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  • The Cost of Repairing Roof Joists

    The average UK cost of repairing and replacing damaged roof joists..

    The Cost of Repairing Roof Joists



    Roof joists are structural beams that are typically made from wood. These beams usually run horizontally, connecting opposing walls and supporting the roof above. Over time, it is not uncommon for roof joists to become weathered and rotten and require replacing. In order to withstand the weight of the roof, timbers, and coverings, it is essential to maintain a good standard of structure. In the UK, the average cost of repairing roof joists of a 3-bedroom home starts around £250-£500 per beam. In most cases, you would require the assistance of a roofing specialist or professional carpenter to either repair damaged joists or completely renew the entire roof. Today we will help you understand everything you need to know about roof joists and all of the things to consider associated with repairing or replacing them.

    There are many things that can lead to the failure of your roof joists, but, commonly, the most significant threat is water. If your property is suffering from repeatedly penetrating damp or a leak, wooden roof joists will inevitably become rotten. It is essential to get areas that could potentially be suffering from water damage inspected by a structural professional. If you find that your property has damaged roof joists, this can lead to severe problems that require immediate attention. Rotten roof joists can develop into sagging roofs and ceilings, overloaded areas, and rotting of the adjoining structure. Before you attempt making any repairs, you should first be certain that you have identified the source of the problem correctly, in order to plan an appropriate course of action. Carrying out the improper treatment of rotten or damaged roof joists can be costly and lead to future complications in your property. Your professional roofer or structural engineer will most likely offer one of three options. The options for replacing roof joists are the repair of the beam with timber resin materials, repairing using specialist repair plates, or where extensive damage is present, the removal and replacement of the entire joist and truss.

    Typical prices

    Job Description Duration Material Cost Labour Cost
    Repairing a Wooden Roof Joist 1-2 Days £100-£250 £150-£200 Per Day
    Repairing a Joist with Metal 1-2 Days £250-£400 £150-£200 Per Day
    Replacing an Entire Roof 3-5 Days £2000-£3000 £150-£200 Per Day

    Things to Consider

    There are many things you should consider before attempting to replace or repair a roof joist in your home. Firstly, after identifying the problem, you should consider eliminating the source of the damage before carrying out any treatment to the beams themselves. This way, you will eradicate any chances of future destruction and better understand how to maintain the quality of your roof. You will also need to consider the method of treatment you plan to carry out. As we mentioned earlier, there are three main procedures of replacing or repairing damaged roof joists, and your professional tradesperson will be able to advise you on the best solution for your problem. There will likely be a lot of noise pollution during the restoration of your roof joists. As with any other major home improvement project, the work can often cause short-term disruption to your day to day life.

    Consider how you prepare and manage to live in what can sometimes feel like a construction site while the work is being carried out. We always recommend shopping around before hiring a professional tradesperson to carry out work within your home. As with any other service, various contractors will quote different prices for the job, so in order to get the best price, be sure to gain multiple opinions. If you are considering carrying out the repair yourself, you must acknowledge the seriousness of a faulty or unsupported roof. Remember, carrying out improper or inadequate quality repairs can often lead to costly and more extensive work in order to resolve the issues. By gaining professional advice, you reduce the chances of having to pay unnecessary costs and running into surprise complications. More often than not, damages to roof joists rarely stop at the signs of surface damage. You may run into a collection of nasty surprises, so always consider setting money aside to cover unexpected costs.

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    Repairing Roof Joists Yourself

    While it is not entirely impossible to take on a DIY roof joist repair, replacing or repairing a damaged roof joist is a complicated procedure that requires precision. Rotten roof joists are a severe problem and commonly lead to underlying issues and damage to opposing structures. While you may be able to see the damaged or rotted wood visibly, there will also likely be damage that you cannot see. In order to successfully repair a roof joist, the work must be carried out correctly using proper techniques and suitable materials.

    If you're going to attempt a roofing job yourself you need to ensure you use the correct equipment for the job. Roofing joists are very heavy and it's strongly advised that you don't attempt to move them alone. Any accidents can not only be dangerous but can also lead to costly repairs and damages to your property, so never attempt the installation or repair if you are unsure about anything.

    For this example, we will be demonstrating a brief step-by-step guide on how to repair a wooden roof joist using timber materials.

    Step 1 - Remove any visible rotten wood with a chisel. The wood should come away quite easily, without much force.

    Step 2 - Determine the extent and area that you intend to repair or replace. Measure the length of wood required for the space. If only part of the joist is damaged, measure the space where the rotten wood has been removed.

    Step 3 - Cut the timber to the desired size and screw into place. If you are replacing the entire joist, you may screw the wood into the opposing top and bottom joists.

    Step 4 - Seal the wood with a specially designed waterproof sealant. This will prevent future damage and reduce the risk of having to repair your roof again. Most sealants are available at your local hardware stores and can be applied to the wood using a paintbrush.

    Step 5 - Inspect your loft and ceiling for signs of further damage. Treat any areas where water may be accessing the property. We always advise seeking the recommendations and advice of a professional carpenter to reduce the risk of additional roof problems.

    Repairing Roof Joists Checklist

    • Thoroughly inspect your roof for signs of damage. Check for sagging and darker areas in the property’s exterior.
    • Identify the extent of the damage and source, for example, water damage due to exposure.
    • Treat the source of the problem to diminish any future complications with the structure of your roof.
    • Contact multiple tradespeople for advice, requesting a call out if possible.
    • Shop around, comparing multiple quotes from various professionals to source the best price possible.
    • Remember to compare the best methods and materials available on the market to find the most cost-effective solution.
    • Ask for information and advice on how to properly maintain and care for your new roof joists.


    How long does a roof replacement take?
    On average, an entire roof replacement on a regular-sized family home should take no longer than 3-5 days to complete. This timeframe will vary depending on the scale of your project and should be used as a guide only.
    Do I have to be home during a roof replacement?
    The simple answer is, no. You don't have to be home while the contractors carry out the repairs to your roof joists.
    Is repairing roof joists complicated?
    This answer will depend on the level of damage your roof has endured, and the extent of the repair needed. In some cases, a simple patch-up using quality materials will be sufficient. In others, a full roof restoration may be necessary.
    What are the warning signs of a damaged roof?
    You may find that your roof is visibly sagging or showing signs of dark, dirty areas. This can sometimes indicate that water has entered the structure and caused stress on the supporting joists. You might also notice several exposed areas where tiles may be missing.
    Do I need planning permission to repair or replace my roof joists?
    No, you do not usually require building regulations or planning permission to repair or replace your roof. You may, however, request planning permission for alterations to the design and shape of your roof. Contact your local authorities for more information.
    What causes damage to roof joists?
    The common culprit for roof damage is generally water. However, joists may fail as a result of excessive weight on the roof or damage from fallen trees and other objects.
    What is the most reliable repair for a roof joist?
    While wooden beams have been used to repair and replace roof joists for decades, the most reliable material to use would be metal plates. Your expert tradesperson will talk you through the available methods of repair for your property.
    Last updated by MyJobQuote on 14th November 2019.

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