noriker civils ltd. - ribble valleynoriker civils ltd. 10887467, england, 4 pasture barn, skipton...

Project: Hillfoot Cottage structural survey Client: Mr. I. Walton Description: First issue Date: 25 January 2019

Noriker Civils Ltd. 10887467, England, 4 Pasture Barn, Skipton Old Road, BB8 7EP 1

4 Pasture Barn, Skipton Old Road, Colne, BB8 7EP

t: 07871074135 e: [email protected]

Noriker

Civils Ltd.

Structural survey with respect to proposed development at

Hillfoot Cottage, Twiston.

Version: 1.0 Description: First issue for client approval / planning submission

General notes and recommendations

A structural survey of the outbuilding at Hillfoot Cottage was carried out on the 24th January 2019 by

Richard Lines. The survey was concerned with the structural aspects that were visible at the time.

The structure was not dismantled, and it was assumed that the aspects visible were representative of

the rest of the structure. The roof timbers were inspected from ground level and the foundations were

not accessible, with one notable exception detailed in the report that follows.

Any recommendations that are made are from the point of view of the author on the potential for

conversion and does not make any conclusion on the economics of conversion or the likelihood of the

proposals achieving planning permission or meeting current building regulations.

The outbuilding at Hillfoot Cottage is suited to residential conversion, subject to several proposed

structural remediations, detailed below:

• Underpinning of existing walls

• Repointing

• Reinstatement of drainage

• Local rebuilding of distorted masonry in the following regions:

o North elevation – none

o East elevation – bowed area above mullioned window, and depressed area towards

south eastern comer, corresponding to the timber stub embedded internally

o South elevation: None

o West elevation: Depressed area close to southwestern corner

• Calculated verification of existing steel and concrete lintels with respect to proposed

developments

• Replacement of all stone and timber lintels with modern concrete or steel units

• All built in and redundant timber to be removed form inner skin of masonry

• Stitch major internal cracks

Site observations

The outbuilding at Hill Foot Cottage is built on a site which is generally sloping in a northwest to south

east manner, close to several other agricultural and residential buildings. The north western aspects

are cut into the hillside and the south eastern corner is built up to develop a level platform.

One small tree is growing several meters from the south eastern corner. This tree is thought to be

mature in size and not having any obvious effect on the surveyed structure, although subsequent

foundation design should account for the presence of this tree if necessary.

The local BGS borehole records imply that the site is predominantly glacial clay soils overlying

limestone and/or shale bedrock. The site is outside of the coal mining reporting area.

No obvious geotechnical movement has occurred recently, and the site is generally dry and

adequately drained.

The structure is composed of a single main volume which has been formed by removing the partition

wall between two smaller cottages. The roof is monopitch in format and the walls are a traditional

composition of coursed limestone inner and outer skins in lime mortar with a rubble core.

The current owner reported that the roof had been recently replaced and had collapsed in the past.





Noriker

Civils Ltd.

Foundations and floor

The floor is a modern cast concrete system, stepped to create two levels. The owner of the property

advised that the floor was originally bare earth. There is evidence on the western wall that internal

excavations (presumably performed during the recent flooring works) have exposed and undermined

the foundations of the structure. Other than the portion of the western elevation which had been

undermined, the foundations were not accessible during the survey.

Figure 1: Internal view of the western wall, with undermined foundations visible at the base of the wall

Figure 2: Close up showing the termination of the masonry, the supporting soil and the top of the more recent concrete slab





Noriker

Civils Ltd.

Figure 3: Close-up of the undermined foundation closest to the step in floor levels

The foundations in the southwestern corner are particularly vulnerable to failure due to:

• Excavation externally to landscape a flat terrace in the neighbouring garden, effectively

reducing the depth of the foundations

• Excavation internally to develop a flat, level floor area, effectively reducing the depth of the

foundations and in one area, exposing them.

• Dysfunctional drainage which is currently discharging water at the shallow foundations, which

may lead to ground movement or a loss of bearing capacity.

Therefore, the foundations exposed during previous excavation on the western elevation are

considered to be unstable and a suitable foundation should be provided during works if the structure

is to bear the proposed loading safely.





Noriker

Civils Ltd.

Roof

The roof has recently been replaced and is of a timber construction with 230x50mm (9 x 2 inch)

softwood joists at approx. 450mm centres, supporting timber battens and a slate roof. A single line of

nogging and foam insulation has been provided between the joists. Two roof lights have been

installed and no provision of additional trimming joists has been made to support the trimmers. The

roof appears to be functioning adequately. The current roof is not included in the conversion plans;

therefore, no further consideration was given.

Figure 4: Monopitch roof layout, with roof light and insulation

Figure 5: Lack of additional trimming joists to support the trimmers around skylight





Noriker

Civils Ltd.

Walls

The walls are a coursed rubble inner and outer skin format with a rubble fill core and substantial

sandstone quoins. The walls are generally 520mm thick, except for the northern gable which is

considerably thicker, to accommodate the chimney breast. The dressed faces of the stones do not

imply locations of through stones, however no evidence exists to suggest that they are not present.

The masonry is adequately bonded at the intersections and corners where visible, and no evidence

was seen to suggest to the contrary. The masonry joints are generally dry and are in need of

repointing.

Northern:

Figure 6: Northern elevation and retained vegetable garden

The northern elevation is partially obscured by approx. 800mm of retained soil, currently in use as a

vegetable garden. The masonry is generally plumb, free from defect and appears to be functioning

adequately as a retaining wall under the current conditions, likely due to the mass of the combined

wall and chimney breast. One quoin stone on the north eastern corner is showing evidence of spalling

damage and should be replaced. This damage is likely to be related to the stone being laid with its

bedding plane in a vertical sense and the prying action of subsequent freeze – thaw cycles along this

plane of weakness.





