05 April, 2022

Theoretical Structural Archaeology - Thirty New Discoveries


  1. Introduction 

1.1 What I study 

  • I reverse engineer archaeological buildings & structures from posthole evidence.

  • Using  traditional architectural technical drawing, CAD, and deductive reasoning to build functionally accurate models.

  • Working with the complete scaled dataset to identify basic structural components.

  • I started in 1990 [1] & published online here since 2008. {so they are not all new}

  • Postholes are the most numerous archaeological features on certain types of sites.

  • Thus, Theoretical Structural Archaeology represents a set of analytical techniques for understanding certain archaeological data sets.

1.2 What qualifies as a discovery 

  • Insights & discoveries of potential national or international importance.

  • Completely original & not copied from other scholars or site reports. 

  • Outside of my primary work as a professional archaeologist. 

  • Work done in my own time.

1.3 Wider context of Theoretical Structural Archaeology

  • My basic methodology has been peer reviewed in the USA. [2]

  • Theoretical Structural Archaeology is maths & science based where possible. 

  • Models are refined by looking for errors, inconsistency and poor mathematical fit.

  • To the best of my knowledge I am the only UK archaeologist working on the interpretation of timber built environments. 

  • This was the basis of a PhD at Newcastle, but evidence based archaeology and science proved incompatible with image based post-processualism subjectivism.

1.4 Format - 30 page A4

Brief and concise summary of the insight, idea or discovery.

  • Details, definitions & Implications - maximum of six.

  • Summary or example illustration as space permits. {this is a very visual subject}.

  • To Fit on A4 sheet, ie. 30 Pages {+ this one}, in 3 groups;

  • Basic structural modelling {from c. 430 lecture / video slides} 1-7

  • Advanced Structural Models & Case Studies 8 - 22

  • Archaeology of Hadrian’s Wall { from 3 Videos + 120 lecture slides} 23 -30

2. Basic structural modelling 

2.1 Reverse Assembly Truss

The most important concept and the basis of any understanding of post built buildings is the difference between normal and reverse assembly. {sectional view}

  • A Truss is composed of a rafter pair with a horizontal Tie across the bottom.

  • This triangle is the basis of the roof as understood; a building is a roofed structure.

  • Assembly is the detailed order in which the structural components are put together; i.e. foundations first to thatch last. 

  • Normal Assembly; in a building with load bearing walls, the load of the roof is supported on a solid wall or timber frame, the roof truss and its tie sit on top.

  • Reversed Assembly; in a building where the mass of the roof is supported on posts, it is practical to place the posts directly under the ties.

  • This arrangement allows for;

  • Offset posts which simplified jointing

  • Lightweight wall construction

  • Still present in Far Eastern tradition, {performance in earthquakes}.

2.2 The Offset Tie

Apparent irregularity in the layout of posthole foundations can be explained as a product of offset jointing, which simplifies construction and allows the rafter pair to be at right angles to the roof plate & ridge.

  • This single observation explains the ground plan of reverse assembly structures.

  • It is present in LBK Longhouses, roundhouses, & larger circular buildings {Classs Ei}.[3]

  • Enables the distinction of structures such as floors from roof supports. 

  • It probably originates in PPNA as it is present at Göbekli Tepe.

2.3 Relationship between postholes & trees

A long tradition of forestry and woodland management has developed a detailed understanding of trees which can be directly related to the remains of archaeological timber structures. Through data contained in species specific yield tables.

  • DBH is diameter at breast height {4’},  is good approximation for size of the post pipe

  • The key metric is the height of crown formation {c.top height }

  • Larger trunks can be box sectioned

  • Coppice is method of growing multiple stem on single root system

  • Yield tables can form the basis of modelling

  • The general parameters of buildings and structures are in part a product of the local availability of timber .


2.4 Relationship between trees & buildings

tbc . . . . .

