Façade Principles Notes
Introduction to Façade Principles
The book Façades – Principles of Construction aims to provide architects and students with a fundamental understanding of façade design principles, basic systems, construction aspects, structural integration, and technical realization.
It moves beyond specific façade variations or current regulations, focusing on enabling readers to analyze projects and develop technically sound solutions.
The architectural design should include the concept, space composition, building organization, and structural realization.
Surface materials and their application express the building as a whole, making detail a crucial element of the architectural concept.
The architect needs creative control over every element, or it might influence the architectural expression contrary to its original conception.
The book provides an overview of typical solutions and functionalities to enable architects to be competent partners in façade design and understand system suitability and limits.
The façade is not seen as an isolated component but as an integral element affecting appearance, loadbearing, environmental control, and creative expression.
Façade Planning and Construction
Façades influence the space within and around the building, impacting views, lighting, ventilation, user comfort, building services, and loadbearing.
Façades are integral to building design, use, structure, and services, influencing the entire design and construction process.
Designing a façade involves communication and decision-making through initial conception, functionality definition, design, implementation coordination, and assembly.
Processes like feedback on design and functionality, and element importance within the building's structure should occur throughout all phases.
Example: To keep water out, a design might include an overhanging roof with recessed windows and a layered construction method with drainage; assembly would proceed from bottom to top to ensure overhangs and sealing.
A transparent envelope could entail a non-loadbearing façade with a movable joint to avoid stress on the glass façade from the main structure.
Evolution of Façade Technology
Early Modern Architecture featured technically simple detail solutions, but today's buildings involve complex, interlinked technical solutions.
Modern façades are complex structures with numerous functions and complex technical realization, driven by increased demands for comfort such as heat-insulation, air- and rain-tightness.
This leads to thermal separation of construction profiles and complex jointing technology.
Development Trend Complexity
The prevailing trend involves increasing complexity, with 'intelligent' façades developed to increase user comfort.
The actual practicality of these technologies remains partially unanswered, with some developments being revised or disappearing.
Double façades, though built in quantities, suffered from flawed designs or incorrect use, damaging their reputation.
Proprietary technologies and systems have historical predecessors like the Mediterranean box-window or decentralised air-conditioning units.
Current Topics in Façade Technology
Current topics include energy, user comfort, individual façade expression, and adaptation of existing façades, driven by the search for new solutions to create façades for varying functions, climatic circumstances, and geographic locations.
Two major trends are expected: further technical developments with improved design tools, manufacturing methods, and system variants, and simplifying the façade by integrating components and functions.
Façades result from individual creative conceptions, designed for a specific place, context, and architectural concept.
Façade planning is an integral part of the design process that employs constant feedback and is based on progressive steps.
Book Structure
The book is structured as follows:
'From Wall to Façade' discusses the development of today’s façades and their typological classification.
'Principles of Construction' explains the interrelationship between the building structure and the façade system.
'Detailing and Tolerances' broaches the issue of generating technical details for the general solutions defined previously.
'Climate and Energy' discusses integrated design and building structure aspects of the façade.
'Adaptive Façades' analyses how façades can adapt to changing parameters.
'Case Studies' describes typical and special façade solutions on the basis of selected projects.
Four new, exemplary case studies were selected for this second and revised edition. They explain four different construction methods that are in common use; particularities are noted in the text. The case studies are meant to be transfered to a particular project or problem.
The rear-ventilated façade of the Concept House in Rotterdam, the Netherlands, is an interesting example of façade cladding that could be similarly realised with many different materials in sheet or panel form.
The second case study, the State Archive Nordrhein-Westfalen in Duisburg, Germany, deals with a more traditional single-skin solid masonry construction, which is particularly helpful as an example for extensions to older buildings or restoration of historic buildings. Both examples are wall constructions with windows, and therefore so-called punctuated façades.
The transparency and façades with large glazed areas is addressed with the other two case studies. The new building for the Department for Architecture and Interior Design at the University of Applied Sciences in Detmold, Germany, was executed with a post-and-beam façade; a suitable solution for buildings only a few storeys high.
