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What changes when the building is shared.
Six things that are ordinary in a townhouse or a condominium and simply do not arise in a detached house. None of them is about the equipment.
The wall does not stop the noise you are worried about.
A party wall between two homes is built to stop sound travelling through the air, and it does that well. Structure-borne sound is a different problem and the wall does very little about it.
Structure-borne means the vibration is travelling through the building rather than through the air in it. A compressor bolted rigidly to a deck couples into the deck. A duct resting against a stud couples into the wall. A line set strapped hard to a joist carries a low rumble two rooms away and into the unit next door, where it arrives as a hum nobody can locate.
That is why "buy a quieter unit" so often fails. The machine was never the loudest part of the path.
The fix is to break the path. Isolation pads or springs under equipment, flexible connectors where duct meets the air handler, resilient hangers instead of rigid straps, sleeves at every penetration, and a condensate pump moved off the shared wall. It is unglamorous and it is usually a fraction of the cost of the replacement somebody was considering.
Three questions that locate it
Is it worse at night? Usually means structure-borne — the background level has dropped and a low-frequency path is left exposed.
Can they hear it with their windows shut? If yes, it is almost certainly not coming through the air from outside.
Does it stop the instant the system stops? If it fades over a second or two, look at duct and airflow rather than at the compressor.
The one we cannot solve
Occasionally the equipment sits somewhere the building never should have used — directly on a lightweight deck above a bedroom, for example. Isolation improves it and does not eliminate it. We will say so, and price what relocating would involve, rather than selling a sequence of partial fixes.
There is no side yard.
So the outdoor unit goes in one of four places, and which of them exists is a property of the building rather than a choice.
- Roof
- Common, and always common areaMeans roof access, means somebody's warranty on the membrane, and means vibration into the structure below. Approval is certain to be required and the association will care about how the unit is supported and how the penetration is flashed.
- Podium deck
- Above the parking, below the homesUsually the easiest access of the four and the most sensitive to vibration, because the deck is a structure with dwellings on it. Isolation is not optional here.
- Balcony or patio
- Convenient, visible, and often restrictedScreening requirements, condensate routing that must not drop onto anyone below, and clearances that a small balcony makes genuinely tight. Frequently the position the association has the most to say about.
- Designated pad
- A small allocated slab at ground levelThe nearest thing to a detached-house arrangement, and the rarest in newer stock. Check whether it is exclusive-use common area rather than yours — it usually is, and that changes who approves what.
Weight and access come first
Before any of the above is discussed as a preference, we check two practical things: whether the unit can physically be got to that position, and whether the position will take the load. A roof that needs a crane lift is a different project from one with a service stair.
Everything arrives through space somebody else owns.
A corridor, a lobby, a lift, a loading bay, a shared drive. In a detached house this is a driveway. Here it is the association's property and its condition is your liability while you are using it.
So access is planned rather than improvised. Before the first day we agree with the management: which entrance, which lift and when it can be booked, where the van can stand, what protection goes down in corridors and lobbies, and what hours are acceptable.
And a rule we do not bend: nothing is left in common area overnight. Not a compressor, not a ladder, not a pallet of duct. It goes into the unit or back in the van. Every board that has dealt with a contractor who did otherwise knows exactly why that sentence is here.
Walls between homes are assemblies, not just walls.
The wall or floor between two dwellings is usually a fire-rated assembly, and anything passing through it has to be sealed so the rating is maintained.
That is routine, well-understood work. It is also work that gets skipped by people who do not usually build in attached housing, and the consequence is not visible from the finished side — which is exactly why it is worth saying out loud.
The same applies to the exterior envelope. A penetration through a wall that is part of the building's weather barrier has to be sealed and flashed properly, and on most properties the association is entitled to know how. It is also the item most likely to appear in a submittal condition, because a leak that starts at somebody's line-set penetration becomes everybody's problem.
Where a building has a proper chase we use it. Where it does not, the route is designed — not found on the day by whoever is holding the pipe.
The same floor plan, three different loads.
An interior unit with neighbours above, below and either side has one exposed wall. An end unit in the same building has three, plus a roof.
They are the same square footage and the same drawing, and they do not want the same equipment. The interior unit is buffered on five surfaces by other people's conditioned space; the end unit is a small detached house with a shared wall on one side.
Which means the honest answer to "what did my neighbour have fitted" is often "something that would be wrong for you". We calculate rather than match, and on a building where several owners replace within a few years of each other that is worth saying plainly.
The other thing this stock does: interior units are frequently over-cooled by their neighbours. A unit surrounded by others that all run air conditioning gains very little heat through those surfaces. Its own system spends the summer barely working, and if it was sized as though it were a detached home it short-cycles all year.
What we ask on the first visit
- Which surfaces are exposed and which are shared
- Which way the glazing faces and whether anything shades it
- Whether the unit is top floor, and what is above it
- Whether the neighbouring units are occupied and conditioned
- Where the return air is, and whether closed bedroom doors have a path
Somebody wrote down what you may do.
Your governing documents decide what is permitted, where it may go, what it may look like and who is responsible for it afterwards. They are the first thing we ask for.
What they contain varies enormously — two buildings a street apart can have entirely different rules about the same balcony. So we do not tell you what yours say. We read what you give us, design to it, and put the proposal in front of the association in the form it asks for.
And we will not start without a written yes. Equipment installed without approval can be ordered removed at the owner's cost, and that is a conversation nobody wants to have standing in a finished unit.
What we are not
We are not lawyers and we do not interpret CC&Rs. If your documents are ambiguous about something that matters, the right answer is your board, your managing agent or your own counsel — not an HVAC contractor's reading of a clause. We will tell you exactly which sentence we are unsure about, which is a more useful thing than a confident guess.
Asked once people have read this far.
My unit is in the middle of the building. Do I need less capacity?
Often yes, and by more than people expect. An interior unit is buffered on most of its surfaces by other people's conditioned space, so its load is genuinely smaller than the same floor plan on the end of the row. That is a reason to calculate rather than to match whatever the neighbour bought — and a reason an oversized system is particularly common in this housing type.
Can I put the outdoor unit on my balcony?
Sometimes, and it depends on three things: whether the association permits it, whether the clearances the manufacturer requires actually fit, and where the condensate goes. The third one catches people — draining onto the walkway or the balcony below is a problem even where nobody has noticed yet. We check all three before proposing it.
The building has a shared system. Can I change my part of it?
That depends entirely on how the building was designed and what your documents say about the boundary between your unit and common area. Some properties have genuinely individual systems with a shared route; others have equipment that serves several units and is not yours to touch. Establishing which you have is the first thing we do, and occasionally the answer is that this is the association's project rather than yours.
Who is liable if my line-set penetration leaks in five years?
That is exactly the sort of thing a submittal should settle in writing before the work, and one of the reasons we prepare one. The common answer is that the owner is responsible for their own installation including the penetration, but it is not universal and it is not something to assume. If your documents are silent, ask the board to put an answer in the approval letter.
Do you work for associations directly, or only for owners?
Both. Owners are most of the work. We also take instructions from boards and managing agents — for common equipment, for scheduled service across several units, and reasonably often to give an independent view on whether a noise complaint is actually caused by what somebody thinks it is.
Send us the building, not just the problem.
The unit number, the floor, and whether there is an association. That is enough to know what kind of visit this is.