1. 'Excavations at the Orsett ‘Cock’ enclosure, Essex, 1976'. G. A. Carter (1998): East Anglian Archaeology Report No 86. [Illustrated by L.E. Collett]
2. Building the Past: Studies of Prehistoric Wooden Post Architecture in the Ohio Valley-Great Lakes Region, edited by Brian G. Redmond and Robert A.
3. Neolithic houses in northwest Europe and beyond, 1996, Neolithic Houses in North-West Europe and beyond (Oxbow monograph 57), T.C. Darvill , Julian Thomas (Eds).

28 April, 2021

Reversing Engineering Oxen

One Sunday, in hole under a road in Colchester, a lad on community service cautiously removed the gravelled surface of a Roman Street, to reveal a layer of yellow sand.  With great care he removed the sand to reveal a darker layer of mud with wheel ruts and the footprint of an ox. Presumably, the ox was pulling the cart from which the sand was shovelled as the first stage of surfacing the street, thereby preserving its own imprint in mud.

It is probably my favourite piece of archaeology, somehow enhanced by the circumstances. It was the earliest Roman street from the Legionary fortress which we had accessed through a hole dug through the existing road. Normally covered with a steel plate and available only when the road was closed for us on Sundays. 
This confirmation of the roman use of oxen pulling carts or wagons, [two and four wheels respectively], is not a surprise.  Scholars might ask who paid for them, who owned them, and who was responsible for maintaining the streets.  This would initiate a search of pertinent Roman historical material and finds.

However, archaeologists spend a lot of time looking at building foundations, [often unconsciously], and the presence of oxen has implications for the built environments, in particularly their use in agriculture.

Farm buildings basics
Using Oxen as a power source, principally to pull ploughs and wheeled transport, is a key component of traditional agriculture in Eurasia.  The animal's capacity for work of  effects the size of fields and farms in general, as well as the geography of the transport network more widely.  Setting aside the domestic requirements of farmers and farm workers, oxen themselves, like most components of a mixed farm require specialist buildings.
As agriculture spread North and West during the Neolithic, one cultural response to the wetter, colder and shorter growing seasons, was development of built environments.  Temperate climates made it difficult to reliably perform basic processes like drying, threshing, and winnowing crops in the open air, so specialist buildings were required.  It is this interaction of agricultural technology and practice with differing local environments and local resources, that makes "ethnography" largely irrelevant in understanding archaeology.
Farms are the commonest and most fundamental built environments; their buildings are not an optional extras or a product of later discoveries, but are the essential prerequisite for most of the culture from the Neolithic onwards.  For every Prehistoric "monument" there must be multiple farms, although this is not reflected in the literature or understanding.

  Basic Farm Buildings
  • A farm is an engineered environment of fields, tracks, buildings, water supply and other resources.  
  • The scale of farm buildings  reflects the productive potential of the agricultural unit they service. 
  • The range of building types reflects the productive potential of the agricultural unit it services.
  • Spaces may retain very specific functions, others may be multi-functional, their use varying with the season.
  • Farms are working spaces, and their design is the product on generations of ergonomic observations and best practice. 
  • Agricultural built environments closely reflect the nature of local traditions and practice.
Barns [UK]
Although the word is widely misapplied, strictly speaking a “Barn” is a building used for processing cereals.   
The two main processes being threshing, removing the grain heads from the stalks [straw], and winnowing separating the grain from chaff.  In it’s traditional form it has a central working space with bays on either side, one for unprocessed cereal and the other for the resultant straw.  The work space is often lofty reflecting the use of flails to thresh grain.  It also would have doors at both ends so that wind draught could be used to separate  [winnow] the lighter chaff from the grain.  The doors should be wide enough to facilitate access by wheeled transport.

Cereals are the staple carbohydrate for Humans and supplement the diets of domesticated animals.  Grain may require additional drying to prevent sprouting or rotting during storage.  Grains are traditionally stored in granaries, buildings characterised by raised floors and good ventilation.  The local tradition [N England] is to site granaries over the cart shed.
Cart Shed
Wooden carts [2 wheels] and waggons [4 wheels] require special buildings  to preserve them when not in use.  They are associated with a variety of harness and other tackle made from leather and other materials that equally need protection from the elements.  More generally, farms have a Varity of of specialist tools and equipment that will require storage space in building preferably situated close to where they will be used.

