Non-standard construction
Render covers a house the survey calls Dorlonco and no panel was exposed. What concrete behind the render was not tested?
The concrete behind the render was not tested at all. The survey calls the house Dorlonco, a precast concrete system, and the render was left in place, so no panel was exposed. Naming the system records a construction the surveyor believes this is. It does not core the concrete, test its condition, or show the reinforcement. The survey has identified a rendered Dorlonco house from what could be seen without opening it. It has not tested the panels the render still hides.
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?
Dorlonco construction uses precast concrete panels, and a later render coat can cover the joints those panels give away. The surveyor may still name the type from the form of the house, the age, and details at openings or eaves. That name is an identification, not a laboratory result. Carbonation, cracking inside the panel, and the state of the steel inside it are not visible through an intact coat, and this visit did not cut the coat back. Untested means untested, even where the name is confident.
Tell the solicitor the construction is named and the concrete is untested. A specialist in non-standard houses can say what opening or sampling would involve, and a lender may ask for that separately. Do not treat smooth render as a test certificate. The survey has not measured the panels and has not decided they are sound because the coat is whole. Identification and testing remain two different steps.
What should you ask your surveyor?
- What did you see that led you to call the house Dorlonco without exposing a panel?
- Which concrete, if any, was actually visible rather than rendered over?
- Have you left the panels untested for condition and reinforcement?
What are the typical next steps?
- Read Dorlonco as a name for the system, not as a test of the concrete.
- Tell the solicitor no panel was exposed behind the render.
- Do not treat an intact coat as a clearance of the panels.
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
If the render is uncracked, has the concrete been tested?
No. Uncracked render is a face. The concrete behind it was not exposed and was not tested. A whole coat can hide a panel the survey has not seen. The Dorlonco name does not do that testing either. The panels remain unexamined behind the render.
Does naming the system measure the panels?
No. The name says what kind of house the survey believes this is. It does not measure strength, cover to the reinforcement, or cracking inside a panel. No panel was exposed. The concrete behind the render was not tested, whatever the system is called.