A central vacuum rough-in is the pipe, inlet backing plates, and low-voltage wire installed while the walls are open, in the same stage of the build as rough electrical and plumbing. It is the cheapest central vacuum installation you will ever have access to, and the least forgiving to get wrong, because once drywall goes up the pipe is fixed for the life of the house. This guide explains when it happens, what it includes, who coordinates with whom, and what you should insist the builder hand over.
When in the build it happens
Rough-in happens after framing is complete and before insulation and drywall, typically after the HVAC and plumbing rough-ins so the smaller vacuum pipe can route around ducts and drains. It takes a half day to a day for a typical house. If your builder has never scheduled one, tell them it slots in alongside rough electrical and that the vacuum installer needs to be on site before the insulation crew.
If the home has a slab with a finished floor planned on top of it and the builder wants under-slab pipe, that is a separate earlier step before the pour. Under-slab runs are protected in a larger outer sleeve and pressure tested before the sand and concrete go down. Most homes do not need this; attic and wall runs are simpler.
What the rough-in includes
The rough-in is everything that lives inside the walls and ceilings:
- 2 in thin-wall central vacuum pipe from each inlet location to the power unit location, with sweep fittings in the direction of airflow and a sweep tee where each branch joins the trunk.
- A backing plate (also called a mounting plate or rough-in plate) at each inlet, fastened to a stud at receptacle height, with a short 90 cemented to it and a plaster guard snapped over the opening so drywall mud and paint stay out.
- 20 AWG two-conductor low-voltage wire from each plate back to the unit location, tied to the pipe every 4 to 5 ft and spliced at each branch.
- Pipe straps on horizontal runs, nail plates where pipe passes within reach of drywall screws, and a steel sleeve or fire collar where the pipe passes through a fire-rated wall if local code requires one.
- A capped stub at the unit location with the wire coiled next to it.
- An exhaust stub through the exterior wall near the unit location, if the unit will be vented outside.
What it does not include is anything you can see after paint: inlet cover plates, the power unit, the hose, and the tools. Those are the trim-out, installed after flooring and paint so they are not damaged.
Planning the inlets while walls are open
Plan every inlet you might ever want, because the marginal cost of one more roughed-in inlet is a plate, a few fittings, and 20 ft of pipe. Walk the framed house with the floor plan and the inlet planning guide. The rule of thumb is one inlet per 600 to 1,000 sq ft so a 30 ft hose reaches every corner, but check it against the actual plan, because long halls and big open rooms break the rule in both directions.
Also rough in:
- A kitchen sweep inlet in the toe-kick of a base cabinet (specify which cabinet to the cabinet installer).
- A utility valve in the garage for the cars and the shop.
- One inlet at the top and one at the bottom of a stair, or one midway that reaches both.
- An inlet near the entry door and the mudroom.
Mark each location on the studs with the inlet height and a note on which side of the stud the plate goes. Photograph everything before insulation.
Coordinating with the electrician
The electrician provides a dedicated grounded receptacle at the power unit location, sized to the unit’s manual (many units specify a dedicated 15 A or 20 A, 120V circuit; some larger units are 240V). Give the electrician the unit’s spec sheet during rough electrical so the receptacle is in the right place and on the right circuit.
If you want direct-connect electric inlets, which power an electric powerhead through the hose without a separate cord, the electrician also runs 120V cable to each of those backing plates. There are two common designs: one has a junction box built into the plate and takes a standard cable feed; the other takes a short cable with a plug that snaps into the inlet cover. Either way it is line-voltage work and should be done by a licensed electrician under the permit, with the cable gauge matched to the circuit per the electrical code. Standard low-voltage inlets need none of this, and a pigtail hose that plugs into a nearby receptacle gives you an electric powerhead without wiring the inlets.
Coordinating with the drywaller and other trades
Tell the drywall crew that the plaster guards stay on until trim-out, and that each plate’s opening must be cut out cleanly, not buried. Buried inlets are the most common rough-in failure; the homeowner finds out when the trim-out installer counts plates and comes up one short. Nail plates protect pipe within 1-1/4 in of a stud face from drywall screws; ask that every penetration near the wall surface gets one.
Tell the insulation crew where the pipe is so they do not crush it. Tell the HVAC contractor that no vacuum pipe may share a duct. Tell the framer or finish carpenter which cabinet gets the sweep inlet.
