In plain sight: a tweak to planning rules could unlock up to 350,000 small homes

Executive Summary

• Planning policy already allows homeowners to build structures in their gardens without planning permission, but they are not currently allowed to build a small home in their garden.
• We believe these rules should change. We should let people build small homes in their gardens.
• Progress Ireland’s modelling suggests that a seomraí (or ‘granny flat’) policy could deliver up to 350,000 new homes.
• Ireland can learn from successful ‘accessory dwelling unit’ (ADU) policies around the world.
• Progress Ireland has eight recommendations to make seomraí a success.

Closing the housing gap with seomraí

It is hard to comprehend how many homes Ireland needs to build. The Housing Commission reported that in 2022 Ireland’s housing deficit was over 200,000.¹ That’s what we need just to catch up with existing demand. In addition, the commission estimated that Ireland needs to build 60,000 homes per year, every year, to meet growing demand. That means we have to build a new Galway city every six months. Or a new Dublin city every four years. 

Filling the gap is a difficult task. There are significant constraints, made more difficult by where the homes need to go. To reverse environmentally damaging sprawl and to create sustainable communities, the government set out its compact growth targets. These targets earmark 40 per cent of new development to existing settlements. We know that delivering compact growth has to be part of the solution to Ireland’s housing shortage. The difficult part is how to deliver new homes at scale within existing urban and suburban areas.

Building the homes we need will be hard for at least two reasons: land and cost. 

First, land. Irish cities simply do not have enough brownfield land on which to build 24,000 homes per year.² And it looks like there will soon be a shortage of zoned and serviced land for housing delivery in the eastern and midlands region.

Second, cost. It’s expensive to build small homes. Dublin is the second most expensive city in Europe to build an apartment. Apartments can’t be built in urban areas for less than €379,000 to €479,000. The cost of delivering apartments rose by 9.6 per cent in 2022. 

We call our solution to these problems seomraí.³A seomra is a small secondary dwelling built either behind or to the side of an existing property. Such dwellings typically have a separate entrance to the primary dwelling on the plot. They may be attached or detached. Their use may be as a form of private rental accommodation or for the use of a family member or friend. 

Seomraí sidestep the land problem. While our towns and cities do not have an abundance of serviced available empty sites, what they do have is an abundance of serviced privately owned residential land in the form of gardens. There are 3,305 hectares of private garden space in Dublin city council’s area.⁴ That is about 300 St Stephen’s Greens. 

Seomraí also overcome the cost problem. Where an apartment can cost over €400,000 to construct in Dublin, a seomra can be delivered for around €70,000.⁵ The simplicity of seomraí design allows them to keep costs down.

Low construction costs are not just a matter for developers, rising construction costs ultimately mean higher rents. The simplest way to ensure affordable homes is to design the property with affordability in mind. Due to their scale and simplicity, seomraí are affordable by design, without sacrificing quality. 

Seomraí are proven. They are an integral part of healthy housing systems in other countries. In Vancouver, 35 per cent of all single-family homes have some form of seomraí.⁶ In California, 11.5 per cent of all permitted homes were accessory dwelling units (ADU) – a form of seaomraí – in 2020. 

Unlocking seomraí at scale is achievable. Several jurisdictions have succeeded by removing some of the legal and regulatory barriers to building seomraí. For instance, by removing some barriers such as owner-occupancy requirements, Seattle increased ADU permits by 253 per cent in just three years. In six years, California’s ADU approvals went up by 15,334 per cent. As of 2022, 19 per cent of all housing units produced in California – or nearly one in five homes – was an ADU.

Seomraí are a popular policy choice around the world. Other countries are beginning to recognise the potential impact of seomraí on housing supply, sustainable development, and accommodating demographic change. Accelerating granny flat development is a national policy priority in New Zealand. In Switzerland, they are considered an investment opportunity for retirement. This year, the French Senate proposed a bill to allow more development in private gardens. In Australia, there is a growing appreciation of the potential of granny flats. The New South Wales government encourages them; in Victoria, they do not require a planning permit; and in Western Australia, they are exempted from the planning approval process altogether. 

