STRUCTURAL REPORT, JANUARY 2008

CLARKE, NICHOLLS & MARCEL REPORT

STRUCTURAL CONDITION REPORT ON THE CHURCH OF ST JOHN, KATES HILL, DUDLEY

1.0   BRIEF

1.1   Our brief was to carry out a structural survey  to determine the condition of the fabric of the Church of St John following closure of the church on safety grounds as recommended in the quinquennial report of 2002.

The survey was generally visual, with a limited amount of opening up carried out to assess certain elements.

We have not inspected woodwork or other parts of the structure which are covered, unexposed or inaccessible and we are therefore unable to report that any such part of the property is free from defect.

A specialist timber decay analyst was also in attendance to inspect various timber elements.

1.2   Two previous reports were made available - namely a structural condition report by Ascough and Associates dated February 1993 and a quinquennial report upon the fabric under the inspection of churches measure 1955, dated November 2003.

2.0   OBSERVATIONS - External

2.1   The church built in 1840 is constructed with substantial masonry walls with a generally limestone face stone and brick backing. The external stone face had sandstone window and door dressings and buttresses. The pitched roofs were essentially at four levels the Chancel at the east end, the vestry and Organ Chambers at the east end and the lower nave and upper nave pitches with clerestory windows between. The church Tower was located at the south end.

The building is located on an elevated part of Dudley leaving it fairly exposed to weathering.

2.2   The roofs are covered in relatively recent Marley concrete tiles, replacing the original slate covering. Both upper and lower level Nave roofs have good roof lines with no noticeable sagging at the upper level and only very minor noticeable deflection between supports along the lower level. The Chancel roof again shows little signs of deflection, similarly for the Vestry and Organ Chamber roofs  either side of the Chancel at a lower level. There was considerable deflection and a number of displaced tiles noted to the roof over the south tower access stairs. A few tiles were missing on the upper nave roof on the south pitch and also from the Chancel roof against the east wall of the Nave.

2.3   The Tower roof was not available for inspection.

2.4   The main wall panels constructed in limestone were generally plimb and in good condition and appeared to have been relatively recently repointed, albeit with a fairly hard mortar. There were areas of wall that exhibited advanced weathering noticeably the east vestry wall particularly around the window arch where there were open joints. There was similar advanced weathering to the west tower stairway wall.

2.5   However there were more significant weathering problems with the sandstone window and door dressings and buttresses particularly but not exclusively to the south and west elevations. The surfaces of some stones had laminated with a potential to fall.

2.6   Local defects to the walls were noted to the east and west Chancel walls which exhibited an outward lean noticeably just above the the incoming buttressing Vestry and Organ Chamber walls.

2.7   A significant piece of stone was missing at the base of the wall to the Organ Chamber leaving a large gap.

2.8   A minor diagonal crack was noted at the head of the north Chancel walls extending from the east corner downwards.

2.9   A number of defects with the rainwater goods were noted. The gutters were supported on small regularly spaced sandstone corbels or continuous sandstone corbels. Deterioration of the sandstone supports were evident more particularly on the south elevation making the gutter supports questionable. The size of the gutter to the upper Nave roof appears too small for purpose. Vegetation growth was evident in extremes of the gutter on the south and north elevation and in a hopper head on the north elevation, which had led to a significant water staining to the complete wall height. Missing sections of downpipes were noted on the east and west extremes of the north elevation. The majority of gullies at ground level were blocked with debris.

2.10   Viewed from the ground lead flashings to the lower Nave roof to wall abutment appeared to have some loose mortar pointing and appeared to lack height at its extreme ends. At the west end of the north elevation adjacent to the tower there appears to be no leas flashing between the roof tiles  and parapet coping for a short length of parapet.