The element façade of the Headquarters Süddeutscher Verlag in Munich is a good example of a very modern high-rise façade, delivered as prefabricated elements and assembled storey by storey. Following the punctuated façades of the examples in Rotterdam and Duisburg with their loadbearing walls, these two curtain wall variants offer an informative introduction into the design of façades which are placed in front of the loadbearing structure of the building.
The authors offer an outlook on the future of façade technology and the possible lines of development.
Solid Wall Construction
Solid wall constructions are preferred in cold climates and settled populations, built from readily available materials or elements processed for the purpose.
The objective is to build a wall that withstands climatic influences while keeping the building method uncomplicated.
Present-day solid walls use structural units with loadbearing and thermal insulation properties, but the basic principle remains unchanged.
Warm vs. Cold Façades
Warm Façades:
Insulating layer is mounted directly on the outside or inside of the façade construction.
If the insulating layer is applied on the outside, it must be water-resistant.
If the insulating layer is on the inside, the solid wall's heat storage ability will no longer influence the interior environment.
Cold Façades:
Insulating layer is separated from the climatic protection layer by a layer of air.
This allows the insulating layer to dry out if water penetrates.
Historical Development of Walls and Façades
The form and function of present-day wall and façade constructions result from a long process of development related to human history.
Two original basic forms of human existence: settled and nomadic.
Two different basic principles for constructing the outer envelope: solid walls fixed to one spot and more flexible façades like tents for mobile use.
The development described here follows construction trends against a background of structural and functional relationships.
The current overview is a snapshot from current perspectives, focusing on present-day developments.
Openings in Solid Wall Construction
Openings were made in walls to allow smoke to escape and later enlarged to let light in.
Horizontal beams were used as lintels to solve the problem of weakening the wall fabric.
In Gothic architecture, the amount of solid masonry was reduced to allow large glass areas, using impressive constructive techniques.
Dissolution of Masonry
Driven by the desire to admit more light, the amount of masonry was gradually reduced.
Gothic architecture replaced monolithic walls with filigree structures, precursors to present-day skeletons.
Roofs were shell constructions with cross-wise support, resting on pillars and loadbearing walls.
Vertical forces were concentrated at predetermined positions, transferred to the ground, creating large openings in unstressed parts of the walls.
Lateral forces were transferred to the ground using ties or external buttresses.
Bridging the Gap
Window lintels reached their structural limits, leading to the use of arches.
Gothic architecture used pointed arches, more capable of bearing the weight of the wall above.
Present-day styles use lintels of steel or reinforced concrete to span openings.
Closing Apertures – Single Glazing
Apertures were filled with translucent materials, then with single panes of glass.
Glass provided natural lighting and allowed views out.
Initially, small panes were used due to production technology limitations.
Development of the glass-in-lead technique allowed construction of larger windows.
Box Window
A second pane of glass is added, slightly set back, to create an additional climatic buffer.
The space between panes is not hermetically sealed to avoid condensation.
This is the first intelligent wall: the second window pane can be adjusted depending on the weather or occupant’s needs.
Insulated Glazing
Insulated glazing consists of two panes of glass permanently joined with an insulating layer of air or inert gas in between.
Panes are usually mounted in aluminium or plastic profiles with a silicone sealant.
Walls with Skeletal Structure
Half-Timbered Construction
The developments of dissolving the solid wall and the tent combined to transform the solid wall into a lightweight modern façade.
A supporting frame or skeleton (originally of timber) is built and infilled with appropriate cladding.
The European predecessor is half-timbered construction, with a timber skeleton and infilling of interlaced branches, mud, clay, or bricks.
Successive stories are mounted either in the wall or resting on the wall.
Timber-Frame Construction
The American variant consists of bearing timber members infilled with sheets of wood products.
It has poor thermal buffering properties.
Distinction between platform frames and balloon frames.
