Inspection (L3) Sewerby Zoo, Block E

Question 1

What was the background leading up to the clients instruction?

Answer 1

The pitched roof was dilapidated and although repairs had been undertaken over the years it was due for renewal and was included for consideration on the planned maintenance programme.

Question 2

What was the roof construction?

Answer 2

King Post Roof Truss

Question 3

What are the elements that make up the structure of the King Post Truss?

Answer 3

• King Post
• Principal Rafters
• Stone template
• Purlins
• Purlin Cleats
• Wall plate
• Common Rafters
• Ridge Board

Question 4

Can you provide a sketch?

Question 5

Can you explain the construction of the building.

Answer 5

• The building was constructed early seventeenth century comprising of traditional brick step foundations, solid brick walls supporting a king post truss roof. The roof was a hip roof with diminishing slate coverings.
• The building was used as animal pens and zoo kitchen.

Question 6

What was the impact of the building being within the curtilage of a listed building?

Answer 6

• The building was constructed before July 1984 so by law, is considered as part of the listed building.
• Due to this reason, I consulted with the Conservation Officer.

Question 7

Can you talk me through the process of your inspection?

Answer 7

• Prior to attending site to carry out an inspection, I already had an ample amount desktop survey information collected over the years such as, structural report with accommodating photographs, previous repairs and drawings.
• I proceeded to carry out an on-site inspection to ensure the information was correct and to collect further information.
• I assessed the surrounding area taking notes and photographs for:
• Contractor site set-up including welfare, toilets and skips
• Any restrictions for delivery of materials
• Restrictions on contractor parking
• Areas which require closure due to scaffolding

I consulted with the Site Manager for any consideration to ensure the Zoo continues to operating with minimal disruption as practicably possible.

Question 8

Why was it evident repairs were required?

Answer 8

• A structural engineers report was undertaken 12 months prior to me receiving an instruction from the client.
• The structural engineers report clearly showed repairs were going to be required.

Question 9

Why did you advise the client to include a Provisional Sum and how did you arrive at your figure?

Answer 9

• I advised the client to include a provisional sum from the information available and from my on-site visit, however, the extent was unknown until the roof coverings were stripped.
• I had a rate for timber repairs from a similar project I was involved in to replace the pitched roof coverings to a farm building.
• I estimated that 25% of the rafters would require some form of repairs or replacement.

Question 10

What did you do with the existing slate coverings; could they be reused?

Answer 10

• The existing slates were around 300 years old. The undersides had delaminated and become friable. This information was gathered over 12 months of carrying out reactive repairs.
• Prior to tender I had a discussion with the Conservation Officer, and he was happy for the slates to be replaced on a like-for-like basis which was West Morland Green Slate.

Note to self: the main house was constructed in 1714 (Historic England)

Question 11

Talk me through the process of how you inspected the timber members.

Answer 11

• Once the roof was stripped and the timber members exposed, I had a walk around with the Conservation Officer and contractor to mark-up the timber which required repairs or replacement.
• I started from one corner of the building working my way around inspecting the timber members as I went along.

Question 12

What equipment did you use?

Answer 12

• Hammer and a flat blade

Question 13

Did you refer to any guidance?

Answer 13

• I referred to the BRE Good Buildings Guides and Good Repair Guides.

Question 14

How did you know it was insect attack?

Answer 14

• I could see small cluster of round flight holes to the side of the hip rafter and top of the dragon tie.

Question 15

Explain your process for confirming the insect attack; how did you know if the attack was active or inactive?

Answer 15

• I examined around the area of the flight holes to look for any frass, but none was found.
• I tapped the timber to the area affected to see if there was any fresh frass and to establish if the damage caused required repairs.

Question 16

What repairs did you carry out to the dragon tie/hip rafter?

Answer 16

• The timber was in a sound condition and did not require any repairs.

Question 17

What is a dragon tie and what purpose does it serve?

Answer 17

• It is a horizontal, diagonal beam which supports the hip rafter and it is to prevent the wall plate from spreading where the load is transferred down the roof.

Question 18

What were the indicators that led you to believe the rafters had been affected by wet rot?

Answer 18

• Dark brown staining and longitudinal cracking. It was evident these areas had little protection due to the missing slates.

Question 19

What were the repairs you undertook?

Answer 19

• Where full length rafters were beyond repair, I agreed with the Conservation Officer to leave them in place and butt the new timbers up against the old.
• Where the rafters above or below the purlin required repair, I removed the damaged section of timber and replaced with new.
• There was also a small area of mop-stick which required replacing.
• The Conservation Officer was happy for with green treated timber.

Question 20

How did you finish the ridge and hip details?

Answer 20

• The ridge was a mix and match of original lead and patches of flashband from past repairs.
• The lead was beyond re-use due to expansion splitting.
• I decided to replace with new

Question 21

How did you install the lead?

Answer 21

• I installed code 5 lead to the ridge and hip rafters
• Maximum length of lead no greater than 1500mm with a minimum 100mm overlap
• Minimum lapping onto slate 150mm
• I referred to The Lead Sheet Association