or vertically.
Not all support materials are suitable for each metal – see the pages for each metal to obtain a list of correct materials.
Neither the type of insulation chosen for the roof nor its thickness has any influence on the panelling. Only in the event that the insulation provides direct support for the metal must it meet a specific requirement - it must withstand temperatures of 80ºC without being damaged.
Thermal design – ventilated and non ventilated facade
The top layers described above can be interspersed to give two types of facade – the ventilated facade and the non ventilated facade. Quinta Metálica makes both versions.
The metal facade and condensation
The basic problem for a metal facade is that we have a vapour barrier exactly where we don't want it – on the cold side of the facade. If we do not design the facade carefully, it can produce significant quantities of condensation that will damage the building and its contents. This is particularly important when the humidity inside the building is high – swimming pools, gymnasiums, kitchens, etc. or the building is located in an area with very cold winters.
To prevent this happening, Quinta Metálica provides two different solutions: the ventilated facade and the non ventilated facade.
The ventilated facade
This solution protects the facade from condensation by carrying the damp air (from inside the building) outside by means of a moving air sheet. This air sheet runs in front of the insulation (between the insulation and the direct support that supports the covering) and goes continuously from its air inlet at the start of the facade to its outlet on the top. In Spain there are no rules to restrict the size of this chamber but based on our own experience and the rules in other countries, we recommend a chamber height of between 20 and 30mm. Contact Quinta Metálica for more information.
This plate is built with vertical metal battens (or vertical wooden bars) that have a height equivalent to the thickness of the thermal insulation required, plus an additional 20 to 30mm to create the chamber. The details that Quinta Metálica uses make sure that the air inlet at the start and the outlet on the coronation are large enough to generate appropriate ventilation.
The non ventilated facade
This solution protects the facade from condensation by fitting a vapour barrier below the thermal insulation. This barrier has the function of eliminating the possibility of filtrations of damp air from inside the building through the insulation towards the cold parts of the roof and condensing. Its correct operation is fundamental so in our opinion it is important that it has a continuous support that makes it easier to fit and seal its joints perfectly. In this roof solution, there is no air chamber.
Which solution should we apply?
The ventilated facade works well in Spain with all metals. This is compulsory when we are panelling with zinc or lead. It is suitable for all facades, eliminates thermal bridges in the intersection with the ironwork and dissipates heat in the summer. Panel systems are almost always ventilated.
However, when the additional cost to ventilate the facade is significant, when the total thickness of the facade is very limited, or when the facade has many windows and its ventilation will not be particularly practical, the non ventilated facade with its vapour barrier will be the best option.
To get technical evaluation for your project facade's thermal design, please contact Quinta Metalica and we will help you to design your facade properly.
Examples of building facades:
Ventilated facade with seam on breathable sheet on corrugated sheet on structural plates filled with insulation.
Ventilated facade with seam on breathable sheet on board on metal profiling, insulation between profiles.
Ventilated facade with butt joint on breathable sheet on board on insulation panel, insulation between insulation panels.
Ventilated facade with facade panels on metal profiling anchored to the wall, insulation between profiles.
The crimped systems that we use on the facade are seam and butt joint and the panel systems are tongue and groove joints facade panels and cassette panels. The seam and butt joint systems, due to being cheap and flexible, are far and away the most used by Quinta Metálica.
Choosing the system
The panelling system is usually chosen according to two criteria - economics and aesthetics.
Looking at the question of costs first, and taking into account that each site is different and its characteristics and the metal used influence the calculation, panel systems can cost between 20 and 50% more than the crimped systems. To get an accurate estimation, we recommend that you contact us and after technical evaluation, we will provide you with a quote without commitment for the most appropriate systems.
As far as aesthetic considerations are concerned, the best way of comparing is to consult photographs of works carried out using each system and decide which fits best in each project. In any case, the following comments are summarised in the table below.
Summary of the system
||Plates crimped along their length with rib shaped joint, flexible
||Direction, craftsmanship, character
||All except lead
||Metal sheets fitted on all four sides with overlapping joint, very flexible
||Discreet, craft texture
||All except lead
|Tongue and groove joint panels
||Narrow panels fitted together, imprint joint, hidden fastening
||All except lead
||Large panels with imprint joint, fastening on view, semi-hidden or hidden
||Formal, powerful, solid
||All, although some copper and zinc finishes do not make sense given their limited maximum width - please ask Quinta Metálica.
For more information on each system, please refer to the files for each of them.
Workshop Building in Calle Trole, Vallecas, Madrid. Facade with vertical seam (caption)
In all the aforementioned systems except for the tongue and groove joint panels, installation starts in the lower part of the facade, fitting the start piece and fastening strips. Here we pay particular attention to these elements as they form the lower contour of the facade.
The fastening strips or side pieces required to install the lateral end pieces on the facade are fastened next.
The facade elements can then be fitted. We make sure that they are correctly aligned and positioned in accordance with the facade exploded drawing. In finishes that have different shades from sheet to sheet, we try to make a random distribution.
We then finish the facade by installing the end pieces around the windows, curtain wall, doors, ventilation grills, etc.
Throughout this whole process we try to make sure that:
- the edges of the facade are straight, clean, pure and light
- the facade dilates correctly
- the details are executed carefully
- the same type of detail is performed in the same way all over the facade
- the exploded drawing for the elements is aesthetically correct, particularly taking into account the position of the windows and doors
- the covering is dent-free and the elements are as flat as possible
- the overall aspect blends in with the rest of the building and provides added value to the work
We take it for granted that the facade with be waterproof and will protect the building for decades from everything the weather has to throw at it.
Regional Animal Health Laboratory, Villaquilambre. Pre-patinated zinc facade (caption)
Request for information
For technical consultancy on your project, please contact Quinta Metalica and we will be happy to help you.