The Housing Board advises homeowners to follow the guidelines below so that renovation works can be carried out legally:

To carry out renovation works in an HDB flat, including those that do not require a renovation permit, flat owners are required to engage an HDB Registered Renovation Contractor (RRC).

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The list of HDB RRCs is available on the HDB InfoWEB at www.hdb.gov.sg HDB flat owners can also obtain the list of HDB RRCs through their mobile phones.

Users can download the Mobile @ HDB app on their phones or access the services through http://mobile.hdb.gov.sg

For renovation work such as demolition of walls, contractors must electronically submit the floor plan showing the proposed renovation works together with the application for renovation works on behalf of flat owners to HDB for approval.

More information is available on the HDB website.

Flat owners must ensure that the renovation works carried out by their contractors are in accordance with the approved renovation permits and guidelines.

Flat owners are given information booklets such as a renovation guide and electrical guide for HDB flats when they collect their keys from HDB.

This information is also available on the HDB InfoWEB under the section Living in HDB flats >Home Renovation >Knowing the Guidelines.

To minimise inconvenience to neighbours, noisy renovation work like demolition of walls, removing wall and floor finishes, cutting of tiles and drilling works must be done between 9am and 5pm daily on weekdays.

Such works are not permitted on weekends or public holidays.

Contractors must also keep neighbours informed by giving them advance notice on the works that will be carried out, as well as display the notice of renovation work outside the flat until all the renovation work is completed.

More details can be found on the HDB website.

Mr Felix Setiawan, 30, a designer with Chew Interior Design, said they submit their renovation plans for evaluation by the Building & Construction Authority (BCA) or HDB before they start work.

He said: "To get around the hacking restriction, we sometimes propose putting up a divider, or just hack the wall to half its height to make the room brighter.

"It all depends on the situation as every owner wants something different, so we try to accommodate them."

Designer Bing Mendoza, 31, from DES Design Solutions, said their staff always follow the BCA guidelines.

They also help their clients go through the approval process.

An example would be the limit on the total floor area.

Said Mr Kenneth Ng, 36, a spokesman for I-deal House: "We usually educate our clients, since we know what the BCA would approve, and explain other designs if what the clients propose is unsuitable or illegal."

Said Mr Eddie Lua, 33, a spokesman for NorthWest Interior Design: "We sometimes encounter such requests (for illegal renovation works), as customers often don't know the requirements.

"In such cases, we would propose another design. All the design plans will be submitted to BCA for its approval." Other key points to note

You've got the keys to your flat and you're keen to start on your renovations.

But there are some things that homeowners should know before hacking that first wall.

Mr Lawrence Lee, 42, development manager in LB Property, said homeowners can check by visiting the HDB website or town council offices.

All HDB licensed contractors should be able to advise on what can or cannot be done with or without permission.

Dream home: Decor do's & don'ts Click on thumbnail to view

Other key points to note

Here's a list of renovation works that are not allowed in HDB flats:

Hacking and removal of structural members such as reinforced concrete wall, columns, beams and staircases within maisonette flats

Loading of the floor slab with a load greater than 150kg for every m sq of floor area Plastering of ceilings

Partitioning the unit with combustible or toxic emission materials such as plywood or plastics Using concrete to raise the floor level beyond the allowable thickness of 50mm.

Extending the floor area by covering over void deck areas

Constructing a water tank in the bathroom unless it is a ready-made fibreglass bathtub

Repositioning or enlarging the opening of the rubbish bin chute

Painting external parts of the building

Installing fixtures outside the unit

Installing casement windows where the unit's facade is facing common corridor

Laying floor finishes outside the entrance door without a recess area or step

And here's why some of the renovations works are not allowed:

They may overload the structure, which may in turn affect the structural integrity and safety of the building

They will affect the external facade/form of the building or public safety

They will create a public nuisance, pose a fire hazard or encroach on public areas

They will infringe the lease agreement, relevant statutory regulations or requirements

For owners of condominiums and private apartments, Mr Lee said they should get permission from the Management Committee Strata Title or Managing Office before proceeding with any renovations.

The MCST or Managing Office will usually have a list of guidelines derived from the databases of the relevant authorities and advice from the project consultants.

Information is also available at the Urban Redevelopment Authority (URA) and Building Contruction Authority (BCA) websites.

This article was first published in The New Paper.