Owstons Warehouse, investigation of south east corner of building and quay.

The emplacement of access scaffolding around the lower south east corner of Owstons Warehouse and

quay has allowed close examination of the wall for the first time.

Access to the quay from this end was obstructed by a short wall perpendicular to the south elevation of

the building, originally in line with the east wall but which had moved away. The ground level to the east

– and particularly at the corner – is lower than the quay and falls away steeply toward the river.

The brickwork of the building quoin immediately above the top of this short wall was missing or

disrupted to a height of 109” above quay level. The wall itself undercut this quoin and has moved away

from this undercutting, suggesting that it had been built as a buttress against earlier decay.

Upon the quay, within this wall, there are significant sycamore and ivy stumps, recently cut back, and

these roots may be assumed to have contributed to the disruption of this buttressing wall, as well,

perhaps, to the disruption of the building corner as a whole.

However, necessary dismantlement of this deflected wall leads to another analysis.

The wall is almost certainly contemporary with the construction of the warehouse. Its return is angled

similarly to the building and was built of the same ‘special’ bricks required to all quoins of the building

due to the lack of squareness of the site.

The brickwork rose from a large block of calcareous sandstone, the thickness and length of the wall, as

well as carved to form the same angle. This slab of stone, some 7” high is contiguous with the stones

that form the top of the quay wall and of the same geology. Significantly it also formed part of the

return of the east elevation, deliberately undercutting the quoin – three courses of brickwork abut its

north end and were clearly built against it. The junction of the brickwork of the building and of the wall

is more ragged, but this is due to the fracturing of contiguous brickwork – the wall was never butted up

against an already constructed quoin, it was part of this quoin and an extension to its full height of the

east wall.

This height may have originally been almost to the level to which quoin stones have been assumed to

have fallen away. This is also the height at which there is a channel, cut, or even ‘built’, into the south

wall, and this channel may mark the original maximum height of this wall, though its purpose remains

unexplained

The 1850 Ordnance Survey Map, which is very accurate, shows the quay diminishing in width at the east

end (which it does), but also a solid ‘step’ at the east end significantly wider than the wall – this suggests

that the wall and channel in the south wall held a flat roof in the past, a shelter perhaps.

The ragged corner of the building here is the result of decay and separation of this formerly attached

wall, therefore, and not evidence of collapse.

Although as yet unexcavated below the level of the large stone, this latter has been slid aside, revealing

another large foundation stone partly beneath the corner and a view of a further such stone beneath

the east wall to the north. The quoin of the quay beneath the wall has been repaired with bricks in

ordinary Portland cement mortar. It may be assumed that this replaces a decayed or dislodged stone

quoin and is a relatively recent shoring repair. A similarly cement bound section of brickwork abutted

the wall to the west. Leverage of the expanding sycamore tree against this cemented brickwork, which

has in turn been forced into the base of the original wall, may explain the deflection of the latter, which

had been shunted eastwards.

It remains the case, however, that removal of the tree and ivy stumps and root balls has the potential to

destabilise the corner of the building. This must be further assessed prior to a final method statement

being formed.

The corner is currently more stable than it appears, however. Most of the loss is from the end of the

thickness of the east wall, not from the face of the south.

The plan before full investigation had been to quit this section of wall, which was assumed to be an

improvised addition, and to rebuild the corner.

Some repair and consolidation of the corner will, of course, be necessary, but it would now seem

unjustified not to reinstate the wall, using as much of its original material as possible, and to tie it once

more to the east wall.

It will first be necessary to dismantle the wall to a sound footing, removing all cemented brickwork. This

will be done in association with the removal of all tree stumps and roots. The quay wall to the riverside

is infested with substantial sycamore trees, some 5 in total. Their removal will entail the careful

dismantlement of the upper corner of the quay and the excavation to some depth of the quayside itself

in this area. Roots seem to have penetrated the building below the ground level of the quay and these,

too will need to be removed, followed by consolidation of the foundation. In prudence, the corner of the

building will need to be braced against potential – if perhaps unlikely – collapse during these remedial

works.

