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External Walls - Do we now need an External Wall Coordinator?
- Oct 29, 2021
- Latest Journal
by Bernadette Barker BA (Hons) Dip Arch RIBA MSc (Construction Law & Arbitration) FCIArb DipICArb MIFireE
New roles within the construction industry are constantly evolving perhaps in part to the recognition of the increasing complexity and performance requirements of buildings both in construction and design.
In recent years external walls have become ever more complex and so has the legislation surrounding them that perhaps we now need to introduce the new role of an External Wall Coordinator?
Would the appointment of an External Wall Coordinator minimise the risk of errors in design and construction of the external wall?
The suggestion of the appointment of an External Wall Coordinator is not to detract from the role of the architect but to support the architect and recognise that external walls are becoming overly more complex and the design and construction of them needs to be carefully managed throughout the design and construction process.
Until recently there was actually no interpretation of an external wall under the Building Regulations.
Approved Documents B Fire Safety 2019 edition incorporating 2020 amendments -for use in England under Appendix A now describes the external wall of a building as:
‘The external wall of a building includes all of the following. Anything located within any space forming part of the wall.
Any decoration or other finish applied to an external (but not internal) surface forming part of the wall.
Any windows and doors in the wall.
Any part of a roof pitched at an angle of more than 70° to the horizontal if that part of the roof adjoins a space within the building to which persons have access, but not access only for the purposes of carrying out repairs or maintenance’.
For this article I will be talking about ‘built up’ walls, and not traditional cavity brick walls.
A built-up wall is constructed in a series of separate layers and there are numerous decisions to be made by the design team.
For an external wall you will generally have a backing wall, this could be block work, for example, or it could be an SFS (Steel Framing System).
You will also need amongst other components:
Insulation for thermal performance;
A vapour control layer;
A breather membrane;
You may or may not have a cavity within the wall as part of the design.
And if there is a cavity what cavity barriers are being used?
If services are running through the wall how will they be fire stopped?
If there is SFS you will need an internal lining.
An external layer.
Will the external layer be?
Or cladding? If so what type?
Or a rainscreen?
Or curtain walling?
Or perhaps there will be spandrel panels in the curtain walling?
A green wall? If so will it be synthetic or natural?
Windows and doors?
Services on or through the wall?
Attachments to the walls which can include, canopies, sun shading and brise soleil
And how high is the building?
However the wall is built up, between each and every one of these layers there are interfaces.
Although it may not appear to be, the external wall can be one of the most complex elements of a building with more or less every design team member requiring an input.
So have walls now become so demanding and complex that at times that we should appointing one individual to oversee the design and construction of the external wall element of the building throughout the life span of the development from conception to completion (and even possibly beyond when there may be complex maintenance regimes that need to be managed).
It is though actually most probably too big a role for one person.
Perhaps we need two External Wall Coordinators, one during the design stage and one during the construction stage?
The design of the external wall brings together all design disciplines which could include for :
• Acoustic Engineer;
• Drainage engineer;
• Facade engineer;
• Fire engineer;
• Structural Engineer;
• Mechanical and electrical engineers;
• Specialist contractors (s) may also be required.
Once the wall is designed, in an ideal world, to reduce coordination and interface issues between contractors, you would have one contractor responsible for constructing the whole external wall.
However, the wall is often broken up into subcontractor specialist packages some of which might be pre-fabricated off site and just craned in, for example balconies or sheathing boards.
So where can things can go wrong?
Consider even this simple scenario:
A contractor will tender for one of the specialist packages.
Trying to win the tender he may suggest an alternative product to the one he has been asked to price; the one that the whole design team has spent months agreeing will satisfy all of their design criteria.
But does the contractor understand why the product he was asked to price was chosen?
If he doesn’t understand, the wrong alternative proposed product can easily be suggested and it may not be compatible with other products it interfaces with or it may not have the required life span or required fire rating or acoustic performance or thermal performance or even all of them.
The proposed alternative product may seem, at first glance, suitable on reading the supplier’s marketing materials and literature, but drill down and you may find that, say a product has a claimed fire rating, this fire rating may only be suitable when the product is used under certain circumstances and in conjunction with other materials.
When selecting the proposed alternative products did anyone check that the test certificate (s) and see what for what use the product has been tested for? If it is stated that the product is only suitable for internal use it cannot be used in or an external wall.
But the contractor may not have looked at the ‘small print’ or even discussed with the manufacturer whether the product is suitable or not.
Proceed with an alternative product without checking with the design team it is suitable for its intended use and that is a very expensive mistake to rectify once the product is covered up.
With an External Wall Coordinator their remit might include for ensuring that any alternative product proposed is reviewed by all designers who had an input into the selection of that product.
New products are constantly being developed to solve evolving problems and manufacturers who have invested in developing products of course need to sell them and see a return on their investment.
Consider another example of where errors can occur: A labourer on a site may be fixing the cavity barriers and is under pressure to finish.
It may perhaps be getting dark, beginning to rain or he just has to finish by say 4pm to keep up with his program as he is anyway off to another site the next day.
The labourer takes the decision to speed things up by reducing the number of fixings by increasing the spacing between them.
He may not understand why the cavity barriers had to be fixed in a certain way.
Has anyone told him?
Is anyone checking?
If no one has checked the work you will now have cavity barriers that have not been installed correctly with the required number of fixings. The cavity barriers may then fail in the event of a fire.
With an External Wall Coordinator their remit might include for ensuring that QA/QC procedures are in place and that the installers are trained in the specific product or even ensure that the manufacturer’s representative comes to site to demonstrate how a product is installed.
To summarise, these are my outline views
• At design stage appoint an External Wall Coordinator;
• At design stage consider appointing a team member from each design team to coordinate with each other and the External Wall Coordinator;
• At construction stage appoint an External Wall Coordinator;
• At construction stage ensure that any proposed change to a product is advised to design team members and the External Wall Coordinator;
• Drill down and read the test information for any proposed product for the wall;
• Check the conditions under which the products were tested;
• Read the BBA (British Board of Agrément) Certificate and check for the installation requirements;
• Read all test certificates;
• Understand the products;
• Understand the interfaces between components of the external wall;
• Ensure the contractors and subcontractors and have a QA/QC procedure and that they are implemented;
• Ensure the installation teams are trained;
• Ensure the teams will coordinate and cooperate with each other;
• Make use of manufacturers’ CPD programs and help lines. They want to help and you and for to use their products;
• Where possible minimise the number of contractors responsible for constructing the external wall which will minimise the number of interface requirements twin contractors.
Bernadette Barker BA (Hons) Dip Arch RIBA MSc (Construction Law & Arbitration) FCIArb DipICArb MIFireE