Walking on Flexing Roof | Gibsons

Abstract: Gibsons home inspector note on a roof that flexes underfoot, what this can mean and what can be done about it.

H-Clips Important Structural Element

When you open the hatch to the attic, look up at the plywood or OSB sheathing. Sometimes there is a gap between the sheathing, created by metal spacers. These spacers are referred to as `H-clips`. The product serves two purposes:

  • braces unsupported sheathing edges; and,
  • provides a 1/8″ gap for shrinkage and expansion of roof sheathing.

For the majority of inspections, we do not comment whether they are installed or not because their use is dictated by code or the designer or by the contractor’s standards,  or the roof truss spacing or the sheathing thickness. Surprisingly, using H-clips can increase the load bearing capacity of the roof 4-fold.

Roof Flex Red Flag

However when they are not present, but should have been used, it becomes obvious because the roof is in distress. This shows up as:

  • unusual spring in the sheathing when walking on the roof; and,
  • warping of sheathing which is visible in the attic space.


There is very little opportunity, if any, to remedy the situation. If the roof does not leak then it`s best to just leave it alone. However, the buyers should be fully informed of the situation, in advance of the ‘subjects removal’ date as there may be an opportunity for a price adjustment in the purchase price.