Unknown Swilly - Grianan Aileach October 2006

In a response to the Donegal Democrat the Office of Public Works states that, ”The wall tops are secured with a cement finish in an effort to prevent frost damage and interference causing stone collapse and resultant risk to the visitor.” - Literature about wall building advises strongly, that walls, in particular walls with mortar/cement joints, have to be finished with covering stones on top stretching over the full thickness of the wall. It will prevent moisture from penetrating the mortar/cement and rain water forming lines on the surface. When frost sets in the moisture will expand causing cracks and allow even more moisture to be trapped, leading eventually to movements within the wall. The mortar/cement joints are unable to withstand this pressure and fall apart. Severe damage of the wall is the only and irrefutable result. The top of Grianan’s wall as well as the platform show clearly the exposed cement joints with no covering stones for protection.

The statement of the Office of Public Works also mentions that, “Due to the instability of the underlying surviving stonework modern reinforced concrete supports were inserted at the base of the rebuilt sections over the lintols of the internal passageways. All external walling would be constructed by OPW craftsmen to match Bernard’s design but with a sound central fill which would considerably improve the structure’s future stability.” - At the south-west facing part of the wall, the same section, which already collapsed three times over the last six years, it is possible to reach inside gaps and touch the concrete. This is the part of the wall which is most heavily exposed to the weather. The above mentioned process will set in of moisture expanding under cold conditions, causing structural damage.

And there is another aspect to be considered. Grianan Aileach was built as dry stone construction, which needs only a very low foundation, because its walls are flexible and can therefore adjust to movement. The use of cement and concrete have turned it into a static or inflexible wall, standing on a dry stone foundation. The construction of a static wall demands a different and more extensive foundation.

None of these problems would have occurred if Grianan Aileach would have remained a dry stone building.

The inconceivable ignorance of basic laws of physics will leave Grianan no other option but to collapse again. Under the circumstances it has to be declared unsafe. Signs of immediate collapse have been missed on previous occasions and might not always be visible in time, since concrete is embedded in a 12” thick wall.

Years of restoration under the charge of the Office of Public Works turned a historic dry stone monument into a modern building, changed the outside shape as well as the equal width of the platform into an irregular one and blocked access to the passageways. It also makes viewing very much at your “own risk” and “from the outside only”. Safe distance provided.

And finally, there still remains the mystery of the missing stones. When cement and concrete is used to rebuild a former dry stone wall, than there are stones left, if the wall is to retain its size. Such leftover stones from previous work form already an impressive pile on the south-west facing side of Grianan. On the 29th September repairs had finished at the gate section but not one leftover pebble in sight. What leaves only two conclusions; Grianan has grown or stones have been taken away. The latter comes with compliments of Murtagh O’Brian, King of Munster, who billeted “the stones of Aileach on the horses of the King of the West” in 1101.

"I never heard of the billeting of grit stones,

Though I heard of the billeting of companies,

Until the stones of Oileach were billeted

On the horses of the king of the West."

Annals of the Four Masters, Book II/ p 969; M1101.6

After "To the best of our knowledge there is no cement being used to repair the site at present.", what in its own way was not necessarily incorrect, since work had finished at my last visit on September 29 and therefore at the exact time of this email being written no cement was being used; I sent a few photos to the Donegal Democrat from May 2004, showing clearly cement/concrete between the stones. On October 3, 2006 I received an email from The Donegal Democrat, forwarding a second response of the Office of Public Works. Strangely enough, it was dated 3/09/06.

Attached the reponse from the Office of Public Works to the newspaper. I leave it the way it came. The mentioned Annual Report of Commissioners of Public Works 1907/08 is not available on their website nor on verbal request.

Grianan Aileach 3/09/06

As stated in the previous response, a local man, Dr. Walter Bernard rebuiltthe site of Grianan Aileach between 1874 and 1878. However, in the absence of archaeological evidence for its original appearance, he modelled the rebuild on the relatively intact Staigue Iron Age Fort in County Kerry.History of collapse and need for more permanent repair method

When the site came into State Care approximately thirty years later the restored walls were already in a dilapidated state with extensive collapse of the outer stonework. Despite OPW efforts to carry out patch repair work to the monument over the next 80 years the files show that Bernardís work was unstable and collapse was reoccurring on a regular basis.

In 1989, following another major collapse and short term patch repair work, OPW undertook to monitor the condition of the monument and investigate intervention methods that could stabilise the structure.

Immediately following the next collapse a specialist multi-disciplinary team was assembled by OPW to address the problem. In 2001, a detailed archaeological and engineering investigation was undertaken which revealed sections of the line of the ancient pre-restoration structure and confirmed the shape and outline of Bernardís work.

Due to the significant amenity value of Bernardís restored monument OPW considered that it would not be appropriate or feasible to dismantle and remove Bernardís restored stonework and to leave the site in its pre-restoration collapsed state. The engineer recommended that the bulging
sections of walling, which were liable to collapse should be dismantled and rebuilt to Bernardís inward sloping design. Due to the instability of the underlying surviving stonework modern reinforced concrete supports were inserted at the base of the rebuilt sections over the lintols of the
internal passageways. All external walling would be constructed by OPW craftsmen to match Bernardís design but with a sound central fill which would considerably improve the structureís future stability. The use of modern materials in the preservation of ancient structures is standard
conservation practise.
The wall tops are secured with a cement finish in an effort to prevent frost damage and interference causing stone collapse and resultant risk to the visitor.

Sample extracts from Derry Journal on OPW file ñ recording recurring damage to site:

29/12 /1989 ñ ìGrianan of Aileach badly damaged ì

16/5/1961 ñìGrianan damage to be repaired ì

14/4/1939 ñìVandalism at Aileachî

Useful historic references:

Detail description (with illustrations) of the site before Bernardís intervention in the Ordnance Survey Memoirs 1837

Description of Bernardís work in Proc. Of the Royal Irish Academy Volume 1Sec 2 1879

Detail Description of poor condition of site when taken into State Care In 76th Annual Report of Commissioners of Public Works 1907/08

Concrete or cement? - That's the question

October 8, 2006

2000

2003

Open Letter To The Taoiseach, May 2007

GRIANAN AILEACH FACING STRUCTURAL FAILURE