Building regulations question on zoning after extension

[Readingplumber]

Hello plumbers,

I know that the regulations state that a building exceeding 150m squared must be zoned.

My question is a house built in 1988 has just had an extension and it now takes it over the 150m squared area currently there is a y plan system do I have to now convert it to a zoned system or would just adding TRVs throughout do it on the extended bits meet the regulations?

Thanks

Readingplumber

 

[ShaunCorbs]

Needs converting to s + plan