Seomraí have worked elsewhere and they would work in Ireland.

Seomraí could deliver up to 350,000 homes

How many gardens are suitable? To answer this question, we built a model. We randomly sampled 200 properties from a list of all registered eircodes in the country.⁷

The first thing we checked for was space. How many gardens had enough physical space to fit a seomra and ensure access?

We assumed the minimum size of the seomra itself was 25 square metres. We further assumed one-metre gap between the seomra and the boundary wall. The minimum remaining garden space (after the seomra was built) in our model was 37.5 square metres.

Our size assumptions are conservative. We err on the side of underestimating the number of properties that meet our size criteria. Separation distances rules are subject to the time it would take for a fire to spread; the minimum acceptable distance can be brought below one metre using fire-resistant materials. Therefore our model will understate the number of seomraí that will be within separation rules.

We considered a property accessible if it met two criteria. First, the property was accessible if it had a side passage no smaller than one metre. This size is greater than the minimum required for disability access. 800 millimetres, ie 0.8 metres, is sufficient to allow access for construction crews and their equipment to access the garden. Here again, we chose to be conservative in our estimates to allow for measurement errors. Second, the property was accessible if it was within 45 metres of a vehicle access point. This distance is required by law to enable fire services to access the property. 

56 per cent of our sample had enough space – access, boundary, remaining garden space – for a 25 square metre seomra. Apartments were excluded from both the sample and the population.

The next test was financial: are the all-in costs of a seomra (construction costs, finance cost and a 15 per cent margin) greater than the value a seomra would be expected to add to the value of the house?

To estimate what a seomra would add to the value of a property, we used two numbers: the estimate of local rents, and the market’s gross yield (the rate at which rents convert into home prices).

We derived our estimate of the rent from Daft.ie data. We took the average market rent for one-bed apartments in the county, then discounted it by 15 per cent to account for the smaller size of a seomra.

To convert the rent into the capital value of the home, we assumed a gross yield of 13 per cent. Choosing a yield inevitably involves guess work, since it’s our estimate of the market’s estimate of a category of home that doesn’t exist yet. We started with the market’s average yield for one beds, which is currently 7.2 per cent in Dublin City and 9.5 per cent in Cork city. We then discounted the market’s yield to account for the illiquidity of seomraí. All things being equal seomraí should be worth less because they can’t be sold individually, like a normal apartment. The gross yield we landed on was 13 per cent.⁸

Why the big discount on the market’s prevailing yields on one beds? Adding a seomra would undoubtedly add complexity for the homeowner. They would become landlords, with all the obligations that implies. An important detail is that there might be a difficulty selling or remortgaging the property if a tenancy is still ongoing. A homeowner would be better entering into a lease if they were confident they wouldn’t be selling or remortgaging during the period of the agreement.

Our estimate of how many homes are suitable for seomraí is calculated as the proportion of homes that meet space, access, and financial criteria. 20 per cent of homes in our sample met these three requirements. This scales to 348,730 homes across Ireland.

The model we have built is interactive. (To interact with the model’s inputs, click here, then make a copy of the sheet under the File menu in Google Sheets.)

Seomraí play an important role in housing systems around the world 

Seomraí have proven successful across several countries. Four important questions about the international experience are: Have they achieved scale? How was this achieved? Are they popular? Are they affordable?

The potential of seomraí to deliver homes at scale is not fully recognised in Ireland. Though seomraí seem like a small idea, they can achieve a lasting impact.

What are called seomraí here are called ‘accessory dwelling units’ or ADUs in the United States. In Canada, when detached, they are called laneway homes; when attached, they are called secondary suites.  

