Roof Rafter Spread

N modern cut timber roofs pre 1970 constructed on site this force is normally resisted by joining the bottom of each pair of rafters see fig.

Roof rafter spread.

This ties them together and prevents any outward movement. When considering what to do about sags in a roof start by noticing if the sag is in sheathing between rafters page top photo0 or sagging along the length of the rafters. Roof spread can be dangerous for a house and very damaging for a roof. Please follow and recommend our blog page.

Therefore the first signs of roof spread are often cracking bulging or leaning at the head of the masonry causing bowed walls. Factors that cause the situation include bad construction improper materials and water and rot problems. It also leaves a void the loft which can be used for storage or the placing of water tanks etc. This is referred to as roof spread.

Roof spread affects a roof that begins to move after it is installed. Something else to look for in regards to roof spread is sag. Roof spread occurs when there is a failure to adequately support the main rafters of the roof so as to prevent them spreading further open in a scissor type action. Roof rafter decking sagging.

Since the rafters are fixed to timber wall plates sitting on the head of the masonry wall then roof spread pushed out those wall plates in the process pushing out the masonry below. Roof spread occurs when the principal rafters of the roof are not adequately supported causing them to open in a scissor like pattern. This article describes a diy repair project using a site built spreader to straighten sagged roof rafters and decking. If looking for the obvious and common cause of roof spread then this particular issue could so easily have been missed especially when limited to a head and shoulders inspection from the loft hatch.