Stubbing for a garage unit
The trunk should end where the power unit will hang: usually a garage or utility-room wall near an exterior wall for exhaust, away from the furnace and water heater, with floor clearance to pull the canister. Cap the stub, coil the wire, and have the electrician put the receptacle within reach of the unit’s cord. If the exhaust will go outside, run the exhaust stub through the wall now and cap it; a louvered vent cover goes on at trim-out. If the garage is detached or the unit location is a basement, the same rules apply.
Do not have the unit stubbed into an attic, closet, or any confined space. Manufacturers warn that heat and poor ventilation shorten motor life.
Planning for a retractable hose system
If you want a retractable hose system, decide now. The hose stores inside the pipe behind the inlet, so each retractable inlet needs a long run of pipe with large-radius fittings behind it and a specific inlet height and orientation. A standard rough-in cannot be converted to a retractable inlet without re-running that pipe. Read the retractable hose systems guide and give the installer the manufacturer’s installation guide before the rough-in is scheduled. A hybrid is common: one or two retractable inlets covering the main floor and standard inlets elsewhere.
What the builder should give you
Ask for, in writing or as files:
| Item | Why |
|---|---|
| Marked floor plan with every inlet, pipe route, tee, unit location, and exhaust route | You will need it the first time something clogs or when you add an inlet |
| Brand and model of the inlet plates and inlets | Cover plates and replacement inlets must match the plate |
| Photos of the open walls with pipe visible | Confirms routes and shows where nail plates went |
| Confirmation the system was leak tested before drywall | A split joint behind drywall is nearly impossible to find later |
| Count of plates roughed in versus plates trimmed out | Catches buried inlets |
| The unit’s electrical requirement and the receptacle circuit number | For the electrician who replaces the unit in 15 years |
Common mistakes
- Too few inlets, or none in the garage and kitchen, because the builder’s standard package had a set number.
- Inlets on exterior walls when an interior wall was available.
- Short 90s used in the run instead of sweeps, because a plumber did the pipe.
- The unit stubbed into a closet or attic.
- Plaster guards knocked off and the opening mudded over.
- No exhaust stub, so the unit vents into the garage forever.
- Not deciding on retractable hose until after drywall.
What to do next
Mark your inlets with the inlet planning guide, hand the builder the pipe and fittings guide so the pipe work meets the standard, and decide on your inlet type. If you will buy the unit later, the buying guide and sizing guide will match a unit to the pipe you roughed in. If the builder resists any of it, the cost to install page explains why roughing in now beats retrofitting later.
Frequently asked questions
When is a central vacuum roughed in during construction?
After framing, roofing, and window installation, in the same window as rough electrical, rough plumbing, and HVAC, and before insulation and drywall. It is usually scheduled after the plumber and HVAC contractor so the vacuum pipe can route around their larger ducts and drains.
What is included in a central vacuum rough-in?
The 2 in pipe from each inlet location to the power unit location, the fittings, a backing plate with a plaster guard at each inlet, the low-voltage wire run to each plate and back to the unit location, pipe straps, and a capped stub where the unit will hang. The inlet cover plates, hose, attachments, and the power unit itself are installed at trim-out after paint.
Should I rough in a central vacuum even if I am not buying the unit yet?
Yes. The pipe and plates are the cheap, invasive part, and they are far more expensive to add once the drywall is up. Many homeowners rough in during construction and buy the power unit and hose later. The stub at the unit location gets capped and the wire gets coiled until then.
How many inlets should be roughed in?
Enough that a 30 ft hose from each reaches every corner of the house, usually one inlet per 600 to 1,000 sq ft of living space depending on the floor plan. Add a sweep inlet in the kitchen toe-kick and a utility valve in the garage. When in doubt, add one more; a roughed-in inlet that is never trimmed out costs almost nothing.
Does a central vacuum rough-in need an electrician?
The low-voltage wire does not; the vacuum installer runs it. The electrician provides a dedicated grounded receptacle where the power unit will hang, and if you choose direct-connect electric inlets that power the hose, the electrician runs 120V cable to each of those backing plates. That is line-voltage work and should be done by a licensed electrician under the electrical permit.
Can Hide-A-Hose be added later if I rough in a standard system?
Not easily. Retractable hose systems store the hose in the pipe behind the inlet, so they need a longer, straighter run of pipe with large-radius fittings behind each inlet. If you might want one, rough in those inlet locations to the retractable system's specifications now. The retractable hose guide explains the constraints.
What should the builder give me when the rough-in is done?
A plan showing each inlet location, the pipe routes, the unit location, and the exhaust route; the brand and part numbers of the inlets and plates; confirmation that the pipe was tested for leaks before drywall; and photos of the open walls. Keep all of it with the house documents.