In the United States, the proportion of rental listings that were ADUs increased to 6.8 per cent of total listings between 2003 and 2019.⁹ Across the state of California, they made up over 11.5 per cent of total units permitted in 2020. In 2022, 1 in 3 homes permitted in Los Angeles was an ADU. At least 26,862 ADUs have been permitted in LA alone since legalisation.¹⁰

The thing that changed was regulation. Before 2016, regulations set by the city of Los Angeles prevented many ADUs from being built.

ADUs have experienced growth beyond California. Portland, Oregon has been a world leader in ADUs for decades, building more ADUs per capita than Los Angeles. Seattle achieved a 253 per cent increase in ADU permitting between 2019 and 2022. By 2022, ADU construction overtook single-family home construction. Approximately 35 per cent of single family homes in Vancouver either have a laneway home or secondary suite, both forms of ADU. They make up about a quarter of all rental units in Canadian urban areas. 

ADUs have produced homes at scale in California, Portland, Seattle, and Canada, as we have seen. How was this achieved? 

There is no simple answer. But there are some commonalities. Each jurisdiction achieved scale on the back of removing regulations which inhibited supply. In each case, the expressed purpose of the change of policy was to boost the supply of ADUs. In none of the examples was scale achieved by accident. Progress Ireland’s proposed regulations in section five are designed to encourage seomraí production here in Ireland, taking the lessons of international experience into account.

First, California. The scale of ADU development achieved in California did not happen quickly. While ADUs have been a common typology since the 1980s in California, their presence increased rapidly after 2016. Many mistakes were made in the intervening years that limited supply, including allowing for cross county variation in regulations, high levels of discretion in the approval process, and owner-occupancy requirements. When the regulations were gotten right, ADUs rapidly achieved scale.

Between the years of 2016 and 2022, ADU permits increased by 15,334 per cent. In 2022, nearly 25,000 ADUs were permitted in California. In 2023, total ADU permits rose to 27,969.

Similar scales were achieved in Seattle, Washington. The scale of ADU production in Seattle was achieved by adopting regulations explicitly designed to encourage supply.

Several regulatory barriers were removed in 2019, such as minimum parking and owner-occupancy requirements. In 2020 ADU permits increased by 75 per cent, despite the impact of the pandemic. Relative to the 2011 figures, ADU permits were up by 819 per cent by 2023. 

Portland had already avoided a lot of the early mistakes of California and Seattle but prior to 2010, the supply of ADUs was still limited. 

In 2010 a steep development levy to the city called a system development fee was suspended. Designed to cover servicing costs, this fee was as high as $7,000 to $12,000 per unit. These fees were suspended again in 2012 and again in 2016. In 2018, the fees were permanently scrapped with the proviso that all ADU’s exempt from the system development fee not be used for short-term rental accommodation for the next 10 years. 

ADUs permits increased by 2,228 per cent between 2009 and 2018, when ADU permits peaked.

Charges such as the systems develop fee inhibit supply. The suspension of the System Development Fee bears a lot of resemblance to the recent Temporary Development Contribution Waiver. In both cases, the fee being waived unfairly favours incumbents over newcomers. And in both cases, removing the fee has stimulated supply. 

Vancouver has been incrementally increasing the scale of ADU construction arguably since the 19th century. Secondary suites were banned during the 1950s, in a move parallel to Ireland’s banning of bedsits. But they were brought back in the 1980s. Inspection fees were reduced in 1989. By the 1990s, it was estimated that 23 to 27 per cent of homes in the city had a suite. In 2004, the city council allowed for secondary suites in all residential zones. Between 2004 and 2006, various restrictions were eased but not totally eliminated. Laneway homes were permitted in single family zones in 2009. Since 2017, Laneway homes represent nearly half of the permits issued by the city in residentially zoned lots.

As we have seen, seomraí have delivered homes at scale. But are they popular?

ADU policies seem to compound over time, as we have seen. They start slow and grow in their ambition. This is a powerful sign that political leaders do not regard regard ADU policies as unpopular. The spread of ADU policies continues in the United States. In June of this year, Massachusetts passed an ambitious ADU policy.

