Property

Builder says our attic conversion should be classed ‘non-habitable’. Is this right?

To classify the space as a store when it is to be habitable can pose a real risk to occupants

As always, there is a loophole that is typically exploited. Photograph: iStock

Tue Oct 1 2019 - 06:00

Due to our expanding family, we need to extend our home. Based on quotes from builders we have decided that an attic conversion is the most cost-effective solution. A lot of our neighbours have already converted their attics achieving a good-sized bedroom and en suite. However, our builder says the space must be classed as “non-habitable” to avoid a lot of additional work to the main house. I’m a bit confused by this as the space is to be used as a bedroom for our two daughters. Can you cast some light on this issue?

With clever design the conversion of an attic can deliver good-quality additional space and be cost-effective. It also avoids loss of valuable and sometimes limited garden space. A number of important issues arise, however.

The first relates to the roof structure. Most modern speculatively built houses delivered in the past 50 years are constructed using prefabricated timber roof trusses. These are triangular and are formed enclosing W-shaped supports and hangers. The triangular outer frame provides the common rafters that support the roof tiles and the bottom section forms the ceiling members of the roof structure. These are extremely efficient structural elements and they work on the basis of transferring roof self-weight, and loads imposed on the roof by wind and snow, to the load-bearing external walls without placing any load on the internal non-load-bearing lightweight partitions.

The timbers used in truss manufacture are more slender and are placed farther apart than traditional cut timber roof members. The conversion of an attic, where the roof is formed with a truss, means that this preformed structural element needs to be altered or cut and partly removed. The roof essentially becomes a cut roof meaning the transfer of weight is handled differently.

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I have seen cases where the weight from the roof, attic floor and heavy water tanks has been incorrectly transferred to the internal partitions. In such cases settlement of the roof and attic floor structure ultimately takes place and remedial works are difficult and costly to execute.

The issue of structural design and liability arises. The original roof truss will have been designed by a structural engineer and its alteration and replacement by new structural members should also be designed and certified by an engineer. This aspect is often overlooked, and I’ve seen this lead to delays where these properties are offered for sale later. Certificates of structural adequacy and compliance with the building regulations (Part A) are typically requested during due diligence. It can be difficult to obtain these in retrospect as important elements will be covered up.

Secondly and more critically, the requirements of building regulations with regard to fire (Part B) are different for a house with a third storey as there is perceived to be greater fire risk. The extra risk introduced by an additional storey is mitigated in the regulations by the requirement to provide self-closing fire doors to rooms and closets where these lead on to the staircase. It is also a requirement to provide fireproof partitions to the staircase enclosure and to provide fireproof floors throughout the house. Structural steel supporting the new attic floor should be encased in fireproofing.

These are passive measures that improve the time available to escape from the house in the event of a fire and facilitate entry by the fire brigade. A high-quality, mains-operated smoke detection and alarm system is also required. These safety measures are required because the upper-storey windows are too high above the ground to allow search-and-rescue personnel to assist in the safe evacuation of occupants should the staircase become impassable due to smoke or fire.

Therefore, where the conversion of an attic is required for habitable space, then the rest of the house would also need to be upgraded if the completed house is to comply with building regulations. This comes at a cost and this can push the viability of the conversion beyond what would be considered value for money.

As always, there is a loophole that is typically exploited. Some feel that by not classing the space as “habitable” and by merely calling the converted attic a “store”, then the rules do not apply. While this may be factually correct, it is at some level fooling yourself, particularly if it is intended to use the space for habitable purposes.

I can understand the need to provide additional space in homes by the most cost-effective means available. However, in my experience these conversions are typically used as habitable space and commonly as a child’s bedroom. To classify the space as a store while in reality the space is to be habitable can pose a real risk to occupants.

The use of the room determines what safety measures need to be put in place. The building regulations are concerned with safety and the requirement to upgrade fire precautions with attic conversions is concerned primarily with means of escape. I like to compare the passive safety measures mentioned above to safety barriers along a narrow mountain road. These are “waiting to work” if needed. The absence of the barrier, if called upon, will lead to a rapid plummet into the ravine.

There is a good information leaflet published by the Department of Housing available online. Just search for “Department of Environment attic conversions”.

If the required fire precaution measures are not put in place, then clearly life safety is being compromised.

Have a chartered building surveyor assess the house and help guide you on the minimum requirements needed to meet the current regulations before you decide to start works. A fully compliant conversion and the classing of the accommodation as “habitable” will add real value to your property. The addition of a “store”, not so much.

Using a loophole to save money when there is a potential cost of life is risky.

Noel Larkin is a chartered building surveyor and member of the Society of Chartered Surveyors Ireland, scsi.ie

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