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Attic Conversions- What You Really Need to Know

This has always been seen as a straightforward way to add more space cheaply; but historically, attic conversions in Ireland have had enormous shortcomings in terms of structure, energy efficiency, usability and compliance with fire safety rules. There is a surprising amount to know before undertaking an attic conversion, and it’s important to proceed carefully because there’s a lot that can go wrong, sometimes leading to expensive mistakes.

It is crucial to start the process paying due respect to the challenge of turning an ancillary structural void which was never intended to be occupied, into a fully certified, high quality living space. The attic of a pitched roof house includes critical parts of the various systems that make your house function: the roof timbers control how loads are spread to the walls, insulation is part of a continuous thermal blanket, ventilation pathways and air tightness barriers are critical parts of the technical design, basic waterproofing is an obvious concern, and attics are also locations for elements of the plumbing and electrical systems, which are becoming ever more complex in response to climate change. When undertaking an attic conversion, it’s tempting just to create an adhoc structure under the old rafters and put in a roof-light, and many cheaper conversions do just this: destroying critical elements of the building without creating working replacements.

As you can imagine, it is very cheap and easy to do an attic conversion badly, in fact, you have probably seen attic conversions which included few of these considerations. The culture of compliance and standard of technology in the Irish property industry has changed radically in the last decade and you need to be sure any work to your home will pass inspection by a structural surveyor in the event that you sell or remortgage the house; or if it is assessed for insurance purposes, perhaps in the event of storm damage.

The main checks for the design of an attic conversion are:

  1. Ensuring a primary fire escape route through the house, with a fire- protected hall, stairs and landing leading to the front door, from the attic room door. 
  2. All doors in the house may need to be upgraded, and the fire detection system may also need to be replaced throughout the house. 
  3. Ensuring a secondary fire escape route through a properly designed fire escape window in the new attic room.
  4. Locating a Part K (building regs) compliant stairs within the layout of the floor below.
  5. Ensuring ventilation, head height and ceiling height. 
  6. Ensuring correct installation of insulation and an overall thermal/ air-tightness strategy- usually meaning pitched roofs need to be completely stripped, fitted with several layers of insulation and re- tiled/ slated.
  7. Floor structures should be of correct thickness and design. 
  8. Structural design should transfer loads to ground via proper structural elements, often requiring a prefabricated steel frame at attic floor level, and sometimes even steel columns down to foundation level.
  9. Specialist roof finishes are often required, particularly for low pitch areas, and complex junctions. 
  10. Water storage tanks typically need to be relocated, but changes to plumbing systems may include elements of solar water heating systems, photo voltaic systems, or even old-fashioned gas boilers.  

Value Adding Design- A Surprising Opportunity for Luxury

That said, attics can be rich and complex spaces, and can hold great appeal as unexpected architectural experiences hidden at the tops of ordinary homes. We have designed many intriguing attic spaces over the years. When carefully designed they can add hugely to the overall quality of a home.

Attic conversions, or top floor extensions, can be particularly important on small sites, where garden space is at a premium.

One of the main motivations for using these spaces is the potential to exploit complex leftover spaces at the ridges and eaves of the roof space. This can best be achieved by designing bespoke furniture and fittings to fit everyday functions into the available three dimensional volumes.

Two Main Approaches 

Attic conversions to standard speculatively built houses can be divided into two groups: those which stay within the existing roof shape, and those which require the roof shape to be changed. 

Conversions Entirely within Existing Roof Profile

  1. Don’t usually create habitable space, in terms of the building regulations or planning
  2. Planning exempt if new windows more than 11m from the boundary they face
  3. Can generally comply with requirements for fire safety
  4. Cannot generally comply with requirements for head height, and as such will always be classed as storage space, or other non habitable space, even if planning is sought and approved. 
  5. Can comply with all applicable building regulations in some rare and exceptional circumstances, when the internal space in the attic is more than 3 meters at the highest point. 
  6. The construction prices for these projects historically range from €25,000- €30,000. 

Conversions With Changes to Roof Profile

  1. Must be “considered top floor house extensions”, rather than attic conversions, from a budget perspective, and in terms of planning permission status.
  2. The client’s goal is usually to create a large “flat roof” area with full ceiling height, concealed behind existing or new flat roof facets, in keeping with the existing architectural style of the neighbourhood.
  3. Contemporary “box on top” designs often use sheet metal to contrast with the preexisting roof, and historically “mansarde” roofs and some dormer designs were conceived in this way.  
  4. Construction cost is estimated based on the same standard cost per square meter for new construction used for house extensions in general, as they are far more complex than conversions within the envelope of an existing roof. 
  5. Can usually create habitable space with full ceiling height if the bottom of the ridge board of the house is more than 2.5m from top of ceiling joists of the story below, and if a flat roof area can be approved for planning permission/ exemption. 
  6. All building regulations can usually be met on such projects.
  7. Changes to the roof shape will be subject to planning permission, except in some very exceptional circumstances where they can be built as exempt house extensions. This is effectively only possible when adding relatively small floor area to larger detached houses.  
  8. Planning permission would be fairly difficult to secure unless there is an established precedent for visually similar developments in the same planning context (nearby area).