One reason for this popularity is that they present a win-win for renters and homeowners alike. Where seomraí are widely available, renters have more options for affordable homes. Where the regulations make building a seomra easy, homeowners have an effective means to earn extra income and increase their property value. That’s why in Vancouver, they are sometimes referred to as ‘mortgage helpers.’

The scale achieved by successful seomraí policies around the world is indicative of the popularity of small homes. It is encouraging that pro-ADU policies in the United States have tended to compound rather than regress, suggesting that there is not significant push back from local residents.

The popularity of seomraí has been tested at the ballot box. In Vancouver, the 1988 municipal elections included a referendum asking voters whether they wanted secondary suites to be permitted in their neighbourhoods. 

The referendum was a massive success. 47 per cent of neighbourhoods opted into the new zoning provisions allowing for secondary suites (a form of attached ADU). The implementation period that followed enabled Vancouver to become the world’s leading city for ADUs. 

According to senior planners in Vancouver, the laneway house program has been “incredibly successful.” Demand is so high in Vancouver that the city’s permitting system is “considerably backlogged.”

Seomraí are popular among both the young and the old. In New Zealand, the government’s granny flat policy is designed with these two groups in mind.

A US survey of 12,000 people across 26 major cities found that 84 per cent of renters aged 18-42 support “missing middle” housing, which includes ADUs.

Seomraí are a popular way to enable ageing in place. One of the most influential supporters of pro-ADU policy in the US is the American Association of Retired Persons (AARP). A 2018 survey conducted by the AARP found that 67 per cent of American adults would consider living in an ADU to ‘age in place’. A more recent AARP survey found that 60 per cent of adults polled said that they would consider living in an ADU. The majority of those in that cohort – 69 per cent – said their primary motivation for living in an ADU was to be close to family and community. 

According to Danielle Arigoni, the director of the AARP’s Livable Communities program, retired people don’t see many tenable housing solutions around. But “ADUs are a really elegant solution to diversifying the choices that people have in housing,” she said. 

A major reason for the popularity of seomraí as a typology is their affordability. Seomraí tend to be affordable relative to market rents. Rental prices for seomraí differ significantly across jurisdictions. Given their comparatively low construction costs, seomraí build-in affordability.  

Rents for ADUs vary significantly across jurisdictions, as do their size. In many areas, ADUs are found in areas with below median household income. 

A report on ADU financing from UC Berkeley found that 20 per cent of ADUs built between 2016 and 2019 were built in areas with household incomes of less than 85.5 per cent of the median household income. 

In a survey taken in Oakland, California the city reported that the average rent of an ADU was affordable for those earning just 60 per cent of the city’s median income. Across California, the median rent for granny flats is considered affordable by the state, meaning they go for less than 30 per cent of the local median income of a couple. 

A UC Berkeley survey found that 58 per cent of respondent ADU owners rent them for below market rents.¹¹ The Southern California Association of Governments released a report breaking down the affordability of ADUs across different counties. A rent is affordable, in the report, if it is less than 30 per cent of the household’s net income. In LA county, low-income households would benefit the most with 51 per cent of ADUs affordable to that income bracket.¹²10 per cent were available for those in the very low-income bracket.¹³ Some ADUs were found to be available for those making less than 80 per cent of the area’s median income.

By removing land costs and reducing overall construction costs, it is little surprise that ADUs are typically affordable in the US.

The case for Seomraí in Ireland

The first benefit of Seomraí is that they enable rightsizing. Ireland needs a rightsizing strategy. The Department for Housing, Local Government, and Heritage estimates that 150,000 rightsizing homes will be required by 2031. They define rightsizing homes as “smaller dwellings designed to meet the needs of older people.” Seomraí could unlock thousands of homes that enable rightsizing.

