On this page we will show you all the different aspects of a roof, explain what there function is and how over time they can stop functioning correctly and explain the consequences of this.
The ridge tiles run along the top of the roof (the ridge). It is the job of the ridge tiles to seal the joint between two elevations of the roof, generally this is the front elevation and the rear elevation. Some times roofs can have more than two elevations and the same type of tile is used to seal the joint only instead of running across the top of the roof they run down the corners of the roof, these are called hip tiles. Generally hip and ridge tiles are bedded on top of a concrete or mortar bed.The ridge tile bed serves to seal the joints between the individual ridge tiles and to hold the ridge tiles firmly into position on the roof. Over time this mortar can erode leaving exposed gaps in the pointing, these gaps become larger at a steadily increasing rate over time as more of the mortar is exposed to the elements. If left unmaintained, the ridge tile pointing can fall out and the ridges concrete bed can erode away leaving the ridge exposed to penetrating damp. In the worse cases, high winds can blow ridge tiles off a roof damaging other parts of the roof, people or property as it goes.
Roof tiles or roof shingles are generally rectangular shaped tiles individually laid from the bottom of the roof with the layer above over lapping to prevent water from getting behind or under each tile. The main function of the tiles is to make the main body of the roof water tight. There are many different types of roof shingles and each type have there own way of failing over time. Terracotta tiles (also known as rosemary tiles) can often erode and loose their smooth face. Slate tiles slip out of position when the copper nails that hold them into place erode or the wooden lats that they are nailed into rot. Slipped or missing roof tiles create holes in the roof which will cause penetrating damp.
Flashing is the used to seal joints in the roof, generally this is when the roof meets masonry. The most common material used for flashing is lead. Probably the most common problem with lead flashing is it expands and contracts at different temperatures, this causes the mortar joints that the flashing laps onto to crack and eventually fall out of the masonry. Once this happens rain water running down the masonry can get behind the lead flashing causing penetrating damp inside the property. In the worse case, the lead work can fall out of the masonry completely leaving the join that was once sealed completely exposed to the elements.
Hip tiles are the same type of tile as a ridge tile, they are secured to the roof on top of a concrete bed and just like ridge tiles and it is there job to make the roof water tight where two different elevations meet with a convex joint. The differents between a ridge tile and a hip tile is there position on the roof, hip tiles can be found running down the corners of a roof whereas ridge tiles run across the top of the roof. Common problems with hip tiles are the erosion of the concrete bed and pointing.
Bonnet tiles carry out the same job as hip tiles only they are secured to the roof with nails, starting from the bottom of the roof they are nailed into postion, the next bonnet tile then overlaps the one prior making the joint water tight. Common failures with bonnet tiles are the nails holding them into postion become loose over many years and the bonnets can slip off the roof.
Valleys seal the roof where two elevations of the roof meet on a concave angle. Often valleys are lined with lengths of lead over lapping each other from the bottom upwards. Common problems with lead valleys are over long periods of time small holes and fractures appear in the lead due to the constant expansion and contraction of the material in different weather conditions. When these holes and fractures start to appear water can seep in causing penetrating damp inside the property. Another common problem in valleys is the pointing between the lead and the tiles that run into the valley, the pointing can often crack and fall out from under the tiles leaving the edge of the valley exposed to penetrating damp as water flowing down the valley can often force its way under the tiles and via the leadwork.
The verge end is the edge of a roof known as the apex or gable. It is where the roof tiles meet the brickwork on a property. On most properties the verge is sealed using mortar or concrete but a lot of modern properties seal this joint using a dry verge system which is basically a plastic covering. The most common problem found on the verge end is missing or weak pointing. Holes in the verge end can result in penetrating damp when rain water is blown though the gaps, or even infestations of insects or if the gaps are large enough, birds.