Category Archives: Construction Detail

Why would I need a bat survey?

Did you know that the UK has 18 known species of bat and that they are a protected throughout Great Britain and Europe?   The UK Wildlife and Countryside Act 1981 (as amended) and EU Conservation of Habitats and Species Regulations 2010 lists protected bats among other fauna and flora.   It is, therefore, a criminal offense to harm or disturb bats or their habitat.   Natural England and The Bat Conservation Trust provide support, guidance and licensing towards their protection.

National and local planning policy include guidance towards the protection and enhancement of all biodiversity.   Town planners are required to consider any legally protected species as a material consideration when assessing development proposal that may harm a protected species or its habitat.

Professional ecologists can be employed to help develop design proposals for the built environment and are able to provide the necessary support for planning applications through survey and mitigation.

Proper assessment of existing buildings and other potential habitats for bats is crucial in design development prior to submitting a planning application.   For bats, initial assessment can take place at any time of the year.   A trained ecologist will look for key signs of bat habitation in a building, such as tile hanging, loose leadwork and flashings (particularly around chimneys), small cracks & openings and not to mention bat droppings.   However, if bats are found to use existing buildings, further survey work is required to detect their emergence and activity in and around a building.   These emergence surveys can only take place when bats are out of hibernation and flying around; between May – September only.

Certain species of bats also live in trees and the cutting down of a tree could be causing harm to a bats habitat or the bat itself.   Whilst arboricultural work is not directly policed in regard to bat protection, seeking ecological advice before removing a tree may be prudent and considerate.

The presence of bats within an existing building is by no means a show stopper to development.   With the right professional support of an ecologist the design can be taken forward coupled with appropriate mitigation, through the introduction of suitable bat habitation devices and details.   This information will be produced by the ecologist and submitted as a mitigation report with any planning application.   This mitigation report is also utilised to obtain a licence from Natural England enabling controlled works towards the completion of the proposed development with the protection of the bats in mind.

Early assessment will have significant benefits to a development project as it will enable the right ecology work to be carried out at the right time and it will allow the design to be taken in the right direction.   As architects we have a duty of care to advise our clients appropriately and to be aware of the basic principles in bat habitation potential.   With careful design and collaboration with a professional ecologist bat mitigation can be incorporated into beautiful design without being obvious.   The cladding on our Curvey Oak project has bat boxes and roosts designed into the elevation seamlessly … can you spot them?



What is a building contract and why do I need one?

For a traditional build, a building contract is the agreement your builders will work from to deliver your project within the cost and time frame you agreed, to the specification you expect.

The agreement is based on three main factors:

  1. TIME it will take to complete the works; The Date for Completion is agreed in writing with your chosen Building Contractors and entered into the Contract.
  2. COST of the Works; The Contract Sum as provided by the Contractor in writing and agreed by the Employer is entered into the Contract.
  3. QUALITY of the Works; Clauses within the building contract state that Works are to be completed in accordance with the Contract Documents. These are the technical drawings and specifications of the Works compiled by your Architect.

What role does your architect perform?

Your Architect will act as an independent administrator of the contract, known as the ‘Contract Administrator’, checking work onsite and ensuring the build is being completed in accordance with the three main factors (as defined within the Contract Documents) –

  1. TIME: If the Contractor thinks the build may take longer than stated within the Contract, your Architect will assess their claim for any Extensions of Time and whether their reasons are in accordance with the terms of the Contract. If they are not, you may be entitled to damages (as pre-agreed and written into the Contract).
  2. COST: Before payment to your contractor, your architect will inspect the works on site and certify they are being completed in accordance with the contract documents. This ensures you are never overpaying for Works completed at each stage of the build.
  3. QUALITY: This ensures that what has been designed is what is being built on site.

Forms of contract will be directly applicable to the size and type of your project. Your Architect will recommend the most suitable Contract for your build.

Are solid walls making a comeback?

House construction techniques have developed from historic solid wall methods.   Go back over 200 years and solid walls were made from local stone inner and outer faces with rubble, stone and earth between forming a dense and thick mass that held itself together.   Due to its thickness rain rarely penetrated the width of the wall.   Air tightness did not exist, in fact the walls were naturally breathable.   Thermal properties worked differently from today’s high insulation techniques aided by the thickness of the wall and the fact that the inner stone would have been warmed internally by open fires.

As bricks were developed in the 19th century the ability to build thinner walls, affording more internal floor area, became apparent.   Taller buildings used the method of thickening the masonry at lower levels and thinning out as floors rose.   Typically, a three storey brick built solid wall construction might see ground floor thicknesses at three bricks thick, first floor at two bricks and single skin for the top floor.   This method helped reduce weight as the building went up.

Thinner walls began to see rain penetrate to the inner face presenting all sorts of problems.   Thus, the cavity wall was born; using two separate skins of brickwork, the outer skin kept the rain out and being separated from the inner skin prevented transition of moisture to the inner skin.   Later, insulation was added to the cavity, an ideal place to locate and protect a soft product, to improve thermal performance.   So today, with relatively high performing insulation products, the understanding of how air tightness improves thermal performance* and other efficiencies in material fabrication, today’s cavity wall is a high performer.