A survey of 554 adults aged 55 and over by the Housing Agency and Ireland’s Smart Ageing Exchange showed that the majority of older people cared more about staying in their area rather than their particular dwelling. A strong seomraí policy would allow older people to rightsize, without leaving the communities that they call home. That is one of the reasons why the Royal Institute of the Architects (RIAI) and the Association of Occupational Therapists of Ireland (AOTI) support “the provision of accommodation that reflects the identified demographic and support needs of the population of Ireland and acknowledges the right of people to choose to remain in place.” The provision, they note, should include both attached and detached granny flats.

According to the CSO, the population of over sixty-fives is projected to increase by 700,000 to 1.5 million by 2050. To accommodate this change, we will need more small homes. This is a point recognised by the Department of Housing, Local Government, and Heritage. Meeting the challenge of an ageing population head-on means creating more housing options for every stage of life. Seomraí are one tool among many to meet this challenge. 

The second benefit of Seomraí is the "cascade effect" – the extra housing that is unlocked when people downsize into a smaller home.

Part of Ireland's housing problem is a shortage of housing. Another part of the problem is a mismatch between the houses we have and the people living in them. We have lots of family homes crammed with renters.

Seomraí will help match small households with small homes. In doing so, they'll free up family homes for everyone else.

There is pent up demand for small homes in Ireland. Household sizes are tending toward the EU average of 2.3. The average household size in Ireland is 2.74, down from 3.34 in 1991. As a result, there are too few small homes, for one to two people, on the market.

Seomraí will help connect people’s preferred household size with the types of housing available. This will free up larger family homes. Homes more appropriate for families are misallocated to two groups: older people seeking to rightsize, as discussed, and younger crammers.

A third benefit of seomraí is that they help homeowners pay the bills. In Vancouver, renting out an ADU is so common partly because it helps ease the burden of a mortgage. They call them ‘mortgage helpers.’ Enabling homeowners to meet the growing cost of living while providing a home to the market is a win-win. 

A fourth benefit of seomraí is that they can help cut carbon emissions. Seomraí are one tool among many to help curb our carbon emissions. Areas with higher densities are the most environmentally friendly. A strong seomraí policy would allow an increase in the supply of homes in the areas with the highest demand. Restrictions on building in the areas with the highest demand leads to dispersed development and higher emissions. 

That is why the Climate Action Plan 2024 is informing the revision of compact growth goals in the National Planning Framework. Seomraí are one powerful means to achieve compact growth, helping Ireland deliver homes where they are needed most.

Seomraí could be fitted with a ‘green roof’, contributing to biodiversity. Typical suburban gardens usually contain monocultural grass. Unused sheds or underused structures such as gyms could be replaced with a home which contributes to biodiversity in the area by its green design.   

A fifth benefit of seomraí is that their benefits are targeted at groups who are feeling the housing shortage most acutely. Seomraí could provide additional housing options for students and young professionals currently priced out of the market and low down on housing lists. Young people are staying in the family home far longer than they would like. Between 2011 and 2022, the number of adults living with their parents rose by 19 per cent. That’s a change of 83,008. Irish people between the ages of 25 and 34 are over 3 times more likely to live with their parents than Germans of the same age. Seomraí could help our young people get their start by providing affordable accommodation.

A sixth benefit of seomraí is that they can help accommodate carers. A seomraí policy could enable the implementation of the National Housing Strategy for Disabled People 2022-2027. That strategy highlights the goal that people with disabilities should be enabled to live independently. According to a 2018 study, 84 per cent of families with a disabled relative in the United States would consider building an ADU. A RIAI and AOTI report sketches out how detached or attached granny flats could be used to enable people with disabilities to live independently here in Ireland.  

Affordable housing for carers is increasingly necessary as the population ages. Seomraí can provide cost-effective living spaces for carers, supporting the essential role they play in our society.

Recommendations to make seomraí a success

Recommendation one: The minister should encourage the development of Seomraí through the planning system.