It should be noted in this context that the partial dismantlement of the wall beneath the easternmost

window of the south elevation – to facilitate the introduction of ladder beams connecting to the internal

birdcage scaffolding, and the suspension of a scaffold over the quay-edge – has revealed the

construction of the plinth level of the building hereabouts.

The wall is a composite of brick and calcareous sandstone, but is unusual, to say the least and strongly

supports the notion that Owstons Warehouse is built upon and incorporates to some extent the earlier

Navigation building on this site, built in 1725.

The brick wall is formed around sandstone blocks of variable depth – the stones are encased inside and

out with brickwork. This is not a normal pattern of construction. The blocks are of dressed ashlar,

although this is weathered.

If this is indeed part of the earlier building, it would support the theory that the quay itself is older than

Owstons Warehouse, and is of 1725 construction. It would be likely, therefore, that the foundation of

Owstons and the quay itself were built at the same time, and that the stone footing of the warehouse

exposed by excavation beneath the brick plinth inside the building is older than the brickwork above.

terrier map 1730

1728

NC 28.05.2009

Removal of the brick repair to the corner revealed a large calcareous sandstone block returning

westwards and beneath the root ball of the sycamore. This forms the quay edge. This stone is minimally

deflected and would be a sound base from which to rebuild (subject to inspection of the quay wall

beneath). The horizontal jacking from the tree and ivy roots has not affected this stone, but the brick

and stone work above it only.

The tree and ivy roots are extensive above and behind this quay-stone, however and the extent to which

they have penetrated the building is as yet unknown.

The plinth level of the south facade behind the sycamore trunk is of stone.

The tree trunk and roots will now be carefully reduced and removed.

NC 29.05.09

Owstons quayside.

The condition of the eastern end of the quay, largely masked from view by branches of a sycamore tree

growing from the quay wall is of more concern than originally thought.

The deflected brick wall at the east end of the quay having been dismantled and scaffolding suspended

over the quay wall, smaller branches have been sawn off to allow a closer inspection of the wall itself.

What had appeared from above as three separate trees is, in fact, just one, which has grown out of the

quay and expanded horizontally as well as vertically. The ‘trunk’ mass measures some 3 metres long by 1

metre high; it has wrapped itself around the stones at the top of the quay and its roots have penetrated

and expanded in the joints of the stonework at the upper level of the wall beyond the trunk mass.

The east corner of the quay wall has been prised apart by the roots of this sycamore, as well as by those

of another, growing against the south wall of the building and by significant ivy roots that have wrapped

themselves around the quoin stones.

The quoin comprises large, heavy calcareous sandstone blocks. It will be necessary to dismantle this

quoin during the removal of the roots of these trees and to rebuild it immediately afterwards.

Removal of the major tree roots will be difficult and problematic. They have melded to some extent with

the ashlar blocks and the quay-side copings. Removal of one will risk removal of all. Breaking of the

roots of the largest tree on the quay top may lead to the extensive horizontal trunk and the stones it has

absorbed falling in a less than controlled manner.

The scaffold currently allowing access and inspection is suspended over the river, which is at least 7 feet

deep at this point – it is questionable whether such a suspended scaffold will be up to safely bearing the

weight of the quoin stones and may be called upon to carry a significant load during the removal of the

tree trunk and subsequent repair of the wall. It will be necessary to hoist the quoin stones up and away

initially in order to avoid loading of the scaffold.

Owstons Warehouse Quayside, supplementary notes

As detailed upon the 1850 Ordnance Survey map, the riverbank steps in to the east of Owstons

Warehouse and its quay. A little further to the east, there is a flight of steps giving riverside loading and

unloading access to another building which at this time would seem to have been in distinct ownership

or tenancy to Owstons itself. The building that was served by these steps has now gone.

Clearance of overhanging ivy to the east of Owstons has allowed some inspection of this area which is

currently some four feet below the level of the yard to the north of Owstons, below a concrete block

wall which abuts the east elevation of the warehouse at its mid-way point.