Professional Fees

Professional fees for an attic conversion are generally disproportionately high, relative to the low cost of construction. But this does depend on the route chosen for procuring the work. If structural design is finalised onsite, with the contractor taking responsibility for structural certification it allows for a much more flexible and cost effective approach. Otherwise everything must be measured and drawn in exhaustive detail.

This greatly reduces the scope of drawing work, but it can only be attempted when dealing with a trusted building company, usually working in tandem with a structural engineer.  

Latent Defects are Rife in Historic Attic Conversions

It is important to say the overwhelming majority of attic conversions from before 2015 have very significant latent defects. They often look fine, at first glance but are unable to withstand possible storms or snowfalls, are impossible to heat, or have even damaged the structure of the house below. This is because attic conversions are actually complex design and construction challenges, which can either be achieved by a specialist contractor with a lot of experience and a “tried and tested formula”, or by using a full design team to ensure everything is planned and executed correctly.  

Budget attic conversions, DIY attempts, and work by unscrupulous contractors are to be avoided at all costs. The following rules of thumb may help in selecting a competent builder at the right price:

  • In the last ten years, we have not encountered any attic conversion which achieved full building regulation compliance for a contract price of less then €23,000. This price was for a conversion entirely within the original roof envelope.
  • A 25m2 top floor bedroom extension, creating a large master bedroom suite with bathroom and dressing room, and including complete replacement of the roof with a new dormer structure “should” cost in the region of €80,000- €100,000 based on current standard rates.
  • Your contractor may offer to design the structure; this may be a very good approach, but they will need to provide details of a qualified engineer who can certify their work.
  • “Attic conversion specialists” may meet these criteria, but be ware of companies targeting this form of construction, and check their references, insurances and qualifications.
  • Attic conversions are also potentially profitable for unscrupulous contractors, because the defects are not obvious to the untrained eye. Costs can be slashed if you omit critical features like additional fire doors, steel frames, additional fire linings, cold bridge insulation to the outside of the roof, and scaffolding the outside of the building, all of which are now usually necessary to achieve compliance.
  • Ask a contractor’s previous customers to describe their experience of the process, or get your architect or structural surveyor to visit one of their previous projects.

Required Architectural Services

In addition to the core services required for any architectural project, the key professional services for attic conversions are: 

  • Locating the existing structure with an exhaustive survey of the existing house, from foundation to roof ridge, (every wall and roof timber must be measured precisely.)
  • Accurately modelling  the space
  • Creating a three dimensional design for  the resulting attic spaces
  • Securing planning permission against legitimate concerns regarding the visual impact and overlooking impact of such developments. 
  • Creating accurate drawings to share with a structural engineer
  • Inspecting the fine detail of the work during construction, including a lot of steps in which errors can be concealed easily.  

These are in fact complex and onerous projects from our point of view, as reflected in our legal responsibilities and our fees. The architectural fees are almost identical to those for a high quality ground floor extension of equivalent floor area, subject to planning permission.  

Structural Design Options

It is possible to either appoint an engineer to design changes to the structure, working from architects drawings, or to employ a contractor with structural design included in their service.

The difference is: one will be a paper- based approach, where the design will be figured out in advance and defined in drawings and contracts; the other will allow for figuring out onsite, which is faster and more intuitive, but which leaves a lot more scope for the price to vary during construction. 

Note, whatever happens, if you want to sell a house with a converted attic, you will need at least an engineers’ certificate stating that the works comply with Part A of the building regulations, and an architect’s opinion on compliance that the works are not unauthorized development from a planning perspective. There needs to be a clear understanding of how this will be organised if the main contractor is responsible for structural design. It will be extremely difficult to obtain certificates retrospectively.

A conscientious and well informed solicitor acting for you (or your bank) may require additional certificates up to an architect’s opinion on compliance with building regulations. 

Certification and Quality Control- What About Just Accepting the Risk of a Cheaper Option?

A lot of people deliberately opt to create a conversion which cannot be certified within the building regulations in the knowledge that it would only become an issue if the house were to be sold. This is a reasonable position if they are merely looking for cheap storage space. However, even if the space isn’t classed as habitable, on paper, the building work must still comply with the building regulations. There are serious “real-life” consequences to the kinds of defects which are common in poor quality attic conversions:

  • Excessive air infiltration, increasing household heating costs dramatically
  • Intermittent  or patchy insulation installation creating condensation problems, mold and staining
  • Fundamental problems with the structural redesign of the roof, making the roof susceptible to collapse under “once in a century” wind or snow load. 
  • Placing structural loads on internal partition walls, causing plaster cracking, structural cracking and problems like deformation of internal door frames.
  • Party wall liability issues where shared structures are modified as part of the works without appropriate authorization or design.
  • Inability to escape from the attic roof in the event of a fire.
  • Damage to the smoke compartmentalization structures of the floor below.
  • Damage to the smoke and fire separation elements separating your home from adjoining homes.  

It is hard to assess the viability of an attic conversion without getting in and physically measuring it. We recommend contacting us, or another qualified architect with experience of domestic renovations for a consultation onsite.

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