Ox / Cow House
Working oxen need a building to house them with provision for water, feed and bedding.  Such buildings usually low ceiling sometimes with slightly wider door.
The oxen are houses in individual stalls, or in exceptional circumstances loose boxes, which are provided with permanent troughs and mangers.  The stalls have bedding of straw to absorb urine and facies, which has to be "mucked out" regularly which in turn requires a muck heap or midden where such organic material is stored.

Other Oxen Engineering Issues
If you use wagons, their width and turning circle has to be reflected in the ergonomics of the working spaces and wider infrastructure.
If used to pull wagons on metalled roads, the Oxen may require shoeing.  Unlike horses, oxen cannot stand on 3 legs, thus, require to be fully supported and restrained while being shod, requiring an engineering solution with foundations, and therefore archaeology.
There is a tenancy in archaeological practice to see excavation data in terms of what has been fund before, introducing both circularity and selection bias.  Thus, thinking about the archaeology of built environments has not extended beyond the simplistic and fundamentally racist tropes about primitive huts for primitive peoples derived from the sort of ideas about cultural evolution that drove national socialism.  Thus, the engineering required to shoe an ox, or its turning circle is seldom considered by an academic culture steeped in a colonial view of our primitive ancestors and their beliefs.

As Theoretical Structural Archaeology is about understanding archaeological buildings and structures I was naturally intrigued by recent set of Roman structures uncovered near Scarborough.   My initial reaction, [which invariably proves to be wrong], was it was a signal tower, however, having seen more detailed footage, I would postulate a different interpretation.

The well built structure could be a specialist barn, with an animal powered threshing floor [or mill], something similar to buildings locally known as a gin gang.  The addition of floored granary at the rear of the building completes picture. 
In this particular case, I would expect a central archaeological feature representing the spindle of the system in the centre of a threshing or milling area.  In addition, I might just expect wooden floors or hard flooring in the ancillary crop storage buildings, but apart from basic render, I would not expect wall plaster, tesserae, or other high status domestic fixtures and fittings.        

14 April, 2021

Who Shot British Prehistory in the Head?

If Academic Archaeology has become a bastion of science denial, who is to blame?

I realised British Archaeology was unwell, when I attended TAG 90, where the psychosis was already becoming evident. The Theoretical Archaeology Group, ;[or theoretical archaeologist group as I would characterise a group of academics temperamentally unsuited to practice archaeology, and for whom knowledge is not constrained by evidence or the English Language]; was a stepping stone for many who have subsequently helped fabricate the mindless melange of the New Post-rational Archaeology.

When, in 2006, I started my Ph.D. at Newcastle, a University so awful that even the staff had walked out, a small detail curiously omitted from their website, I had little idea how prevalent Science Denial had become. Not only was my engineering science of no interest, I was told to write about how buildings were perceived; in the Iron Age. While being ejected from a building bequeathed to the University by one of most region’s most famous engineering families, I had for a fleeting moment imagined that this bottom feeder of the academic system was just a venally corrupt nadir of mediocracy; but no, it's about par for the course.

Archaeology is an easy subject to dumb down, helping the University achieve the expected return on it’s property portfolio. Students are churned in their hundreds to find the next generation of credulous youth to maintain the tradition of copying out other peoples work in your best handwriting to obtain "research" funding.

What you learn at University is how to be a lecturer.  As a result, the standards in archaeology, as it descends further into mere infotainment, are scandalously poor on many levels, with publicly funded institutions routinely promoting science denial, myth and faith based archaeology.

For me, an essential prerequisite of a Theory is a dataset; but, given their monopoly, many academics have dispensed with the need for evidence and even the constrains of the English Language to revel in tautological self-indulgence and linguistic prestidigitation designed to conceal the nature of their conceits from those students & colleagues easily intimidated by a few polysyllables.

Let's Blame the BBC

However, I finally realised British academic archaeology was brain dead, when I chanced upon A History of Ancient Britain Series 1 Episode 3 Age of Cosmology. Even the title only makes sense if we completely redefine the Words "History" and "Cosmology" to mean the exact opposite of what they used to mean.

