Electrics and gas
An anti-vibration mat under the outdoor unit is crushed flat. Has noise been measured?
Noise has not been measured. The anti-vibration mat under the outdoor unit is crushed flat, which means the pad no longer has its thickness. A crushed mat can stop isolating the machine from the base. The survey saw the flattening. It did not meter sound and it did not state a noise limit. The condition of the mat is a visual defect. The noise of the unit, and whether the mat still does its job, stays unmeasured. Do not invent a decibel figure or a boundary distance from a flattened pad.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
These mats are compressible pads meant to keep vibration out of the wall. Once they are squashed solid, the unit sits as if the pad were not there. That is enough to record. It does not tell you how loud the fan is, how the sound travels to next door, or whether the machine is out of balance. A noise test uses instruments. None were used. Approved Document L is energy-performance guidance for building work, not a noise test, and this visit does not issue a building-regulations certificate.
The Boiler Upgrade Scheme is a grant route in England and Wales toward a heat pump or biomass boiler, not in Scotland or Northern Ireland. A crushed mat does not decide eligibility, and the survey quotes no grant figure. Ask an installer to inspect the mounting if you want the pad replaced and the unit checked. Tell a lender noise was not measured. Do not tell a neighbour a number for the sound. The only firm point is the mat seen crushed flat.
What should you ask your surveyor?
- Was noise from the outdoor unit measured?
- Does a crushed mat by itself state a noise limit?
- Has the survey invented a boundary distance for the unit?
What are the typical next steps?
- Treat the mat as crushed, and noise as unmeasured.
- Do not quote a sound figure the visit never took.
- Ask an installer to check the mounting if the pad must be replaced.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
Does a flattened pad prove the unit is louder than a set limit?
No. No limit was set or measured on this visit, and inventing one would be wrong. A crushed mat means the isolator has lost its thickness. Loudness is a separate measurement that was not made. The unit might be quiet or noisy. The survey cannot say which. Record the mat. Leave sound unquantified until someone actually meters it.
Was the pump's efficiency read from the condition of the mat?
No. Efficiency was not measured, and a mat is not a temperature or a power reading. The pad being flat says something about vibration isolation, not about how efficiently the heat pump heats water. The survey did not run a performance test. Approved Document L was not applied as a certificate. The mat is a mounting defect, nothing more.