So, why go back to solid wall, even with modern insulation products?   Where is the benefit over cavity wall techniques?

Wall thickness can be one benefit.   With insulation demand increasing, cavity walls are getting thicker, often over 300mm to meet today’s requirements.   A solid wall method, using single skin masonry (100mm), can be less than 300mm including rain screen cladding.   Placing the insulation on the outside enables the inner skin of masonry to act as a thermal mass, much like historic methods achieved, reducing the output of heating systems.   Thicker inner skins, perhaps using block laid flat (215mm), will improve thermal mass.

Remember, in a cavity wall, the outer skin of brickwork is not load bearing.   It is merely a rainscreen intended to keep the weather out.   Therefore, by replacing what is a relatively expensive product to buy and high labour intensity to build with something cheaper, sustainable and thinner whilst maintaining the inner masonry load bearing wall and, then outer insulation layer results in a modern solid wall construction.

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5 good reasons to employ an architect

Why would you employ an architect?
An architect is a building designer. They train for 7 years (as much as a doctor) to understand design within the built environment. They are skilled in many areas including; building design, planning policy, building regulations, building contracts and construction law to name a few. With such a high skill base why would you employ any other professional to design your building? Here are five very good reasons to employ an architect on your next building project:

1. Creativity. An architect sees opportunities that can improve your property both financially and through quality of space. They are problem solvers, trained to find solutions. Architects look at the bigger picture and design space specifically to your needs.

2. An architect can handle the paperwork on your behalf to save you having to negotiate the planning maze or try to understand the building regulations. They can also advise you on any other professionals you may need for your project.

3. Architects are trained professionals governed by a code of conduct. Every architect is registered with the ARB (architects registration board). Some are also members of the RIBA (Royal Institute of British Architects). Both organisations have a code of conduct for members to abide by. These codes are created to protect you as the customer and ensure you get the highest quality service from your architect.

4. Architects can support you while your project is being built. They can act on your behalf with great construction knowledge to ensure quality is being delivered by the builder too. They can provide routine valuation certificates (sometimes with the aid of a Quantity Surveyor) to ensure you are not over paying for the work completed on site.

5. An architect will consider the design quality of a space through a number of factors; how the space is intended to be used, site constraints, planning policy, best construction practice, what materials would be best to use and how to control costs.

Bizzy Blue Design Ltd is an RIBA Chartered Architects practice. It provides the highest level of design and architect’s services to its clients. Working primarily in the residential sector they also support commercial projects and historic & listed buildings. The personal one to one service brings a tailored service to each individual client maximising the potential of their project.

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What changes are in store for the April 2014 Part L Document?

HCD group – Changes to the Building Regulations Approved Document Part L

Scheduled for April 2014


What changes are in store for the revised Part L documents this April?

In an effort for the government to demonstrate a reduction in carbon emissions for the United Kingdom the new revision for Part L of the Building Regulations will be released in April 2014.   These changes are intended to make a step towards a potential zero carbon new build house in 2016 and extensions in 2020.   Generally speaking, the changes are targeting a reduction of 6% in CO2 emissions for new build houses and 9% in non-domestic buildings this time around.

This modest increase in thermal properties, rather than the projected more significant step, is a deliberate act by the government to easy the change on the economy.   Their figures suggest that these changes would result in a 1.2% construction cost increase.   Reality suggests that the increase is more likely to be significantly higher at around 8-10%, which will actually be quite a hit on the construction economy.


So what are the changes and how will they impact on design?

For new build houses all of the external fabric elements have had their U-values improved.   Typically, walls will be 0.18 W/m2K, floors & roofs will both be 0.13 W/m2K and windows/doors/rooflights 1.4 W/m2K.   Limiting standards, the lowest any element can be, remain the same as current levels.   One point is clear with the revised figures is that a specification will pass if within the typical U-value targets and the updated 2012 SAP (Standard Assessment Procedure) calculation system will also pass at these levels, which was not always the case.

The revised Part L bases its standard pass rate without the use of renewable energy though, allowing any introduction to be an improvement on the basic provision against carbon emission reduction.   Compensation against reduced U-values can be tackled with the introduction of renewables, for example.

Party walls have been reviewed after evidence was found to support the argument that they act like chimneys drawing warm air from the spaces out through the roof.   As a result U-values have been applied here too with an option to provide a solid wall with block laid flat construction, though this method is likely to require attention to combat noise transfer.   A full filled insulated cavity party wall is the best solution providing it is sealed at all exposed edges.

Fuel factors are a new element within the overall assessment.   This set of figures provides a pre-determined factor against which type of energy is being used within the building.   Gas is the preferred and best option while electricity gets hit the hardest.   Be careful when installing heat pumps that require grid electricity to run them.

Efficiency of installed equipment, such as fan system for heat exchangers in passive houses and all lighting units, have been improved.   This will have an impact on fan systems in particular with manufacturers needing to improve the efficiency of their products to avoid duct sizes increasing.

