Grave Subsidence Information
Why do Graves Sink?
Grave subsidence refers to the appearance of graves ‘sinking’.
This is an entirely natural process caused by loosened soil settling into place.
Grave subsidence is a process that Council manages and rectifies, and it should not be cause for concern.
A grave can take up to 12 months to settle.
What causes grave subsidence?
The excavation of a grave results in the loosening of the excavated material.
When soil is replaced into a grave, it will inevitably contain more air pockets than the compacted soil before excavation.
Over time, a backfilled grave will ‘sink’ as the air pockets escape and the soil settles; this is absolutely natural and practically unavoidable, especially in wet weather.
The amount and frequency of grave sinkage depends upon numerous factors, including:
- Nature of the backfilled soil, heavy clay soils take longer to settle.
- Nature of the surrounding ground
- Depth of excavation
- Amount of rain, or rainwater runoff
- Groundwater levels
Ground subsidence is more likely after an extreme rainfall events or excessive rainfall over a prolonged period of time.
Why don’t the cemetery compact the graves?
The sinkage of the surface of a grave can cause distress to the bereaved, it is a ‘natural’ phenomenon that affects all cemeteries.
Following the backfilling of any excavation, unless sufficient pressure is applied to thoroughly compact the backfilled material to exclude air spaces, the backfilled material sinks.
However, in the case of cemeteries, it would not be appropriate to apply such pressure to graves as it would crush the coffin.
What happens after the burial?
Following the funeral, the grave is backfilled using the soil excavated from it.
A certain amount of ‘mounding up’ of the grave takes place in anticipation of ground sinkage.
In most of our cemeteries the ‘mound’ is a thick clay material, which is the soil excavated from the grave.
During the weeks after the burial the Council staff will conduct regular checks of recently backfilled graves, as well as monitoring graves after periods of rainfall.
After identifying which graves need top ups, staff will schedule time to carry out these works.
Subsided graves will be topped up by our staff until the soil has compacted naturally. A grave may need to be topped up on several occasions over an extended period of time.
Once a grave has stopped subsiding and has stabilised, a layer of topsoil and grass seed will be placed over the grave area to ensure the topsoil does not erode.
What to do if you notice grave subsidence
You can help us manage grave subsidence by submitting a request for a grave top up.
To assist the process, please take note of the grave’s location and other details such as the name on the memorial or area of the cemetery so that we can locate the grave on our mapping system.
After identifying the grave, we will log a maintenance request and Council staff will schedule it in to a series of top ups.
Weather permitting, most top ups are completed within ten days.
For further information
Please contact our Cemetery Office on T: 028 9335 8232
- Grave Subsidence Information Sheet (pdf 130 KB)