3.0   OBSERVATIONS - Internal

3.1   The internal condition of the roofs appear to reflect the generally good line of the roof externally. The high Nave roof is fully boarded with rafters onto a single purlin on each pitch supported by regularly spaced arch-braced collar beam trusses. The two middle trusses of this long roof had metal eaves tie bars, probably inserted as a precaution to potential roof spread after original roof was raised to form a clerestory. There was no visible evidence of any structural movement to this roof, when viewed from the ground. However at the time of inspection decay was observed by the timber decay analyst in three trusses (subject of a separate report).

3.2   The low Nave roofs over the balconies were formed by a series of mono pitch timber trusses. There were cast iron corbel supports at the outer walls, however it appeared that the truss tie was built into the wall. The moulded plaster bases of the corbel supports had fallen off on several trusses to reveal projecting sandstone corbels. The ceiling was boarded to the pitch of the roof.

3.3   On the south side the lower ceiling boards had been replaced during reported dry rot rectification work. Removal of one ceiling board showed "new blockwork" built up to pick up ends of the ceiling joists wrapped in felt. A void over the ceiling revealed roof support rafters in good condition on to a substantial wallplate. The roof was felted, the felt in good condition. As part of the previously carried out remedial work two trusses had been strengthened with steel plates.

3.4   Minor decay is thought to be evident to one truss on the north side again subject to a separate report.

3.5   The Chancel roof is fully boarded with rafters onto a single purlin on each pitch supported by regularly spaced trusses alternating arch-braced collar beam and collar beam. There was no visible evidence of any structural movement, however there may have been some historical movement as observed externally on the upper levels of the walls and as noted in paragraph 2.6

3.6   The vestry roof is a mono pitch with a single centrally placed purlin. Removal of the plaster lath ceiling revealed a damp decayed first rafter, and a likely affected purlin bearing.

3.7   Access to the Organ Chamber roof was very limited and therefore no particular observation made. Access to the Tower was not available, however the Tower access stairway on the south side revealed quite severe damage from water penetration, reflected by the condition of the covering noted in paragraph 2.2.

3.8   Internally the walls were plastered. Whilst the walls were generally plumb there were significant areas of damp which has led to the deterioration of the paintwork and in some areas deterioration of the plasterwork. Where there were noted defects externally to rainwater goods this was reflected internally - particularly the east nave wall at high level at the north end, the north wall at the missing downpipe, the east vestry wall and the west tower stairwell - these areas indicated the worst conditions. However there were large areas where paintwork was deteriorating generally and particularly in the Chancel.

Appearance of dampness was quite prevalent.

3.9   Some cracks generally small in nature were noted in the Chancel around arch windows and indeed some displacement of the arch stonework at the head of the windows was observed.

3.10   Limited inspection of the undercroft to the nave revealed timber floor joists supported on a series of brick arches and vaults. Due to limited light full inspection was not possible but there were no apparent defects to suggest any substructure problems.

3.11   Of note is the distortion of a significant number of stained glass windows.

3.12   Our inspection is limited to the fabric of the building. The boiler house was not accessible being fenced off on closure of the Church. Boundary walls have also not been included.

4.0   CONCLUSIONS AND RECOMMENDATIONS

4.1   In general terms our observations of the structure concur with those of Ascough and Associates report of 1993 and the quinquennial report of 2002.

4.2   In our opinion the building is not a significantly dangerous structure, and can be repaired and brought back into service. At this stage, however the potential for falling stone does remain.

4.3   The problems with the building are essentially twofold. The walls of the building have two materials - limestone and sandstone. The deterioration of the softer sandstone has led to a number of problems the most significant is the breakdown of the stone which can laminate and fall. Water soaked into sandstone exerts a lot of pressure on freezing which leads to the splitting of the stone. This we believe is a contributory factor to the distortion of the windows, the limestone resisting the pressure exerted by the sandstone therefore damaging the weaker element.

The damage to the sandstone is an ongoing problem and is one that cannot be prevented but only maintained and periodically having loose stone removed and ensuring that the mortar pointing is maintained in good condition. The distortion of the windows is an Architectural detailing problem and appears to be one of estimating the amount of potential movement of the sandstone and allowing suitable or providing suitable tolerances.

