What an MCST is and what it can say about your aircon
Most condo owners meet their MCST at the worst moment: an installer already on site, told to stop. The letter or the call feels like an opinion, and part of it usually is. Telling that part from the part with force behind it decides how you answer.
By Team Snowflake | Updated 6 Aug 2026
Where an MCST comes from
A management corporation is not something a condo decides to set up. It comes into being on the date the strata title application for the development is registered. Its members are the owners of every lot in that plan. There is no joining and no opting out. Buying a unit makes you one of its members, and selling ends that.
It is a body corporate, which is why it carries a number rather than a brand. Its formal name is "The Management Corporation" followed by the strata title plan number. That number is the MCST reference printed on the notices you receive. Body corporate status also means it holds contracts and can sue and be sued in its own name. A requirement it issues is not the view of whoever happens to staff the office.
The corporation acts through a council, elected by the owners at each annual general meeting. Council members are owners of lots in the development, or the immediate family and company nominees an owner puts forward. They are volunteers with day jobs, and the seats change hands regularly. An answer a previous owner was given is not a reliable guide to the answer you will get now.
The managing agent is an appointment rather than the corporation itself. Most developments engage a firm to run the office, collect contributions and handle correspondence. That firm acts on the corporation's behalf, within whatever it has been authorised to do. So the person at the counter telling you the works cannot proceed is usually relaying a position rather than setting one. Keep that separation in mind when a refusal starts to sound like taste instead of rule.
None of this applies to an HDB flat, which has no management corporation. Common property in an HDB estate is managed by the town council for that town. That is a different body under different legislation, so the framework below stops at private strata housing.
The common property line is the hinge
Almost every aircon dispute in a condo turns on one boundary. The legislation treats common property as the parts of the land and building not comprised in any lot, and used or capable of being used by the occupiers of two or more lots. What sits inside your lot is yours. Everything else is held in common, and the corporation has the control, management and administration of it.
That definition reaches further than lobbies and car parks. It picks up the pipes, wires, cables and ducts serving two or more units, or servicing the common property. It picks up the structural elements of the building, and the waterproof membrane attached to an external wall or roof. The examples written into the legislation include external walls, roofs and facades used by occupiers of two or more units. A riser passing your unit on its way to others does not become yours because it runs inside your wall.
So an installation can be almost wholly within your lot and still need a conversation. The indoor units, the pipe run and the trunking inside your walls sit on your side of the line. The hole cut through the external wall does not. Nor does the bracket fixed to the facade, a condenser standing outside the lot boundary, or condensate discharging into a shared stack. One straightforward job crosses back and forth several times.
Where the line actually falls is set by the strata title plan for your own development, not by a general rule. Ledges are the usual source of disagreement. Some are drawn inside the lot and some are not, and two neighbouring estates can be drawn differently on the same question. The plan settles it, and the management office holds a copy.
| The part in question | Usually sits | What that changes |
|---|---|---|
| The part in questionIndoor units and the pipe run inside your walls | Usually sitsWithin the lot | What that changesYours to specify, subject to by-laws on hours and noise |
| The part in questionThe external wall face, the facade and the roof | Usually sitsCommon property | What that changesPenetrations and fixings become an approval matter |
| The part in questionRisers and ducts serving more than one unit | Usually sitsCommon property | What that changesRouting through them is not an owner's decision |
| The part in questionThe ledge or platform the condenser stands on | Usually sitsDecided by the strata title plan, either way | What that changesRead the plan before assuming the spot is yours |
| The part in questionThe stack the condensate finally discharges into | Usually sitsCommon property where several units share it | What that changesWhere the water ends up becomes a shared concern |
Why a hole in a wall becomes the corporation's business
The corporation is not being territorial about the facade. It carries a standing duty to maintain the common property and keep it in good and serviceable repair. That duty does not pause because an owner's contractor made the opening. Anything cut through, fixed to, or hung off shared structure becomes something the corporation is answerable for later.
The duty reaches the edges of your unit as well. Doors, windows and permanent covers over openings in walls fall to the corporation to maintain where one side of them is common property. So the external face of the wall your pipes pass through is generally on its list rather than yours. That is the practical reason approval attaches to a penetration which feels entirely private from the inside.
By-laws are the rulebook, and yours are not the next condo's
Every parcel in a strata title plan is regulated by by-laws, and by-laws are where the corporation's practical authority sits. Two layers stack on top of each other. A prescribed set, made by regulation, runs across developments. Above that, a corporation can make by-laws of its own by special resolution of the owners, so long as they do not contradict the prescribed set.
The second layer is why the honest answer to almost any question here is to read yours. Renovation hours, contractor requirements, restrictions on which parts of the common property may be used, and architectural guidance are all matters an estate can settle for itself. Something genuinely binding in one condo may simply not exist in the one across the road. An installer describing what condos generally allow is describing a habit, not your building.
A by-law the corporation makes has no force until a copy has been lodged with the Commissioner of Buildings. That is worth knowing when a requirement sounds invented on the spot. By-laws also bind more people than the owner. They bind the corporation itself, the owners, and any mortgagee in possession, lessee or occupier of a lot. A lease is treated as containing the tenant's agreement to comply with them.