At present, current development plans do not make provision for seomraí. In fact, the typology is highly restricted.¹⁴ Sections in each development plan relating to detached habitable rooms and ancillary family accommodation should be revised. These plans make seomraí very difficult to build by restricting the use of ‘detached habitable rooms’ for accommodation and placing stringent requirements on ‘ancillary family accommodation’. 

Using the new ‘national planning statement’ (NPS) instrument, the Minister could set out a comprehensive seomraí policy enabling the construction of small homes across the country. This would enable the minister to enact and shape seomraí policy across all tiers of the planning system. 

Design and size standards should be at the heart of the national seomraí policy. These standards should be at once sensitive to considerations of supply and neighbouring amenity. Recommendation 6 below sets out Progress Ireland’s proposed standards. 

Recommendation 2: The minister should make seomraí a form of exempted development under the Planning and Development Act.

Changing development plans is unlikely to be sufficient in making a seomraí policy successful. The international case studies show that permitting seomraí in a highly limited range of cases stymies supply. What works is reducing friction as much as possible. Allowing seomraí to receive planning permission in a restricted range of cases at the discretion of a planning authority resulted in low levels of supply across several countries. It is therefore imperative that we do not repeat the same mistake. 

Obtaining standard planning permission is a slow and uncertain prospect. International experts on seomraí suggest that using a discretionary system for permitting seomraí restricts supply. Following the example of New Zealand and Western Australia, we should make it as easy as possible to build seomraí. International examples suggest that introducing uncertainty into the process will deter seomraí from being built. 

Section 9 of the Planning Bill covers the category of exempted development. A development is exempted if it does not require planning permission. For instance, extensions to the family home that are contiguous with the main house are exempt up to 40sq.m.

Local authority planning departments are understaffed and overstretched. Placing seomraí in the exempted development category would create a pipeline of homes that does not cause delays in larger development applications due to understaffing.

Due to the size and scale of seomraí, we believe they can be appropriately placed in the exempted development category. Including seomraí in this category will not extend or increase the scale of exempted development already permitted.

Exempted regulations – covering matters such as the height of the structure – should not change. This means that, from the point of view of neighbours, there will be no change in the scale of what is permitted in neighbouring gardens.

While we recommend seomraí be exempt from planning, we believe a seomraí policy should be uncompromising on quality. Our next recommendation addresses quality enforcement.

Recommendation 3: Building standards should be upheld for seomraí using the existing system of certificates of compliance. Minor amendment to the Building Control regulations should be made to preclude an opt out of statutory certification for seomraí. 

There are existing mechanisms to uphold high standards. A major concern with the use of the exempted development category is that safety and standards will become unenforceable. Safety and standards are important. Building regulations could be enforced, as they currently are with non-exempted development, through a system of certificates of compliance. 

Building control data could be used to enhance enforcement and enable evaluation. Following a recommendation of the National Competitiveness and Productivity Council, rectifying the deficiencies in the collection of data surrounding the Building Control and Management System (BCMS) would enable ongoing evaluation of the policy. More reliable data would enable planning authorities to better enforce building standards. 

Homeowners and contractors have a strong incentive to comply with the building regulations. The current system requires contractors to issue a certificate of compliance. Selling the home with uncertified works would render the development non-exempted which would make selling the home difficult and potentially very costly. Contractors are liable for the standard of work carried out on development, providing a further incentive for compliance.

Enforcement and compliance could be enabled through minor amendments to the Building Control Regulations. Existing opt-outs of the building regulations should be removed for seomraí, to ensure high standards and data collection. Article 9 and Article 20F of the Principal Regulations give the owner of some works which involve the construction of a new single dwelling, a single unit development, or a domestic extension, the facility to opt out of the requirement to obtain statutory certificates of compliance signed by a registered construction professional.¹⁵

Commencement and completion notices should be made mandatory for seomraí ensuring building compliance. Commencement and completion notices would allow policymakers to track the roll-out of the policy and enable its evaluation.