This is knowledge that is neither based on, or limited by, fact or meaningful language.  So I leave you in the capable hands of embryonic national treasure Dr Neil Oliver, as he and the BBC redefine the concepts of History, Cosmology, The Neolithic Revolution and intelligent thought, all in about 60 seconds.

13 April, 2021

The “Turf“ Wall; Science Denial at English Heritage / Historic England – Now It’s Official

To test the water, and offer English Heritage a chance to consider the matter I sent an e-mail explaining the Science that proves Bede, writing in the C8th was wrong to suggest Hadrian built a Wall of turf aka The Turf Wall.

Twenty years ago their own excavation Appleby produced unequivocal evidence that this section of Wall was made of Timber, information they failed to comprehend at the time.[1]

The science is simple and irrefutable.

1. Soil science.
If turf is blocks of local soil held together with plant roots, then the composition of the "Turf " Wall deposit at Appletree with its complete absence of mechanical particles other than some sand grains in what is essentially a peaty deposit indicates that this cannot have derived from a local soil and therefore, can not ever been made of Turves.
[QED] [2]

2. Palynology
The palynology dominated by tree species alder, oak and in particular Hazel, [ a shrub] [3]
3. Palaeobotany
The recovered plant macrofossils were dominated by pieces of carbonised wood, trunk & branch up 0.01m, and notable remains of Ceratodon purpureus fruiting bodies. [4]


4. All the scientific evidence, indicate the use of timber to construct this rampart, a conclusion which is also confirmed by the Roman’s own accounts of their engineering.[5]
5. It is fair to conclude that the concept of a “Turf Wall” is a native literary tradition, now largely driven by nominative determinism, and the momentum of the inherited orthodoxy in institutions.

I sent an email outlining the arguments using their data [6]


I am a structural archaeologist working in the NE of England and I have serious concerns about the denial of Science in favour of faith-based arguments.

20 years ago you produced a report that proved beyond all doubt that the Romans did not build a "Turf" Wall using soil science palynology and palaeobotany; tragically, the report concluded the exact opposite.

This prompts serious questions about quality control and competence at the highest level.

Thus, my principle question is who takes responsibility for such serious mistakes and the blatant denial of science that ideas like a "Turf Wall" represent?

Is anyone at EH prepared to defend this non-scientific stance in public or discuss the issues it raises?


Geoff Carter

After the usual robotic exchange of pleasantries, they responded thusly.

Dear Geoff,

Thank you for your email. It is always interesting to hear alternative interpretations. However, it remains our view based on the evidence recovered from a number of excavations and associated analyses that the wall is constructed of turves in the widest sense with Appletree as the classic example.

A consideration of turves in the archaeological record is laid out in Hall, A R 2003 Recognition and Characterisation of Turves in Archaeological Occupation Deposits by means of Macrofossil Plant Remains. Historic England Research Report 16/2003.

Kind regards,

Rosie Ryder

Historic England Communications Team

I responded, seeking reassurance they had understood the argument, and further pressing my point, but no further communication was forthcoming.[8]

" . the wall is constructed of turves in the widest sense with Appletree . . " is basically a denial of the science, with not enough wiggle room to escape such a charge. 


  • While as an academic subject, “Research“ is driven by simple reproduction of the existing narrative, since the skills necessary to understand archaeological base-data are often lacking.
  • The reference cited reviews the evidence of “turf” in a variety of contexts, and demonstrated that archaeological expectations are not by and large confirmed by paleoenvironmental data
  • It highlights a broader lack of basic methodology and the tendency to use of excavations as an opportunity to reinforce or fine tune part of an existing narrative, ignoring or excluding data that does not fit the expected pattern.
  • However, even learning Archaeology out of a book from someone who learned it out of a book, should not preclude a basic understanding of soil science, it is after all, what archaeologists find most of.
  • Institutions, working in monopoly, offering careers for life, and in an environment where their customers, students and the public can be assumed to be wrong, have no market pressures to raise their game above a minimalistic mediocracy.
  • Archaeology is not mission critical, nobody dies through this sort of science denial, and while disappointing, it’s only our money and their institutional creditability that is being wasting.