Noriker

Civils Ltd.

Figure 7: Freeze-thaw damage to quoin stone

Internally, the northern elevation has a fireplace which has since been partially infilled. The original

timber lintel is still present and should be removed and infilled. The lintel is showing signs of distress

and cracks above indicate that the lintel may have allowed the masonry above to settle. It is not clear

whether this masonry is to be retained in the conversion since it will occupy a significant floor area.

Care should be taken if it is to be removed as the substantial weight and footprint of this feature will

be a key factor in the ability of the wall to retain the vegetable garden.

Figure 8: Masonry movement above the fireplace lintel





Noriker

Civils Ltd.

Eastern:

Figure 9: Eastern elevation

The eastern (front) elevation features a mullioned window and two door openings, one of which has

been infilled.

The masonry is not plumb on this elevation, with some variation in isolated spots which requires

rebuilding. The masonry bows along the length of the wall, with a bulge above the mullioned window

and a depression at the top of the sub panel immediately to the left of the infilled doorway. The

internal wall surface in this area also exhibits bowing which is significant enough to compromise

vertical loadbearing strength and should be rebuilt locally.





Noriker

Civils Ltd.

Figure 10: Crack system above mullioned window

A system of cracks are visible above the mullioned window. The cracks start at eaves level and meet

the window opening and propagates from there in a tapering fashion. These cracks may be due to a

loss of restraint or direct damage caused during the reported roof collapse, or a relic of differential

settlement of the relatively heavy chimney stack gable and the shallow foundations. This cracking

combined with the local bowing is significant enough to require local rebuilding during conversion.

The eastern elevation has a slightly (~30-40mm) thicker construction at ground level. The stones are

larger than the remaining wall panel and are dressed.

Internally, the eastern elevation has regions of distorted masonry, as discussed previously and also

remains of the partition wall between the two original dwellings. The ‘toothed’ remains indicate that a

reasonable bond was built into the masonry and confirms the rubble core construction.





Noriker

Civils Ltd.

Figure 11: Remains of the internal partition wall

A timber stub is present which is likely to have been a structural element in the original roof structure

(e.g. a truss). Damage is evident around this timber which may have been caused by damage caused

by a previous roof failure. As specified previously, this area of wall should be rebuilt locally and the

timber removed.





Noriker

Civils Ltd.

Figure 12: Damage to internal masonry around the projecting timber stub

Figure 13: Bowing masonry round timber stub





Noriker

Civils Ltd.

Southern:

Figure 14: Southern elevation

The southern elevation has been partially rebuilt relatively recently with matching stone and cement

mortar. The wall panel is plumb and in reasonable condition.





Noriker

Civils Ltd.

Western:

Figure 15: Western elevation

The western elevation features one small window opening and is free from any significant external

cracks, although the lack of mortar in the joints makes identification of cracks difficult.

The masonry towards the southwestern corner is exhibiting a significant bowing depression,

approximately in the same location of the area where the foundation has been undermined. This

depression is significant enough to influence the vertical loadbearing capacity of the wall and should

be rebuilt locally during conversion. Otherwise the masonry is generally plumb.

The rainwater goods no longer function, and the water collected by the roof is currently draining

directly onto the soil which is bearing the loads of the shallow/undermined foundations. No formal

drainage for the rainwater pipe exists. Proper drainage should be reinstated.

A stub of steel is visible at a location coinciding with an abrupt change in ground levels. This is not

part of the structure and may be a relic of a previous lean to shelter or canopy roof. The abrupt

change in ground levels may have been related to a previous attempt at levelling the ground

underneath the canopy roof and it is suspected that some masonry (with a different character to the

surrounding) has possibly been added at ground level to serve as a form of underpinning to avoid

exposing the foundations during excavation.

Internally, the western elevation features a prominent vertical crack feature at the other (internal) end

of the steel section described in the preceding paragraph. The masonry above this steel section has

been rebuilt relatively recently. The crack has not re-appeared in the more recent masonry repairs,

and the underlying movement is therefore assumed to be extinct. The nature and location of the crack





Noriker

Civils Ltd.

imply that it may be related to the foundation issues discussed previously. The crack should be

stitched during conversion with a suitable product1.

Figure 16: Crack adjacent to undermined foundations on western elevation, noting repair above the embedded steel beam stub

Openings

North:

None

East:

The mullioned window and door opening both have a stone lintel and jambs externally, and one or

more timber lintels internally. The infilled doorway also has a timber lintel internally. Without exception

the timber lintels are rotting and all (including the infilled doorway) should be replaced with concrete or

steel units. The stone lintels should be replaced by a modem concrete or steel unit.

South:

The garage door opening is supported by three steel beams and the western end has a 130mm

bearing (170mm internal), whereas the eastern end has a 170mm bearing internally and externally.

These beams are currently performing well but should be verified by calculation for their capacity to

bear the loads imposed by the proposed developments, paying close attention to the bearing stress

imposed on the supporting masonry.

West:

The window has a stone lintel on the exterior face, and a concrete lintel on the internal face which is

directly bearing the roof joists. The stone lintel should be replaced by a modem concrete or steel unit

and the concrete lintel verified for loadbearing capacity under the loads imposed by the proposed

developments (if possible).

1 https://www.twistfix.co.uk/crack-stitching-bars?cat=7052

noriker civils ltd. - ribble valleynoriker civils ltd. 10887467, england, 4 pasture barn, skipton...

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