Parklands Road

Letter Report: Existing Roof Space Inspection

Letter Report: Existing Roof Space Inspection

The structural inspection report has been prepared on the instructions of Jon Gill our client. We have been requested by our client to carry out a site inspection on the existing roof space as there has been some movement. The visual survey was undertaken on the morning of the 28th of February 2019. The inspection took place internally within the roof space and the weather was cold and wet. No intrusive investigations were carried out at this stage.

The following other limitations in respect of this report should also be noted:

  • The inspection was carried out from within the rear of the property at ground floor level.
  • The inspection was of a purely visual nature.

Services within and to the property have not been inspected. In accordance with our standard practice we must point out that this report is based upon our inspection of the premises and any other information made available to us, both written and oral, which we have assumed to be correct.

This report is intended primarily for information and is to be read in conjunction with any other specialist reports and investigations. The report is for the benefit of Jon Gill our client. Structural Engineering Services cannot accept any liability to any third party for the whole or part of its content.

Timber Elevation

Project Details:

Structural Letter Report: Roof Space Inspection 

Completion Date: March 2020

Building Type: Residential

Project Type: Structural Report

Location: Parklands Road, London

Structural Engineer: John Murphy

Brief Description of The Existing Property

The property at No.39 is a two-story terraced house located on Parklands Road, London. The houses within the street are formed of masonry wall construction generally with timber floors to all levels and timber roof construction originally covered in slates but the roof is now covered in concrete tiles and these were changed approximately 30 years ago. The adjacent properties are constructed in a similar way.

Defects Recorded Within The Existing Roof Space

The existing roof is constructed with timber rafters which are supported at roughly mid-height off timber purlins which are supported via diagonal bracing members back down onto the central load bearing wall, this is a traditional form of roof construction for properties of this age and type.

There are three sets of diagonal bracing within the existing roof construction, one pair centrally located, one pair against the Party Wall above the access hatch and two smaller diagonal props built off the existing gathered chimney breast. The ends of the purlins are not built into the Party Walls which is unusual and stop short of the wall which is unusual as they are normally built into the walls or supported off cantilever stone elements.

Over a long period of time the roof framing has spread due to the increase in load from the tiles. The original slate tiles would weigh significantly less than the current concrete tiles which has overstressed the existing roof and supporting members. There is noticeable bending and deflection within the purlin members and there has also been excessive movement to the rear diagonal prop off the existing gathered chimney breast.

The movement to the rear brace off the chimney is in the region of 30mm to 35mm indicating that where the front of the roof has spread the rear section of the roof has also moved. (Refer to picture 7). The area of rafters to the front of the property located above the entrance area have moved out and this is clearly visible both internally and externally as viewed from the street level.

Conclusion & Recommendation

Conclusion:

As highlighted above the roof has been suffering from roof spread which has been taking place for a sustained period of time. Based upon the level of movement, we would recommend the following remedial works are undertaken within the existing roof space to stabilise the roof framing.

  • Installing two areas of further diagonal bracing to limit any further movement and to limit any further deflection taking place within the existing purlins. These members can match the existing bracing. 50mm x 100mm Grade C24 timber elements can be used. The braces should be located between the existing three sets of diagonal braces.
  • Install high level 50mm x 100mm timber collars between the existing rafters and fixed into position using a minimum of 4 No 4.50mm diameter wood screws x 75mm long. The collars should be located approximately 600mm below the underside of the existing ridge board.
  • Reconnect the existing rafter feet onto the existing timber wall plate. This can be carried out after the front fascia boarding has been removed and the ends of the rafters and plate can be clearly seen. Galvanized framing angles or similar fixings can be used, fully fixed into place.

Following the completion of the remedial works the structural integrity and stability of the existing roof structure will be stabilised thus limiting any further movement.

Recommendation:

  • A full CCTV survey report is carried out on all the local drainage to assess for any damage or leaks. If damage or leaks are found, they will need to be repaired as per the drainage report.
  • The trial hole dug indicates there is no discernable foundation so localized underpinning will be required to
    stablilise the chimney. This can be carried out externally with minimal disruption to the existing property.
  • Once the underpinning has been completed, we would suggest the following remedial works be carried out on the damage to the property:
    • Localised rebuilding works to the base of the chimney to reinstate the damaged and loose brickwork. It may be
      feasible at this stage to try to realign the brickwork where it has moved previously and this may involve some
      temporary propping to facilitate this.

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