This regulatory oversight should ensure that the BCMS does not inhibit the supply of seomraí by making compliance overly complicated or costly to acquire. Recommendation 4 suggests one way in which design standards can be made seamless for homeowners.

Recommendation four: Pre-approved template design should be provided by the Department for Housing, Local Government, and Heritage or one of its agencies. 

Planning authorities can take the lead with a proactive approach providing building regulations compliant plans for seomraí construction. Following the successful roll-out of pre-approved plans in Seattle and across California, private firms could be invited to submit their designs for seomraí to planning authorities. Plans could take the local built context into account, ensuring seomraí fit into the broader visual context of the area.

First, the roll-out of design templates would encourage and enable the highest standards. Second, it would cut down significantly on costs for homeowners seeking to build a seomraí.

Recommendation five: Extend the rent a room scheme to incentivise homeowners to build a seomra.  

A seomraí policy could be enhanced by extending the rent-a-room scheme to all compliant seomraí. This would increase the viability of building seomraí for homeowners and incentivise their use for long-term rental.

Recommendation six: Floor space standards specific to seomraí should be set.

Progress Ireland recommends a minimum floor area no greater than 25 square metres for a one bedroom seomraí. Maximum exempted floor area should not exceed 40 square metres. Greater floor-areas should be permitted and encouraged but through the standard development process. Design templates would encourage high standards and expedite the planning process for more ambitious seomraí projects.

We believe that the small size of seomraí is their comparative advantage. There are two reasons for this: cost and demand.

Seomraí are affordable by design. Their small size is their strength. Comparatively small sizes not only bring down construction costs, they reduce energy costs for the occupant. 

The small size of seomraí enables single people to have a home of their own. Many young people who are currently ‘crammed’ into a small living space with strangers will see an increase in privacy and living space by moving into a seomra of their own. Similarly, young people living with their parents in small homes will see an increase in their privacy and living standards. 

Seomraí are popular not despite their small size but because of it. Seomraí remain a popular form of housing in jurisdictions with low or often no minimum size requirements. In California, the minimum floor area for ADUs is about 14 square metres. Yet they remain a popular form of housing. 

Second, several European capitals display minimum floor standards well below those commonly seen with ADUs. For instance, in our worked example, there is a floor plan for a seomra. At 25 square metres, it is notably above the minimum standards of several European capitals. A seomraí policy would provide an option that is currently not available. 

Some commentators have expressed a concern that allowing smaller homes to be built, such as seomraí, would entail a reduction of apartment sizes. However, apartment size provisions need not be dialled down to accommodate seomraí. A new size standard could be set regulating this unique typology, leaving apartment standards untouched. 

Recommendation seven: Retain existing building control requirements in relation to fire safety.

To ensure seomraí provision do not entail an unacceptable increase in fire risk, the existing fire guidance must be followed. The technical guidance on fire safety on the ‘Provision of Vehicle Access’ states: “For effective firefighting operations, fire brigade appliances should be able to get within 45 m of the principal entrance to the dwelling house.” 

Following this technical guidance, along with separation rules, will mean some restrictions on potential sites for seomraí construction. Crucially, the guidance does not support a ban of seomraí which fall within 45m of the principal entrance so long as there is sufficient side-passage access of approximately 750-800 millimetres. These fire safety requirements were an important element of Progress Ireland's modelling.

Recommendation eight: Encourage the use of public transport and reduce congestion by applying no minimum parking requirement.

Ensuring there are no minimum parking requirements would not only bring granny flat policy in line with peer countries but would also bring it in line with government policy here in Ireland. 

The report cited above by Dublin City Council notes the lack of provision of car parking spaces as a minor reason to retain the restriction on ‘granny flats’. Where car parking provisions were removed, in California, Portland, and Seattle, greater numbers of ADUs were delivered. Advocates for ADU policy in the United States frequently refer to minimum parking requirements as a ‘poison pill’ regulation, meaning that it inhibits supply. Ireland should learn from their success and follow their example.