[1] Hadrian’s Wall Archaeological Research by English Heritage 1976–2000

edited by Tony Wilmott
http://archaeologydataservice.ac.uk/archiveDS/archiveDownload?t=arch-1416-1/dissemination/pdf/9781848021587_all.pdf [Accessed 25/12/2014],

[2] op. cit.116 The plant macrofossils,  Allan Hall

[3]op cit p. 114 the pollen  James Wells

[4]Ceratodon purpureus, Fire Moss,  present in quantity, which as the name suggests is an early coloniser after forest fires, and it commonly grows on is dead wood.

[5] a. C. Julius Caesar, Gallic War 
http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.02.0001  [Accessed 25/12/2014],
b. C. Julius Caesar, Commentaries on the Civil War  William Duncan, Ed.
http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.02.0076 [Accessed 25/12/2014],
c.  The Military Institutions of the Romans (De Re Militari) by Flavius Vegetius Renatus, Translated from the Latin by Lieutenant John Clarke, translation published in 1767.   Etext version by Mads Brevik (2001)
http://www.digitalattic.org/home/war/vegetius/  [Accessed 25/12/2014],
d. Polybius, Histories http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.01.0234 [Accessed 25/12/2014],[7] 12 Feb, 09:51
[6] Dear Rosie,
Thank you for your prompt reply and the link; this is a very important paper as it it demonstrates my view that the “evidence” is not scientific, but is driven by archaeologists’ expectations.  
It confirms that from the plant micro-fossil point of view the case is not proven in any Roman context, and draws attentions to other, more normal processes that can account for these assemblages.  [The occasional use of turf as a roofing material and even for small walls in area devoid of other resources is not in dispute].
Deposits derived from crop processing, organic flooring such as reeds, charcoal burning,
and the decay of building materials such as daub are theoretical sources of plant assemblages, that might be similar to turves.
The issue of soil science, in particular the lack of mineral particles in “Peaty” deposits is not discussed; it is one of the deeper issues with archaeological fieldwork being driven by the existing literature.  
I have observed that archaeologists when dealing with soil have a culture of “stick in a bag and ask the specialists what it means”.   To which the hard-pressed specialist has asked for a specific question about a specific context.  The science is being asked the wrong questions; rather than, where did the turves come from?
It should be what is the origin of this deposit?
It is partly a tradition of the way archaeology funding is granted in terms of objectives, project design and “Answering Questions”.
In short, there is nothing in the evidence presented that demonstrates the use of turf in Roman Military contexts, and I would argue that the plant micro-fossil evidence that has been retrieved confirms the use of timber.
Further, the soils at Appletree make it impossible; that is not an opinion, it is archaeological soil science 101.*
I will look at the data tables in more detail, particularly the mosses, but you do not have any “Science” on your side, only a literary tradition dating back to Bede.
Naturally, it is a matter I intend to push you on, can you take this matter any further?
* Being an archaeologist is much more difficult than people imagine, especially if you have actually been trained as an archaeological lecturer by an a university lecturer with no real experience of being an archaeologist or writing up complex excavations.
Geoff Carter
Structural Archaeologist

12 April, 2021

How The Roman Army Bridged The North Tyne At Chesters

How to build a mortared structure in a stony river bed 
1. Dig a diversion Channel
2 Dam the river at both ends & Divert the river
3 Constructed mortared stone peers in river bed
4 Construct bridge
5 Remove Dams
6 Block diversion channel


  • 1 The initial Bridge was intended to carry the Wall only.
  • 2 In theory, second [undetected] Bridge would have carried the Road south of the Wall. this road is evidenced by its construction trench aka The Vallum.
  • 3 [This itself was have replaced another lost bridge for the Staingate road, although piled timber would be adequate for road bridges].  
  • 4 This first phase of road, like most of the early “Broad Wall”  was never completed
  • 5 Subsequently, a second wider bridge was constructed to carry the Wall & a roadway now represented by the Military Way towards the end of the century.

The Diversion Channel encloses an area almost a large as the fort at Chesters on the opposite bank, one of the original forts presumably designed by Hadrian, who would have almost certainly got involved with bridge design.

