The health board said the “additional precautionary measure” at the new Edinburgh Sick Kids would be undertaken by the private consortium IHSL, which owns the building.
It comes after IHSL advised some materials in the hospital’s cladding had not received a “low-risk classification”.
NHS Lothian was told this would have an impact on the spacing between "cavity barriers", which stop the spread of fire through wall cavities behind the cladding.
The health board insists the overall level of safety remains high and is not “significantly reduced”.
Earlier this year, he called for clarity about the safety of the cladding used on the hospital after it was claimed parts of it are covered in an Aluminium Composite Material (ACM) similar to that used on Grenfell Tower.
He said the issue around cavity barriers “is just the latest in a long line of building defects affecting this facility”.
Mr Cole-Hamilton added: “Health bosses are now suggesting that it will be sometime next year before action is taken. I think every patient, parent and staff member would have expected the Government and NHS Lothian to act with more haste.”
A Scottish Government spokesman insisted “no cladding of the type that was used in Grenfell Tower is used in any Scottish hospital”, including the Royal Hospital for Children and Young People (RHCYP), known locally as the Sick Kids.
He said: “There is a need for remedial work to ensure all cavity barriers in use at the RHCYP are fully compliant with safety regulations. We are working with NHS Lothian to ensure this work can be carried out as soon as possible.”
A public inquiry is looking into construction issues at both the new Sick Kids and the Queen Elizabeth University Hospital in Glasgow.
Jim Crombie, deputy chief executive of NHS Lothian, said: “The insulation, cladding and linings on the Royal Hospital for Children and Young People and Department of Clinical Neurosciences are compliant with fire safety regulations. NHS Lothian is finalising a programme of works with its PFI [private finance initiative] provider, IHSL Ltd, to reduce the spacing of cavity barriers from the current 20m intervals to 10m intervals as an additional precautionary measure.
“Whilst the materials are compliant, NHS Lothian was advised by IHSL that some materials in the cladding had not received a low-risk classification. The health board was told that the non-low risk materials used would have an impact on cavity spacing, but that the overall level of safety remains high and is not significantly reduced.
“To address space cavity recommendation, NHS Lothian received an initial work proposal from IHSL and detailed planning is currently underway with them as the building’s owner to undertake the works safely with minimum service disruption on a live hospital site. Works are anticipated to start next year, to avoid any adverse weather conditions.
“As a precautionary measure and despite assurances around the overall level of safety, robust risk assessments have nevertheless been carried out to further ensure the safety of patients, staff and visitors.”