Bedding or Re-Bedding a Roof
Have you got cement deteriorating away from your ridgecapping or loose mortar becoming detached from areas? You might have ridgecapping sliding down your roof line or into your valley flashings. Well it may be time that some re-bedding is required.
Does my roof need re-bedding?
A roof inspection can be carried out to get an idea of the condition of the bedding. A poorly made bedding mix will usually be crumbly or powdery. Sometimes the bedding may be so deteriorated that there is no cement under the ridge capping at all. Other times the bedding cement may have started to slide out from under the ridge slightly. In this case, the cement would be too unstable to re-use and would need to be re-bedded. Usually a good cement mix for re-bedding is about four parts of sand to one part of cement.
Even perfectly strong and sound cement will start to develop cracks between the cement and the ridgecapping over time. This is an ideal situation for the products that are out on the market now. These ‘flexible pointing’s’ which are widely by roofing contractors used are designed to be pushed into these cracks. The flexible pointing ‘bites’ into the cracks of the cement and forms a very strong bond over your ridgecapping and roof tiles. It is also a very good idea to make sure the collar of ridgecapping has flexible pointing installed to them. The ‘collar’ of the ridgecapping is the area of the front of the ridge that overlaps the last ridgecapping. Installing collars to these are vital in prolonging your pointing and re-bedding.
Re-bedding or Bedding is basically the first step taken in a roof repair to ensure that your ridgecapping, valleys, gable ends or barge capping are secure on the roof and run in a nice straight line. A cement mix of about four parts cement and one part sand needs to be combined and turned into an easily manageable mix. A bedding trowel is then used to lay long, thin scoops of cement in which the ridge tile or roof tiles can be pushed on to and formed into place. A novice will need to use a bedding frame to guide them in making sure they keep the cement running in straight lines. A more experienced tradesman will be able to bed the cement down easily without this aid.
Care needs to be taken to make sure that the bedding frame and all tools used are washed thoroughly after use. Cement sets rocks hard and often will not be able to be cleaned off surfaces without the use of a grinder.
On many occasions, a complete roof restoration which involves pressure cleaning and painting and ridge works (if the cement is in sound condition) will not require re- bedding. Strong cement will have had years to harden and shift into position, holding the tiles and ridgecapping firm. Disturbing the formed cement in this case is not warranted and just an extra cost that is not necessary. The only exception to the above is where you have a roofing valley. Over time, roof valleys accumulate dirt and debris behind the cement. This eventually will block the correct flow of water and cause a very annoying that cannot be seen until the valet cement is removed. It is this reason that we remove all valley cement with every job we do as a matter of roof maintenance. We know that eventually it will need to be done so the best time to do it is when other work is being done to the roof.
Once the cement hardens up, it is then time for the roof pointing to be carried out. Pointing is the step that follows the re-bedding process and bonds everything together. There are many forms of pointing available on the market. There are cement based pointing’s and there flexible based compounds. Cement based Flexipointing is not widely used anymore and not recommended for roofing. A flexible pointing is a better product and is suited for roofing structures as they contract with the weather.
Cement is a very robust roofing material and has been used for many hundreds of years. A strong mix of cement and a neat, original roofing installation job will ensure that minimal re-bedding will be required for a long time. Remember that not all roofs necessarily need re-bedding. If they do require re-bedding however, it is important to have the job done properly. The most imperative thing is to ensure you get the right advice.