Standard Disclaimer; Not Available at University

Academics just don’t think about these problems, and are content with reproducing of the ideas previous generations. Thus, as an evidence based form of archaeology using science and engineering  proved incompatible with the faith based archaeology currently practiced at many Russell Brand Universities like Newcastle, the last bastions of Science denial.

26 March, 2021

A Momentary Digression & New Blog

 Found Down The Back of a Digital Sofa.            Just to avoid confusion and to let off steam under the pressure of lock down I have created a new blog as repository for Non Archaeological satire, art, cartoons and photography.

It is called: Found down the back of a Digital Sofa, and represents a few persistent stains on the fabric of time that have proved difficult to remove.   The sort of thing found in my twitter feed. 

When you work is not good enough for sector of Higher Education increasing reliant on Science denial and academics purporting the views and perception of our ancient  dead - you are driven to a satirical view of the world.   

The current post concerns a traditional North East Digital Arts Festival of Vegetable Baiting, thus, given the obscurity and specialist nature of my subject matter, the constant need to contextualise and explain the jokes or humour rather precludes its designation as the latter; similarly, some passing familiarity with the subject matter might be considered a not unreasonable prerequisite for satire; you have been warned.

This is all undoubtedly of no interest and represents the dark side of a warren of rabbit holes so obscure that no reasonable man could be expected to believe that any of it was real.

22 February, 2021

Reverse Engineering Roman Cavalry

1. Context.

In the precious post I was quite hard, if not downright disrespectful about some of strange conceptions about how cavalry horses might be stabled. So it’s time to put some cards on the table, and explain how horses and built environments are meant to interact – from a more traditional perspective, after all, cavalry barracks have existed and continue to exist since ancient times, and horse care in a variety of contexts is hardly a forgotten art.

My work for Philip Crummy in Colchester on Britain's first legionary fortress taught me to respect the accuracy of Roman Military surveyors. An important point also was apparent; Romans favoured stone foundations, but significant parts of the superstructure were built from timber for ease and speed of construction.  In terms of Hadrian’s Wall, we have very poor data sets, but the Roman army was very systematic in its architecture, so the Fort chosen is North of the Wall at Birrens in South West Scotland.

Theoretical modelling is a way of testing and refining ideas about how buildings and built environment might work. In this context, given the number of unknowns, modelling can only give you a range of answers and help delineate the problem. Having tried out various options against the available data, what is presented is a best fit model, directed to a specific aspect of a problem, in this case how many horses can you house in a cavalry stable, and what does this tell us about the size of cavalry units.

There is certain fetish about deploying Latin vocabulary which is not always helpful, however, I have to confess a prejudice to the use of Cohort sized units [600] and centuries [100]. There are a variety of terms deployed notably, equase, decurion, turma, ala, quingenaria, and Milliaria.  While the primary objective is to develop a model of a cavalry barrack, and from this delaminate the scale of units, relating this to Latin vocabulary would be seen as an academic objective

2. Roman Forts Basics

It is generally understood that the layout of camps mirrors the layout of the Roman marching camp, which in turn reflects the structure of the army, with individual 8 men tents [contubernium] formed up in centuries, and cohorts. The disposition of cavalry may reflect picket lines of horses, which have to laid out with same aims in mind, namely keeping them securely organised for ease of care, deployment and preventing them from kicking each other.  

In the Roman Army class is important in the distribution of Space, notable for the space allocated to the Roman commanders house & bathing. Forts are similar in plan being built up from the similar components, principally, a single Headquarters building, Commanders house [+bath], Hospital, and  varied numbers of; Infantry barracks, Workshops / Stores , Granaries, and Stables. 

 3. Hadrian's Wall & Birrens

This exercise is try get a sense of Hadrian’s design for his Wall in terms of cavalry, principally because they represent be an ideal supervised the emperor, which is a great context for archaeology. In reality, the evidence from this Broad Wall phase is fragmentary, and most of the forts were built or rebuilt after the initial phase. The best preserved cavalry fort in the North is at Birrens, part of the Antonine Frontier built after Hadrian’s Wall was initially abandoned.

