Gas pipe-gas pressure-rendering-Joe Public confused !

I am your typical Joe Public, I can read about gas boilers and systems etc and then ask the Gassaferegister listed person to come and look and give me a quote for the work required. It is ME that pays the bill.
Installer A looks at the gas feed pipe from meter to boiler-10m distance-with take off for gas hob, and says that the present 15mm copper pipe will not do because it won't carry enough gas pressure and will need a 22mm pipe.
Installer B looks at same pipe and says that the concrete rendering over the Victorian brickwork that uses the 15mm copper pipe as an edge/finish line, about 8 inches above ground level, will not do as rendering corrodes the copper and will not get signed off. Rendering has been there for 20 yrs.

A said nothing about this rendering and B said nothing about gas pressure.

This Joe Public is now confused by the comments/non-comments of two registered, qualified installers.
Are they both correct , but missed a bit or what !!!???

Comments please.

Brian

The gas pipework will require upgrading for the new boiler anyway, regardless of a rendering issue. Depending on the boiler and total length of pipework and what fittings are involved in that run then it may even need some 28mm in there.

If I were you I would be more inclined to lean towards Installer A as he has given you the correct advice so far.

installer A, would not need to worry about the rendering because he is going to replace the gas pipe.

the gas pipe should be installed with stand off clips and sleeved wen passing through walls so the rendering shouldn't affect it as long as it is installed correctly

Standoff clips is one way coated or protected pipe can be put against walls with saddles .