With plans drawn up and a permit granted from council, the estimated cost of the extension project sat at $147,000 and included purchasing of the buildings, relocation and renovation.
The total is now an estimated $182,126.
"As you can imagine, purchasing these two buildings significantly impacted on the books.
"What was already an expensive endeavour for KYS has now dramatically increased.
"The largest cost however is to Kapiti's youth, who will have to wait until funds are raised for the buildings to be completed."
Acting senior sergeant Chanel Chapman, from Kapiti police, said the matter was ongoing and involved Youth Aid.
"This means those being investigated are around 13 and 14 years old.
"At this stage there are still a number of youth to be spoken to in relation to this matter."
Ms Osborne said she believed those involved would not have damaged the buildings had they known they were going to KYS.
With every window in one of the buildings completely smashed and extensive damage made to most of the walls and ceilings, both buildings needed full re-glazing, gibbing, plastering and painting "just to get them back to their pre-damage condition".
Paraparaumu and Kapiti Rotary Clubs had offered to help with internal painting of the buildings, while KYS staff set up a Givealittle page for donations.
"What we thought we were getting is not what we got," Ms Osborne said.
"But we couldn't leave the buildings there because we'd already spent a substantial amount on clearing the space and we had a verbal agreement."
Ms Osborne said despite the disappointment, she looked forward to seeing the extensions unfold, to help with the growth and "shortage of space" at KYS.
"One of the buildings will be rented out to alternate education provider STR, who works with some of Kapiti's most vulnerable young people to support them back into education.
"It'll be a place for young people excluded from Paraparaumu and Kapiti Colleges to go because it hasn't had a base in the last few years, which isn't conducive to their learning.
"Having them here gives them a nice, stable base with lots of room for doing activities outside and generally providing them with that wrap-around service."
KYS currently has 5,200 local young people enrolled in its services, comprising 78 per cent of the Kapiti youth population.
Ms Osborne said she hoped a restorative justice process would take place once the people involved were identified.
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