Much of the Plan was recovered, but has a few problems, particularly the lack of a commanders house, some ambiguity about building A2, and a sense that the fort is a bit light on storage / workshops. There is an annex to the East which probably accounts for this. The site appears to have been tarted up at some stage with rebuilding or refacing the gable ends of buildings.

 4. Cavalry; Human Consideration & assumptions

As I understand it, in this period Auxiliary Cavalrymen were high status non-Roman troops from horse owning elites elsewhere in the empire. It is not known whether the status of cavalry was reflected in their accommodation. They were an expensive resource intensive asset, and presumably would be equipped the best horses available in the area where the unit was raised.

My guess / assumption is that there is a 1:1 ratio of support troops to cavalry troopers. Apart from Historical best practice; the following considerations may apply:

  • Need to deploy the whole unit en masse and quickly.
  • Armoured men with weapons are not suited to the preparation or care of horses.
  • Cavalry extends fort’s curtain wall which requires additional troops to defend.
Cavalry have to be part of a predominantly infantry unit.

5. Horses General Consideration & assumption

Keeping large numbers of horses undercover in a compact area on a long term basis requires a specially adapted built environment. Horses prefer high airy spaces, with underlying floor surfaces that are dry, firm, but not too hard, and graded for drainage.


A building with access to water supply and suitably drained, with individual Space for each horse, allowing for; Feeding, Watering, Mucking Out, Grooming and Tacking up.

  • Storage for tack and other kit.
  • Wider and taller entrances. 
  • Space for mounting and forming up.

Other buildings;

  • Sheds or lofts for Forage / Hay / Bedding
  • Granaries for Barley & Oats
  • Buildings for: Blacksmith / Farrier; Equine vet; Sadler
  • Ideally, a covered space for training, assembly and practice.  

 6. General model; The Roman fort at Birrens

The model includes a consideration the whole fort as a context for the cavalry stables.

 The fort is regularly laid out in Roman feet shown at @0.296m; however, it is not necessary to best guess precisely what is going on in the minds of the surveyors and builders, for the following reasons:

  • I do not wish to push the accuracy planning historical and modern.
  • Precisely what is being measured, including the thickness of the component is not clear.
  • The dataset is for the measurements of foundations not roofs
  • Allocation of external spaces like roadways is not implicit in the design of individual buildings
  • It is only relevant to the number of bays in the stables and their capacity. 
Looked at as a whole the fort is a nominal 600 x 400 ' centred on the HQ building, each set of stables occupies a plot about 150' square, roughly the same as the 6 double infantry blocks.
Including Granaries G3 & G4, and  building A3, the stables account for 40% of the forts area.

The use of standard measurements and components greatly simplifies construction and is evidenced by the uniformity of the building types. The use of standard roof trusses, which in turn is reflected in standard bays, is most clear on the buttressed buildings.

The 150’ long barracks are presumably about 10 – 12 bays long, [11 being not uncommon on the Wall]. Some produced evidence for partitions, perhaps at 60, 120, feet, while others produced no evidence. It cannot be cannot presumed there is only one type of barrack represented.

The end on nature of the Stables allows them to be packed closer together than side on buildings like the barracks. Double Walled barracks show the dedication to the single truss and the avoidance of valleys. Built back to back they can make use of the terraced sloping sites to improve drainage.

It is worth noting that between Granary G1 and building A1 there appears to be a corn dryer, which suggest that crop processing is taking place.  In which case A1 may be a barn for processing and storage of harvested grain, indicating some degree of local arable production by the garrison.  For a cavalry fort the need for meadow and grazing, and more specialised grains implies a more complex agricultural hinterland.

7.  Roman Stable theoretical model

Based on the buildings at Birrens, the model has two sets of stalls with a central passage, and serviced by feeding passages. There is a loft for hay or bedding overhead.

The capacity of buildings are dependent

  • The choice of bay size
  • The number of occupied bays.
  • The number of horses per bay

The model assumes 4 horses per bay, utilising 10 - 13 bays per building as shown in the table below. [2]  The buildings are 150’ long; allow for the thickness of partitions, 10 – 12 bays at 15 – 12.5 foot intervals work well, which offers a range of values for the number of horses of 30 – 50.