These principles are the same for extensions to existing dwellings, though the required U-values are not as low as new build.

Again, U-values to external elements have been improved for new non-domestic buildings but the most notable change is the reduction in air permeability.   This means that connection details and then the construction of those details needs to be carried out with more attention in order to achieve the requirements.   As with housing, renewable energy is not included in the basic specification level allowing these to be added as an improvement or as part of a compensation for reducing performance of other elements.

Both for domestic and non-domestic new builds a report has to be provided that demonstrates a consideration of high efficiency alternative systems, such as renewables, district heating or heat pumps perhaps.   A simple statement is required to explain why more efficient systems have not been employed but there is no method to enforce or challenge the report.

Extensions to non-domestic buildings have retained the current requirements for U-values.   However, renovation of existing thermal elements will now require consideration at building regulations and will have to meet the current standards.

In summary, there are general improvements to all external elements in terms of thermal efficiency that targets a reduction in CO2 emissions by 6% for domestic buildings and 9% for non-domestic and a new SAP calculation for domestic buildings; the 2012 system.   These all come as a stepping stone towards a projected ‘zero’ carbon level for both domestic and non-domestic by 2020.   Watch this space for the next set of changes in two years time, we might have only just got used to these changes by then.

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Why do we still build with masonry?

We are in the 21st century and still using a 200 year old technology to build our houses. Why?  With a number of alternatives available today we are going to ask why they are not used very widely.

In the UK bricks have been made and used in housing construction for decades. The clay used is a natural material that is easily extracted and processed to make bricks. Built as a cavity wall with insulation between we have now developed this technology to the Nth degree.

There are other technologies used in the construction industry; such as timber or steel frame, pre-fab systems and composite structures. Sometimes other constructions or objects are used to form spaces and houses like shipping containers. There are also products likeDurisol or Beco Wall Form that provide ‘lego’ style concrete filled wall construction.

So, why do we still use bricks (or masonry) and is there anything wrong with this technology? It’s a well known craft that has been passed down through generations. Where it has been developed into cavity walls and adding insulation it is quite a successful composite construction: it keeps the weather out, provides security. It’s a great method of construction that has been proven over decades.

Why aren’t other technologies used? Timber frame has been used to some extent in this country. However, it has suffered because of a combination of climate and poor weather protection or breathability. Steel framing has been used widely in industrial and commercial construction and probably becomes more efficient in larger buildings and multi-storey.

Technology has made major break throughs of recent years with the consideration of allowing composite construction and buildings as a whole to breath. This allows trapped moisture, a significant issue in the UKs climate, to escape without compromising the buildings integrity. Ironically, early masonry construction (circa 19th century) naturally allows the construction to breath. Sure, there was little insulation in a solid masonry wall between 450-600mm thick. But the combination of thick solid construction that water would find difficult to penetrate, lime mortar and plaster work with non-plasticised paint these construction methods were almost perfect.

There is a tradition of brickwork in this country. True the brick type does vary across the country. In some parts a vernacular stone is found and used extensively. The planning system often asks for in keeping appearances in building finish. These are all significant limitations.

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Vapour barrier or breather membrane?

Bizzy Blue Design Ltd has reviewed the various terminologies to understand the correct usage and application of this often misunderstood technology.

Understanding the different applications for these products could mean the difference between a high performance building and a damp one that would be very difficult to put right without starting again.   We have investigated their applications and understood their respective performance values to become better educated towards their specification.


  • Vapour Barrier (or Vapour Control); withstands vapour pressure and minimises gaseous vapour penetration
  • Breather Membrane; water resistant and vapour breathable


  • Vapour Barrier; applied internally to walls, roofs or exposed floors.
  • Breather Membrane; applied externally to exposed structures.

We understand that the principle of using a vapour barrier is to control and reduce the amount of gaseous water vapour within a building and prevent it travelling through an insulated external or exposed structure where risk of interstitial condensation may occur.   The vapour barrier is applied internally to minimise vapour penetration into the insulation layer.   A breather membrane is applied externally to act as a barrier to water from the outside whilst also allowing the structure behind to breathe away any water vapour within it.   Using both products together as part of a composite structure will act to minimise water vapour penetration from inside the building and through the insulated structure, while allowing any vapour to escape externally and resist water penetration from the outside.

A traditional masonry cavity wall would not require a breather membrane as the external skin would act as the breathable layer and would control the level of water penetration from the outside.   A breather membrane would, however, be applied to a timber framed external wall that then has a masonry outer skin as this would protect the timber from any water within the cavity.

This theory works perfectly and logically on any external element (wall, roof or exposed floor) in contact with external air.   However, exposed floors, such as a ground floor where there are no basements, need to be treated in a different manner.   Where the ground is the external substance you are dealing with ground water pressure and this should be resisted by a Damp Proof Membrane or water proof tanking system.   Depending on where the floor insulation is positioned, a breather membrane can then be applied over the insulation to allow any water vapour or moisture to evaporate into the heated space above.

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