A typical replacement project will involve erecting a scaffold tower or work platform, taking out the first course of roof tiles and then removing the existing timber roof line before the installation of the new plastic boards can begin. The process is completed by installing a new gutter system and a rigid eaves felt tray before laying the tiles back onto the roof. However as with all building work there are methods that can cut down the amount of work involved – saving the homeowner money. These options are often chosen by the homeowner either to save on costs or through a lack of knowledge regarding roofing work. Over capping is one of these procedures.
Capping or over cladding as it is more commonly called is a method of roof edge construction where the original timber boards are left in place and the new upvc plastic system is simply fixed to the old. This method is considerably cheaper than removing the old timber. The work can be easily achieved off a ladder and the roof tiles do not need to be removed thus work hours are reduced. UPVC plastic fascia boards used in this method are also much cheaper simply because they are thinner. These boards are not supporting the roof tiles so there is no need to use a more expensive load bearing board.
This may seem an attractive option for the home owner however there is a catch.
Chances are the existing boards need to be replaced because they are at the end of their life and painting is no longer a viable solution. Fixing a thin capping board to an unsound sub structure is a disaster waiting to happen. Any existing rot will spread rapidly as it is sealed in by the plastic without any ventilation. Even if no rot is currently present the existing external timber boards will hold some moisture that will be trapped by the capping board leading to eventual rot.
There are many other problems with the over clad method such as how the finished work will look like if you live in a terraced or semi detached property. There will be a ‘step’ on the boundary between the two properties. The gutters will not be perfectly in line between the two properties leading to a potential leak.. It is also worth noting that many window frames are only a few millimeters below the roof line, over cladding the existing boards could prevent some windows from fully opening – a serious problem should the window be a designated fire escape route.
The capping method also reduces the overhang of the roof tiles at eaves level and can result in rainwater running behind the guttering. Because the over cladd method is completed without the removal of any roof tiles new eaves felt is rarely installed. This type of felt is used to overlap into the guttering it can prevent water from running behind the guttering and should the property suffer a broken tile any water will be guided down the roof and into the gutter not onto the ceiling.
UPVC products are designed to last many years. Most manufacturers and indeed many installers offer a ten year guarantee on the materials. However to date we have yet to find a company that will offer a guarantee on the timber structure these UPVC boards are fixed to. Fixing to a sound structure is the most important factor for a successful long lasting installation. It is highly unlikely that a claim on any guarantee will be successful if the cause of the problem isn’t the plastic itself but rather the old boards hidden underneath becoming rotten.