4.4   The second problem is that only  very limited maintenance work appears to have been carried out over a substantial period of time and certainly none recently. The amount of damp in the building is significant and has relatively easily identifiable sources such as breakdown of mortar joints to lead flashings at abutments, vegetation growth in gutters allowing water to spill down walls, missing or displaced roof tiles, missing flashings (as identified in parapet 2.10) allowing water to penetrate, missing rainwater downpipes allowing water to soak walls, blocked hoppers allowing water to spill down the walls and advanced weathering of mortar joints leaving open joints for water to penetrate. Also blocked gullies will lead to ponding of water around the building.

4.5   Coupled with the above it would appear that the size of the gutter particularly at the high eaves appears inadequate in size or design to cope with water from the roof.

It is imperative that as a matter of urgency the above problems are fully identified and rectified so that the necessary repairs to the building can be carried out.

4.6   Whilst the above are not structural problems in themselves they can certainly lead to a deterioration in the structure. The situation at this stage is not irretrievable but a large amount of maintenance type work needs to be carried out urgently to prolong the life of the fabric.

4.7   The deterioration of the structure due to lack of maintenance is clearly in evidence from our observations of the extensive damp evident on the walls and indeed some decay was noted to roof timbers particularly to the Vestry and the south west Tower stair enclosure. Cure of the problem is essential to enable repairs to be carried out and prevent any further deterioration.

4.8   It is noted that, subject to other reports, there are areas of decay to three of the truss principals to the Nave roof. Whilst there are no visible problems with the roof, repair is advised as a priority. It is likely that the arch braces assist the decayed principals indicating a degree of redundancy in the design. Similarly any decay to lower Nave roof members should be dealt with.  

4.9   Both Nave and Chancel roof trusses being the principle means of roof support are of a form (arch-braced collar beam trusses and collar beam trusses) that can be susceptible to spread. This does not appear to have occurred on the Nave roof which is of a reasonably steep pitch is relatively narrow and is boarded which will add to stiffness. It also benefits from eaves tie bars having been installed at the two mid trusses.

The Chancel roof however appears to have suffered some spread as evidenced by the outward lean of the north and south external walls towards the top at mid length. the damage has been limited by the incoming Vestry and Organ Chamber buttressing walls. The movement we suggest is historical. This roof does not have the benefit of any eaves ties and two of the trusses do not benefit from having arch-braces. we believe this roof will benefit from some form of eaves tie similar those in the Nave roof.

4.10   We do not believe that the latest roof covering to be of influence to the movement of the Chancel roof.

Without knowing the weight of the original slates, it may be that the new covering is up to 100% heavier or conversely may not be any heavier at all. There does not appear to have been any significant deflection to any of the main roof structures as a result of the work to the roof over the period of 1969 - 1991.

Therefore it is our opinion that the imposed roof loads are unlikely to cause overstress in members unless they have reduced capacity due to defects. If the member sizes can be obtained, their suitability can be checked by calculation, if desired.

4.11   The following is a summary of recommendations that should be carried out to bring the building structure back into service.

(i)   Carry out remedial measures and re-pointing to the sandstone elements of the walls.

(ii)   Check capacities and conditions of gutters, replace or repair as necessary and clear out all vegetation.

(iii)   Check all lead flashings for integrity and repair or replace as necessary.

(iv)   Replace missing rainwater pipes.

(v)   Clear out all blocked gullies and check rainwater discharge underground.

(vi)   Replace defective roof tiles.

(vii)   Rake out and re-point all open mortar joints.

(viii)  Replace defective/decayed timber to the roof structures (note that this is the subject of a separate report).

(ix)  Provide a design check of the roof members, if desired

(x)  Consider insertion of eaves tie bars to the Chancel roof trusses.

 

END OF REPORT