The opening for the steps survives. It has been infilled in the past, apparently with soil and this has

spilled somewhat into the river. Between Owstons quay and the opening for these steps, the wall is of

typically C19 brickwork, laid or at least pointed with a pale cementitious mortar. The same mortar

appears to have been used to carry out patch repairs and some little repointing to the stonework of

Owstons quay also and at the same time, perhaps. This may be of some age. The bricks that form the

quoin at the entrance to the steps are half-rounded. This brickwork, as well as the use of half-rounded

quoin-bricks is similar to the brickwork inserted beneath the north arch of the dry-dock at the other end

of Owstons and may well have been executed at the same time, towards the end of the C19 or during

the earliest years of the C20. It is likely to be a refacing or replacement of a stone wall, the lower courses

and footing of which are currently visible above the water-line. The brick retaining wall is topped by

large calcareous sandstone blocks similar to those upon Owstons quay wall, indicating that this area was

also a quay, probably after the upstream extension of the Navigation after 1810. The wide joint between

bricks and quay edge stones is due to the slight subsidence of the backs of these probably deep stones,

not subsidence of the brickwork itself. There has been a significant accumulation of debris and soil and

composted vegetation, as well as of tree and ivy roots above this wall – up to 1 metre higher than

originally.

There is a sizable sycamore tree growing in the infill material of the steps. The probably stone steps

themselves may be expected to remain in situ beneath the infill material.

The eastern quoin of the steps opening is formed of roughly 12” high blocks of calcareous sandstone.

Like the wall itself, these are in a generally sound condition. This wall also is topped with large edging

stones consistent with this area having served as another quay alongside that of Owstons and at a

somewhat lower level.

If ground levels to the north and east of Owstons Warehouse are returned to their earlier location, the

concrete wall above this easterly quay area would be removed. The stone quayside and steps here, too,

might be readily regained.

NC 02.06.09

Owstons Dry-dock survey.

Removal of scaffold-boards in place since the beginning of the job, as well as the low summer levels of

the river and the clearance of vegetation, have allowed a close inspection of the dry-dock area for the

first time. It is in variable condition.

In places, there has been extensive delamination of the calcareous sandstone ashlar blocks of which the

lower walls of the dry-dock area are constructed. In places, particularly to the riverside returns of the

wall to either side of the steps, blocks have simply fallen away, leaving other blocks cantilevering above

them. In places, tree roots from large sycamore trees above and on the edge of the former quays to

either side have lifted and partially enveloped whole stones as well as pushing out stones below.

Delamination and crumbling, east of west wall

within dry-dock

Tree roots and trunk at top of this section

West of east wall inside dry-dock – essentially sound,

needing repointing only; upper two stones of quoin being

forced sideways by tree roots.

However, the overall condition of the quay walls is remarkably good, given their almost certain

construction around 1725.

Logistically, the repair of these sections of wall will be problematic.

riverside return of quay, west side; note mortared limestone wall

core

Calcareous sandstone is currently unavailable and any other available sandstone would be unsuitable.

There are three separate but contiguous quays in this area of similar character and construction.

Owston’s quay and that to the west of Owstons were almost certainly built at the same time; the one to

the east may be somewhat later. The buildings with which the quays to either side were associated have

been lost, as has the earlier building that Owston’s Warehouse itself displaced.

The walls of all three quays are an important historic, but also a major structural element of the

riverbank at this point. The loss of integrity or the collapse of the quay walls to one or other side of the

Warehouse would have potentially serious consequences for the long-term stability of Owstons

Warehouse itself.

Every effort must be made, therefore, to repair these historically and structurally significant structures.

In places where stones have simply fallen out, some of these stones may be retrieved, even from the

river itself, for reinstatement. In places where severe delamination or structural failure of individual

stones has occurred, these areas may be repaired with calcareous sandstone tile laid in a robust NHL

lime mortar. In the absence of available new stone of similar geology, and given the gently eroded

condition of the original ashlar blocks, tile repair would represent a suitable and relatively unobtrusive

method of repair. It would allow the maximum retention of historic fabric, delineate original material

from repair and avoid the wholesale removal of heavily eroded ashlar blocks of unpredictable depth the

removal of which might disrupt stones above. All roots and tree trunks must be removed and quay

stones that they have disrupted be reset.