Balloon Frames: Ceiling of one storey and floor of the next are mounted in the wall.
Platform Frames: They rest on the wall.
Resolution of the Wall
Neoclassical architects separated the outer envelope from the loadbearing structure.
The bearing function is provided by columns enveloped into the interior.
Bearing, sealing, and transmission of light became more clearly distinguished from one another.
Post-and-Beam Façade
The post-and-beam façade is the next step in the dissolution of the solid outer wall.
It consists of storey-high posts linked by horizontal beams.
The gaps between posts and beams perform functions like cladding, lighting, and ventilation.
The posts transfer wind forces and self-weight to the ground and support cladding.
Post and Beam Systems
Apart from pure post-and-beam systems, post systems and beam systems have been developed.
The objective is to increase openness and transparency.
In post systems, the structural limit is determined by the maximum permissible distance between posts.
Beam systems use tie rods to bear loads.
Beam Façade
When construction is reduced to using only beams, the result is a suspended system where loadbearing capacity comes from above.
Heavy-duty tie-rod structures are mounted near the roof to bear the façade's weight.
The beams only have to resist lateral forces.
Curtain Wall
Systems where the façade hangs from the front of the roof are precursors to curtain walls.
The construction is independent of the building’s main loadbearing structure.
The façade can be partitioned almost at will, using cladding or glazing.
Vertical and lateral loads are led to the ground floor by floor, with special loadbearing elements added to bridge longer spans.
System Façade
Curtain walls may be divided into stick and unit systems.
Elements of the wall can be prefabricated and assembled on site or the entire system wall can be prefabricated off-site and installed as a whole.
Advantages include guaranteed production quality, rapid assembly, and low labour requirements on site.
Unitised systems are established in high-rise façades, mounted from the storey above with a crane.
Double Façades
Double Façades are a result of the shift of various functions related to the interior functions of the building immediately behind the façade.
Ventilation can be provided by thermal insulation between the two layers of the façade.
The initial euphoria has been replaced by a pragmatic approach.
Double façades are used when called for, such as in high noise levels, high wind loads, or increased building height.
Types of Double Façades
Second-Skin Façade:
A second layer of glass is added over the entire outer surface of the building.
Advantages: technical and structural simplicity.
Disadvantages: limited control possibilities and risk of overheating.
Box-Window Façade:
Storey-high façade elements are included, which individual users can open at the top and bottom.
Advantages: freedom for individual occupants to control their internal environment.
Disadvantages: freedom given to one occupant may have an adverse effect on others, such as exhaust air from one floor influencing incoming air on the floor below.
Corridor Façade:
Horizontal baffles are used at ceiling height in the space between the two skins.
Advantages: can be naturally ventilated from all directions.
Disadvantages: potential noise interference between neighbouring rooms.
Shaft-Box Façade:
Discrete box windows release their exhaust air into a vertical shaft mounted on the façade, extending over several floors.
Advantages: effective due to stack effect.
Disadvantages: requires complex installation and control-engineering effort.
Alternating Façade
Also known as hybrid façades.
Single-skin façade constructions that can be converted locally to double façades by adding a second skin.
Objective: combine the benefits of the simplicity of the single-skin façade with the buffering effect of the double façade.
In summer, ventilation takes place via the single skin area.
In winter, the double-skin area is used for ventilation by using warmed up air from the cavity.
Integrated Façade
Functions other than ventilation, such as air-conditioning or control of lighting levels, are integrated in the façade.
Also called a modular façade or hybrid façade.
Offers the possibility of divesting the building itself of all functions apart from bearing its self-weight.
Incorporates the enclosure function and all environmental-engineering functions within the façade.
Some essential functions are transferred from the core to the façade.
The Polyvalent Wall
Developed by Mike Davies, the concept involves a façade that, apart from sealing and insulation, can also assume other functions such as environmental control, ventilation, and individual control of lighting.
A sensible philosophy would be the separation of functions into various levels and their incorporation within various building components, which are then ultimately combined in the modular façade.