Non-standard construction
Only a Cornwall extension is built in concrete block. Why does a visual note still not award a mundic class?
A visual note still does not award a mundic class because a home survey does not drill cores or award Class A, B or C. Only the Cornwall extension is described as concrete block, and that description is what the eye could see. The visit did not test the concrete. RICS guidance on the mundic problem is for surveyors in the south west, and Cornwall Council describes a test it does not carry out on this visit. The note records blockwork. It does not attach a class.
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?
Mundic trouble is about the material inside certain concrete blocks, which a surface look cannot grade. An extension can be block while the older house is stone or brick, and that difference does not promote the extension into a classed result or clear it. Crumbs, a sound face or a tidy render are still appearances. Class letters belong to a separate testing process. Writing “concrete block” is a construction note, not that process.
Ask the solicitor whether any core test of the extension already exists, and who instructed it. Cornwall Council describes the test and does not provide it, so the papers should name a separate instruction if one was done. A lender may want that evidence rather than this visual note. The home survey will not drill the extension or add a class letter. Keep any later test as its own document.
What should you ask your surveyor?
- Which walls are described as the concrete-block extension?
- Does the report stay visual, with no core and no class?
- What wording keeps the older house separate from the extension?
What are the typical next steps?
- Read the block note as visual only.
- Ask the solicitor whether a core test already exists.
- Keep any later test apart from this home survey.
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 stone main house clear the extension?
No. A stone or brick main house does not award a class to the concrete-block extension, and it does not exempt it. The survey only recorded what the extension appeared to be built in. It did not drill cores or award Class A, B or C. The extension remains unclassified by this visit.
Can the seller’s builder award a class from the same walls?
No. A builder walking the same extension has still not done the core test Cornwall Council describes. A home survey does not drill cores or award Class A, B or C, and a casual look does not either. Any class would have to come from that separate test, not from this note that the extension is concrete block.