All you need to know about having a roof valley repaired or replaced including costs of materials, costs of labour and time frames.
The roof valley is that part of the roof where two sloping roofs meet together, where rainwater has to be channelled downwards into a gutter. These roof valleys have to deal with a lot of water during heavy rainfall and are prone to leaking. Roof valleys are usually made from lead, concrete tiles or fibreglass. The method of repair will obviously depend on the materials used in the construction, but could involve a minor repair or complete replacement.
Once it has been established that the roof valley is damaged, then the first step is to remove the tiles/shingles along the valley which will allow you to remove the valley flashing. Take care to only lift up as many tiles as you need to get the new flashing into the roof. Then carefully fit the new flashing over the connection between the roofs and fix in place using mechanical fixings or concrete depending on the type of valley. If using cement or a waterproof adhesive then leave the flashing to dry completely before you start replacing/refitting the roof tiles, throwing away any damaged tiles and fitting new ones.
When any work is being carried out on a roof, a full inspection should be carried out on the roof tiles, flashing, chimneys, fascia/soffit and guttering. Labour is often the most expensive part of a quote for any roof related repairs, so it makes sense to get any roof repairs done at the same. In addition, tiles will quite possible be disturbed/broken during a repair to the roof valley, so spare tiles should be on hand prior to starting the job.
In the majority of cases, a complete replacement of the roof valley and cement is the best option. However, sometimes the roof valley itself is in good condition but the cement is in poor condition and crumbling, so it can in some circumstances be possible to just re-bed the tiles onto new cement, leaving the existing valley in place. But if the base for the roof valley is concrete tiles, then they will almost certainly need to be replaced as it is almost impossible to repair concrete tiles and they are prone to leaking.
A full replacement of the valley will involve removing all the tiles, all the cement and also the under-felt (which is usually rotten anyway). If you have a bad water leak coming from a faulty roof valley, where water is staining the ceiling of the floor below, you need to replace your roof valley before serious damage is caused to the building structure. Lead valleys can be repaired which is handy as they are a particularly difficult to dispose of being toxic.
With any job where roof tiles are removed, you will find that some are damaged, or you will actually break them in the process or removing/refitting - so always have spare tiles to hand. Though most tiles are not expensive so this is not a major problem in terms of cost. If the existing valley flashing is lead and this needs removed then do not simply through this away! Lead is toxic and needs to be disposed of correctly, but you may find your local scrap merchant will actually pay you for any lead flashing you have that is surplus to requirements!
To replace cement only and re-use existing valley flashing, then you are looking at around £300 to £375, for a full replacement add on around £100-150. This assumes typical replacement with cheap easy to access roof tiles and easy access to both the house and the roof valley itself.
Most roofers work in pairs and usually charge around £250 per day between them. In terms of times frames you're looking at around 4-6 hours to repair a roof valley or around 6-8 hours to fully replace.
Here are a few average costs for hiring someone to repair/replace a roof valley:
|# of Valleys||Repair/Replace||Avg. Cost||Duration|
|1||Repair||£350||1/2 a day|
Individual costs for hiring a roofer to replace a single roof valley - Total Cost: £450