Reading them is not a favour anyone is doing you. The corporation has to keep a record of the by-laws in force and put them where owners can see them. That means a notice board on the common property, and viewing at its office. It also has to supply an owner with a copy on written request. Asking for that copy costs nothing, and it is the step most owners skip before booking a contractor.
Not everything issued by a management office is a by-law. Renovation guidelines, house rules and standard forms are frequently administrative practice built on top of the by-laws rather than by-laws in their own right. That does not make them safe to ignore, and a contractor who disregards them will still be stopped at the gate. It changes the question worth asking, which is which by-law or condition a particular requirement rests on.
What a by-law cannot reach
The by-law power is broad without being unlimited, and two limits are written into the legislation itself. A by-law cannot prohibit or restrict the transfer, lease, mortgage or inheritance of a lot. It also cannot destroy or modify an easement created by or under the strata legislation. Those are the outer walls of the power, and it helps to know they exist.
The limit that comes up more often is quieter. A by-law made by a corporation cannot be inconsistent with the prescribed set, so a locally written rule cannot quietly overwrite a prescribed one. Put alongside the lodgement requirement, that gives an owner two ordinary questions instead of an argument: which by-law a requirement comes from, and whether it has been lodged.
What can an MCST require before aircon works?
An MCST can reasonably require approval ahead of anything touching common property, evidence that the contractor is insured and licensed, appointed working hours, and making good afterwards. A deposit against damage sits alongside those in many developments. Appointed hours exist to keep drilling out of a neighbour's evening rather than to obstruct anyone. None of it signals a difficult council.
Knowing why each requirement exists tells you which ones will move and which will not. Approval exists because the works touch property the corporation is obliged to maintain. The insurance condition exists because damage to that property lands on the corporation and, through it, on every owner in the estate. Making good exists for the same reason. These are not opening positions in a negotiation.
Requirements get harder to justify when they attach to something wholly inside your lot, or when nobody can name their source. A condition about how the outside of the building looks has an obvious basis. A condition about which brand of equipment you may install behind your own front door is harder to place. Neither observation is licence to proceed regardless, and both are fair things to raise politely.
The tell is usually in how a requirement arrives. One with force behind it can be pointed at, and the office can tell you where to read it. A preference tends to turn up as a general statement about what is not allowed here, with nothing behind it that can be produced. Asking which by-law or condition applies is not a confrontation, and either answer is useful.
| What is being asked for | Where it usually comes from | What to ask the office for |
|---|---|---|
| What is being asked forApproval before any works start | Where it usually comes fromControl of the common property being touched | What to ask the office forThe approval in writing, naming the works |
| What is being asked forContractor insurance and licensing | Where it usually comes fromLiability for damage to shared property | What to ask the office forWhich cover is needed, and in whose name |
| What is being asked forAppointed working hours | Where it usually comes fromBy-laws on use and enjoyment of the parcel | What to ask the office forThe permitted windows, stated in writing |
| What is being asked forMaking good after the works | Where it usually comes fromThe same liability for shared property | What to ask the office forWhat counts as made good, agreed beforehand |
| What is being asked forA restriction on where the condenser may stand | Where it usually comes fromBy-laws, or the lot boundary on the plan | What to ask the office forThe by-law or plan reference it rests on |
What to get in writing before you commit
Get the approval itself in writing, and make sure it names the works. Verbal clearance at a counter is not something you can produce later, when a different officer or a newly elected council asks why the condenser is where it is. Written approval naming the position, the scope and the date is what survives a change of managing agent, and managing agents do change.
Ask for the by-laws in force rather than a summary of them. The corporation has to supply a copy on request, and reading the text takes less effort than arguing later over somebody's paraphrase of it. Alongside that, ask which by-law or condition each requirement rests on. Two sentences from the office at this stage prevent a second filing further down the line.
Ask where the lot boundary runs on the ledge you intend to use. That is a strata title plan question rather than a matter of preference, and the office can answer it from the plan it already holds. It is also the one fact that decides whether the condenser position is yours to choose or something you are asking permission for.
If an installer waves off approval because the last job in the estate went ahead without it, treat that as a reason to check rather than a clearance. Works that were never challenged are not works that were approved. A letter can arrive well after everyone has forgotten the installation, and it lands on the owner rather than the contractor who packed up and left.
Three neighbouring subjects sit outside this page. The admin sequence for a private install belongs to the condo installation checklist: the forms, the scope file and the timing. Lobby, function-room and management-office units are condo common-area aircon, which the corporation maintains itself rather than approving. Where a tenant occupies the flat, rental aircon responsibility is a separate split and does not change who the by-laws bind.
By-laws differ from one development to the next, and this page is orientation rather than legal advice. The governing statute is the Building (Strata Management) Act 2004, still widely known by its former name, the Building Maintenance and Strata Management Act. What governs your situation, though, is the set of by-laws held by your own management office, and the boundary drawn on your own strata title plan. Read both before signing anything.
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