Rafters or ridge beams sagging

Causes

Rafter spans too great for the timber size and/or roofing type, or roof framing has been overloaded

Poor quality timber, or cracked or broken timber

Timber has rotted due to roof leaks or high roof space moisture levels

Light roof cladding has been replaced with a heavy roof cladding 

Internal wall has been removed

Listed under: Interior, timber and wood-based, timber, Roof, cladding, framing, roof space, moisture, durability, rot, roof cladding, leaks

Cause

Rafter spans too great for the timber size and/or roofing type, or roof framing has been overloaded

Repair

  • in older houses such as villas it is not unusual to find structural timbers that are undersized compared to today’s standards

  • get professional advice from an architect or engineer to determine the best solution

  • depending on the circumstances, repair work may include installing new underpurlins or struts or fixing new timber plates to both sides of sagging or damaged framing

  • new radiata pine timber should be treated to H1.2

  • in some cases, options may include using engineered steel beams or LVL (laminated veneer lumber) beams – it is often possible to conceal these within a roof space

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Cause

Poor quality timber, or cracked or broken timber

Repair

  • as above

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Cause

Timber has rotted due to roof leaks or high roof space moisture levels

Repair

  • first, address the moisture problem. Identify and repair any leak(s). If the location of the leak is difficult to find, or there may be multiple leaks, call a registered building surveyor to investigate and recommend solutions

  • moist air may be entering the roof space from:

    • the subfloor (possible with older brick veneer cavity walls. Block off the area at the top of the wall where there is no wall underlay or block off at soffit level if there is wall underlay. This is to stop damp subfloor air getting into the roof space)

    • ceiling holes cut for downlights in kitchens or bathrooms – replace the downlights with IC or IC-F downlights, or with ceiling-mounted lighting

    • extract fans venting into the roof space – vent the air to the outside through an external wall, roof or soffit vent

  • get professional advice from an architect or engineer to determine the best structural framing solution

  • all rotted timber should be removed

  • new radiata pine timber should be treated to H1.2

  • in some cases, options may include using engineered steel beams or LVL (laminated veneer lumber) beams – it is often possible to conceal these within a roof space

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Cause

Light roof cladding has been replaced with a heavy roof cladding 

Repair

  • get professional advice from an architect or engineer to determine the best solution

  • depending on the circumstances, repair work may include installing new underpurlins or struts or fixing new timber plates to both sides of sagging or damaged framing

  • new radiata pine timber should be treated to H1.2

  • in some cases, options may include using engineered steel beams or LVL (laminated veneer lumber) beams – it is often possible to conceal these within a roof space

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Cause

Internal wall has been removed

Repair

  • get professional advice from an architect or engineer to determine the best solution. This may include additional support in the roof or inside the house to provide the structural support that the old wall provided

  • new radiata pine timber should be treated to H1.2

  • in some cases, options may include using engineered steel beams or LVL (laminated veneer lumber) beams

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