Once the models covered central passage is accepted, it is simply a matter of how many horses can fit on the two rows to either side. In this respect a five foot stall is probably too narrow, and 6 foot stall generous. Assumptions also have to be made about the provision for spare horses and even whether officers had more stable space.

8]. Conclusions

Within the parameters set out the model stable has a capacity between 30 – 50 horses or 180 – 300 horses for the whole fort / unit. Offering three probable scenarios for the six buildings 

  • A]. 2 x 100 man units
  • B]. 3 x 100 man units
  • C]. 2 or 3 x units of intermediate strength. 

Solution A; 200 horses

Each stable would hold the horses of a troupe of 30 + 3 officers, a century being 3 such troupes; 90 troopers + officers.  The six blocks are a nominal 200 horses for 200 cavalry men. 

Two units fits with the 2 Extra Granaries for feed,{G3/4} each with six bays, which together the 2 Cohort Granaries, {G1/2} and the axial symmetry of the fort layout, all suggesting we are have two units. 

At Birrens there is potentially 16 spaces, representing a surfeit of potential infantry barracks with room for 1200 in the 6 double blocks alone, with another 4 blocks spare; two are in prime position next the central area with access from both sides.  Various combinations seem possible, based on 2 cohorts +/- cavalry.

One way of accounting for this space is to assume the cavalry have more generous quarters, perhaps  3 blocks per unit mirroring the layout of the stables.  Giving 6 blocks for cavalrymen, 2 for support troops, and 6 for an infantry cohort, making 14 units in total.   Thus, detailed understanding of the garrison is dependent on assumptions about the ratio of horses to cavalrymen and support troops, as well as how their status might be reflected in the allocation of living space.

The minimum view is that we have two centuries, comprising 200 horses, with 200 cavalrymen & 200 support troops.  With the addition of an infantry Cohort of 600 this would create a garrison / unit size of 1000.

Solution B 300 horses & Solution C 200 -300 horses.

To get 50 or more horses per stable would require narrow stalls and leave little options for spare horses.  It seems too much of a push to get to 300 horses comfortably onto the site.  However, within the modelling it is possible to conceive of an understrength 300 man unit.

Thus, all the above does not preclude a unit comprising any vaguely sensible number between 200 – 300; a unit of 240 horse could be 3 units of 80 would fit, and make supporters of the 80 man century very happy.  

After Inscription from Birrens  dedicated by II cohort of Tungrians {Rib I 2110} [3]

The modelling pushes an engineering perspective, which has its own logic and drive for uniformity, which in the context of the Roman Army is not inappropriate.  Notwithstanding the issues of  how cavalrymen were accommodated, the ratio of support troops and infantry to horses, the model helps delimit the scale of cavalry units, particularly emphasising the space required compared with regular infantry units.
Happily, historically it is thought that the fort was occupied by II cohort of Tungrians a 1000 strong unit mixed unit.


 [1] Traditionally, the front ranks of a nominal army line is formed from the younger fitter soldiers, with the more senior and more experienced towards the back.  Support troops are the more senior soldiers who are not as physically fit, but are highly trained and well motivated. They represent the specialist in medicine, leather work, armourers and administrators, who do not routinely leave the fort; on campaign they travel with the baggage.  The eight men leather tents which each unit used, formed the basis of the layout of the camp, but would require a mule to carry, and a second to carry the collective equipment of the unit. The baggage is the most valuable part of the army group in the field

[2] The table below is based on the following

  1. .Bay width / stall width in Roman foot of 0.296m
  2.  Stall is the Stall width – 0.5‘
  3.  Assumes 4 horses per bay
  4.  Assumes two bays not in use or spare

[3] For the Emperor Caesar Titus Aelius Hadrianus Antoninus Augustus Pius, pontifex maximus, in the twenty-first year of tribunician power, four times consul, the Second Cohort of Tungrians, a thousand strong, part-mounted, publicly praised, (set this up) under Julius Verus, emperor’s propraetorian legate.