Where the facing has been lost beyond the west quoin of the dry-dock, the internal structure of the

quay walls is visible. This will almost certainly be the same as the internal structure of Owston’s

Warehouse quay itself: the large calcareous sandstone ashlar blocks face up a secondary ‘wall’ and core

of carefully laid limestone rubble, its units also of significant dimension and lime mortared. This explains

the general stability and good condition of the quays in this area which have only been disrupted by the

intrusion, jacking and leverage of significant tree-roots.

mouth of drain

structure of drain: stone ashlar

at wall-face; brick lining; stone

slab top.

Note intrusion of tree-roots

There is a formed drain from the rainwater goods of Owston’s west end which exits through the quay

wall via a carved stone. The drain is brick-built.

In the dry-dock area, at least, the logical sequence of works will be to complete repair and consolidation

at the lower levels before tackling the removal of tree roots above and the resetting of disrupted quay

edge stones. Lime should be French NHL 3.5.

Nigel Copsey 08.07.2009.

Removal of the tree root proved to be arduous and time-consuming.

Dismantlement of the disrupted corner of the quay made clear that this corner had been rebuilt once

before – much of the stone of its construction at the higher and disrupted level was not local calcareous,

but North York Moors sandstone. The brick wall at this corner must also have been rebuilt in the past,

therefore.

Indeed, the lime mortar within the brick wall and the rebuild was found to be uncommonly hard; the

mortar of construction of the original quay (when this was reached) of a much more typical strength.

The tree root had penetrated to the full depth of this earlier reconstruction.

It was clear that the core of the quay had not been built as solidly, or as diligently as the original. The

consequent looseness of the core, therefore, gave the tree roots more opportunity to penetrate

vertically through the core. As detailed above, the core of the original 1725 build was of oolitic

limestone fully surrounded by lime mortar, presenting significant resistance not only to catastrophic

water penetration, but also to tree roots.

Further along the quay, where another large tree trunk remains, the wall is disrupted, stones have been

lost into the river, but the core is solid, the root penetration vertically less severe, it is to be hoped.

Where no trees had been allowed to take hold, the quay wall is essentially sound, requiring only

repointing and some tile and mortar repair.

Repair of the east end of the quay proceeded upon removal of all but the vestiges of the tree root; the

urgency of this repair informed by concern that the river levels beginning to rise at this time of year

would either prevent consolidation of the quay or worse, in flood. Wash out the footing of the

warehouse.

Original calcareous sandstone and jurassic sandstone blocks from the earlier repair were reused and

coursing was matched to the original coursing pattern of the quay. Some of the latter blocks had been

higher than the originals, disrupting the coursing and reducing the bond of the repair with the original

wall. These stones were dressed down to avoid this and to achieve maximum attachment between the

original material and the current repair. Heavily eroded original stones were turned where necessary to

utilise a better available face. New stones were also used – four blocks of Woodkirk sandstone and

others from the North York Moors, newly quarried. All new stones were tooled as per histroic local

practice and by reference to small survivng examples of original tooling on the quay.

The core of the wall was built up behind each course in turn, of well-mortared limestone and sandstone

rubble. This was extended into any voids within the footing of the warehouse.

Three new coping stones will be required. These will be of Aislaby sandstone. The original quay copings

are of local calcareous sandstone.

Mortar was 2 parts (wykeham) sharp sand to 1 part NHL 3.5 at lower levels of the repair; 3 parts sharp

sand to 1 part oolitic limestone dust to 2 parts NHL 2.0 to higher levels. Repointing will be 3 parts sharp

sand to 1 part limestone dust to 2 parts NHL 2.0. All NHL, Singleton Birch.

Investigation of the loose brickwork above the newly reinstated brick wall at the eastern corner of the

warehouse showed that this looseness extended to three bricks depth into the wall, which also

contained significant volumes of decomposed timber, bird’s and rodent’s nests. There was little mortar

binding. The lack of bond within this section of wall was of long-standing. The area was consolidated to

full depth once more and repointed. The decomposed timber was probably associated with a roofing

arrangement above and against the stub wall. At the end of a deliberate rebate which may have held a

small roof, there was also a formed socket, three bricks deep which probably held a projecting timber

which will have cantilevered from the building, supporting this roof. This socket was filled and faced

with clay tiles, as a marker.

