A peer review has found the main building at Hutt Hospital is in better shape than first thought.

In May, Hutt Valley DHB revealed the Heretaunga Block had a 15 per cent New Building Standard (NBS) rating making it earthquake-prone. Several structural and non-structural elements in the building were given this low rating.

At that time the DHB said patients and services would eventually have to be moved out of the building.

But a peer review of that draft detailed seismic assessment has since been completed, finding the precast concrete façade panels are now the only part of the building rated at 15 per cent NBS.

However, the DHB advised in an update today this did not change the overall status of the building under the law.

A building's rating is determined by its weakest part so even if the issue is localised, or just one element is below 34 per cent NBS, the site's overall score is affected and still considered earthquake-prone.

While other elements in the building were no longer rated at 15 per cent NBS, the DHB said they were still considered an earthquake risk.

"We are therefore recommending the Board confirms our earlier decision to relocate services out of the building as soon as reasonably practicable."

The precast concrete façade panels are on the building's exterior. The DHB said it was awaiting further engineering advice on how it could further mitigate or remediate the risk.

A fence is already in place around the Heretaunga Block.

On Wednesday the Hutt Valley and Capital Coast District Health Boards will consider the final draft detailed seismic assessment.

There are 210 physical bed spaces in the Heretaunga Block, which account for a quarter of hospital beds in the region.

It is not unusual for peer-reviews to reach a different conclusion to the initial assessment.

Engineering is after all not an exact science.

For example, an initial assessment of Wellington City Council's Freyberg Pool found the building was earthquake-prone, but was rated at 40 per cent NBS after engineering consultancy firm Beca was brought in for a second opinion.

Engineers involved in that decision acknowledged it was easy to be conservative but "really difficult" to be realistic.

Speaking about Freyberg Pool, Beca's building structures chief engineer Rob Jury said engineers tried to get scores and ratings of buildings as high as they could reasonable justify.

"You must go down every avenue I think because as I say, you've got to give these buildings the best chance basically without over-egging it."