Owners of landed homes who are planning to tear down their properties and rebuild them will get more flexibility in the design of their interiors from May 11.
The new rules will also affect developers of landed homes.
But the Urban Redevelopment Authority (URA) will allow minor Additions and Alterations works to existing landed houses under current guidelines as well.
The change allows architects to have more leeway over the design of the interior, as long as the overall external size of the home still fits within a three-dimensional limit, or "envelope".
For example, existing rules state that the third storey must be set back an additional 1m from the first and second storeys. But under the new guidelines, there is no such requirement. This means that the third storey can be flush with the lower floors and be more spacious.
Another change is the floor-to-floor height requirement, which is currently 4.5m for the first storey, 3.6m for the second and 3.6m for the third. But under the new rules, this will be up to the owner's preferences.
This means that owners can also now vary floor-to-ceiling heights, adding more mezzanine floors should they choose.
"Owners can layer their homes creatively, to bring in natural light and ventilation," National Development Minister Khaw Boon Wan wrote on his blog yesterday.
"(The new guidelines) are most likely to benefit those who live in intermediate terraces."
However, the total maximum permissible height has been reduced. For three-storey homes, the total height has been cut from 17.7m to 15.5m, while the height for two-storey homes has come down from 14.1m to 12m.
These numbers include an additional 3.5m allowed for an attic.
URA noted that the new envelope heights were modelled after completed housing projects, where the height of a typical three-storey house is 15.5m. Not many homes build up to the maximum height of 17.7m.
The rules are being introduced on the back of a pilot scheme in Sembawang Greenvale. The 65 houses in the scheme - a mix of 55 terrace and 10 detached homes - were completed in May. The majority have been sold.
The URA conducted a public consultation exercise that started from 2007, engaging landed housing residents, architects, developers and other stakeholders.
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