Repair to the section of the quay further west will proceed upon removal of the tree stump and root at

this point.

The core remains substantially intact, however, and requires refacing with ashlar. The reopening of

Brows quarry – from which the stone for the quay was originally extracted - still having not been

granted, these repairs will of necessity be executed in jurassic sandstone from Aislaby. This is not ideal,

although the weathered stone in this location will look little different to the original. The works must be

completed before the river floods, however, and the scaffold will be vulnerable to destruction or

disturbance by any flooding. It is to be hoped that further essential repairs to either side of the dry-dock

may be executed next summer using stone from Brows Quarry.

Core of quay after removal of tree stump and root. This was, as hoped, of limited penetration into the

solidly constructed core, having grown between this and the coping stones only.

The mortar of the core was coarse, with multiple intrusions of unslaked, or air-slaked lime, charcoal,

brick, limestone dust and sand. This was quite distinct from the bedding mortar, which was probably of

Brows Quarry sand and lime and much finer.

Three heavily eroded facing stones were dressed back in situ to create a solid platform from which to

build the repair. A full width tile repair was laid to the left of this dressing back to the face of another

severely eroded stone disturbance of which would have dislodged or damaged the stonework above.

New stones of a minimum depth of 10” were laid in to these lower sections, tight to the dressed back

faces of the original ashlar.

Thereafter, the core was dressed to accept blocks of

12 – 15 inch depth, ensuring a fully structural

repair of the quay, appropriate to its significance as well as to the demands that will be placed upon it

over time by its proximity to the river.

Original coping stones were fully rebedded in lime mortar, left slightly further apart than originally to

allow for full and reliable pointing of the joints with the same lime mortar and preventing future ingress

of tree (and other) seeds.

Bedding and pointing mortar was 3 parts sharp Wykeham sand: 1 part whitewall limestone dust: 2 parts

Singleton Birch NHL 2.0.

Mortar repairs were applied to the face of some original stones. These were 4 parts ham hill stone dust

to one part sharp sand to 2 parts NHL 2.0.

The existing quay stones were cleared of accumulated soil and vegetation.

The ground behind the copings and between the coping stones and the plinth of the warehouse was dug

down to the full depth of the copings. This had been filled with accumulated organic debris and soil,

allowing colonisation by weeds and trees. This trench of variable width will be filled with a lime

concrete, 2 parts concreting ballast to 1 part St Astier NHL 3.5.

To the east end of the quay, roots from the removed tree stump were chased along the quay where

these extended beneath and had lifted quay copings. Copings were lifted off and reset upon removal of

the roots.

Here and there, tree roots had established themselves within the quay coping stones, exploiting natural

bedding planes and splitting open the stone.

Similarly, tree and ivy roots had penetrated behind the hard opc render applied in the more recent past

– and at variable depth – to the stone plinth of the warehouse. The current intention is that this

unpredictably deep render should be left in situ. However, wherever tree roots can be seen to have

penetrated, this render will be removed and repairs to the plinth carried out before re-rendering with a

lime mortar of similar colour to the original calcareous sandstone of the plinth.

Upon completion of coping and repair works to this section of the quay, scaffolding will be moved to

allow repair of the quay to either side of the dry dock.

To the right hand side, stones have been lost or severely eroded at the lower level, undermining the

sound stonework above. A sycamore seedling has grown in the first joint of the coping, shunting the

corner coping progressively westward.

The corner will need to be dismantled; the stump and associated roots chopped out and the corner

rebuilt, stones replaced as necessary to the same bed-height and joint pattern.

The quay wall as a whole, between the current extent of scaffolding and the corner, will be repaired and

repointed as necessary.

To the left hand side of the opening, a large patch of ashlar is missing, exposing the core (see above).

The ashlar facing will be reinstated to full, structural depth.

A section of the west wall of the ‘dry-dock’ has been lost to leverage from the roots of a large sycamore

tree above, as well as to delamination of stones by fine root penetration of bedding planes and flaws in

the individual blocks. This too will be refaced to a minimum depth of 9”. The large tree stump and roots

will first be removed.