1. The Report of the Housing Commission, p. 28; on different assumptions, the estimated structural housing demand for the next six years is between 38,000 to 50,000 per year depending on assumptions around household size and obsolescence rates. ↩︎
2. 40 per cent of 60,000, which is the official compact growth target. ↩︎
3.  In the United States, seomraí are generally referred to as accessory dwelling units or ADUs; in Canada, the category of ADU is broken down into secondary suite (an attached unit, typically in the basement) and laneway house (detached unit); in New Zealand and Australia, they are referred to as granny flats. Other names for seomraí include secondary units, second units, ancillary units, accessory apartments, accessory suites, backyard cottages, back houses, alley flats, carriage flats, coach houses, garage apartments, companion units, mother-in-law apartments, in-law units, in-law suites, and outlaw in-laws. See Anacker, K. B., & Niedt, C. (2023). Classifying Regulatory Approaches of Jurisdictions for Accessory Dwelling Units: The Case of Long Island. Journal of Planning Education and Research, 43(1), 60-80. ↩︎
4. According to Dublin City Council’s Habitat Mapping Project, “the most widespread habitat category in the DCC administrative area is gardens…, which cover 28% of the land area.” That is 3305 hectares or 33,051,889 square metres. Counting 265,193 gardens within the council’s borders, that gets us an average total garden area of 124.6 square metres. The category of gardens in their report also includes communal greenspace within apartment developments, so the real figure is likely a good deal lower than 124.6 square metres. ↩︎
5. See our worked examples ↩︎
6. These are split into two categories. First, ‘secondary suites’, which typically take the form of a basement unit. And second, ‘laneway houses’, which typically are a detached unit to the rear or side of the principal dwelling. ↩︎
7. To remove commercial units from our model, we removed all eircodes that were the registered address of a business. ↩︎
8. One of our recommendations is for seomraí to be included in the rent a room scheme. This scheme allows €14,000 of rent to be drawn down tax free. The market's gross yield is a pre-tax figure. In other words, the yield we have chosen is about twice as high as it would be, were it compared like-for-like with after-tax market yields. ↩︎
9. The Freddie Mac survey used rental listings and not permitting data. That means that some proportion of its findings were unpermitted or ‘informal’ ADUs. The study therefore overstates the number of legal ADUs; nevertheless, it indicates high levels of demand for ADUs. ↩︎
10. Building permits are here used to allow for cross-jurisdiction comparisons where there are differing standards of data collection for completions. ↩︎
11. This includes ADUs which are ‘rented’ to friends and family at no cost. ↩︎
12. In this report, low income means incomes in the range of 50-80 per cent of the median income of the area. ↩︎
13. In this report, low income means incomes in the range of 50-80 per cent of the median income of the area. ↩︎
14. For example, see Section 11.148 of Cork City Council’s Development plan, Section 4.10 of Volume 2 of Waterford’s Development plan, page 114 of Limerick’s Development Plan, Chapter 15 of Galway's Development Plan. Cork County Council is somewhat more favourable allowing for ancillary family accommodation in a wider range of situations, see (6.6.23). A granny flat for a family member is exempt from NPPR charges in Mayo, 2.9.2 and 4.15.2 but still can not be rented out. ↩︎
15. “Principal Regulations” means the Building Control Regulations 1997 (S.I. No. 496 of 1997) as amended by the Building Control (Amendment) Regulations 2000 (S.I. No. 10 of 2000), the Building Control (Amendment) Regulations 2004 (S.I. No. 85 of 2004), the Building Control (Amendment) Regulations 2009 (S.I. No. 351 of 2009), the Building Control (Amendment) Regulations 2014 (S.I. No. 9 of 2014), the Building Control (Amendment) (No.2) Regulations 2014 (S.I. No. 105 of 2014) and the Building Control (Amendment) Regulations 2015 (S.I. No. 243 of 2015). ↩︎