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How To Repair An Old Felt Roof

Locating your Leak

If you have to repair an old felt roof, there are a few options to choose from.  First of all you need to locate exactly where in the roof the leak is coming from.  You may be able to trace the leak path by examining the room underneath your flat roof.  Obvious signs will be dripping water or damp patches.  If you struggle to trace the leak as the patches have dried, you may have to examine your ceiling whilst it rains next time.

Another way of examining your flat roof for a leak path is to get on top of it.  Only do this if your flat roof is strong enough to hold your weight.  If it has been leaking for some time, the roof timbers may have become rotten in areas.  Check the overall condition of your felt.  Signs of wear include tears, rips, holes and delamination.

Repair an Old Felt Roof

Once you have found the spot in your flat roof where your leak is coming, you need to decide how severe it is.  Flat roof repairs usually fall into one of the categories below.

1.  Temporary Repair

This type of repair depends how much life you think your flat roof has.  Temporary repairs are ideal when you are close to replacing your whole roof.  For example, if you think your roof has less than 2 years left, it may be worth doing a cheap temporary repair until you can afford to replace the whole lot.  Short term repairs are quick and easy.  You could even do it yourself.

If you have a split in your felt, carefully remove the gravel around it.  Cut a piece of new felt to use as a patch to cover the split.  Stick this felt over your split using bitumen adhesive, ensuring there if a 50mm overlap beyond the split.  Then you will need to apply some bitumen adhesive over the split repair.  Ensure the edges of your patch are sealed with bitumen adhesive.

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2.  Permanent Repair

Permanent repairs are ideal when the rest of your felt roof is in good condition, with more than 2 years of life left.  This type of repair will ensure your felt will see out the remaining life of the roof.  We recommend you seek a hot felt roofing contractor for a more permanent repair.  They will have the necessary tools and equipment to do a reliable job.

3.  Replacing All of your Roofing Felt

If you need to repair an old felt roof, then you may consider getting it completely replaced for a new one.  Usually this is done if the overall condition of your roof is very bad.  If most of the roofing felt looks very degraded, it could be a waste of time repairing the leaking parts, as other area will create a problem no long after your repair. You can view this full guide on how to replace a felt roof the professional way.

how to repair an old felt roof

How Long Do Felt Roofs Last

Roofing felt is one of the most common and oldest techniques when it comes to waterproofing flat roofs.  The technology has advanced a lot over the years.  The most reliable types of felt are touched on.

Roofing felt usually is made up of a fibre material which is coated with bitumen, and a layer of gravel.  Torch on felt has a 3 layer system, requiring two levels of underlay underneath the cap sheet.

You will notice that felt roof have a layer of gravel on top.  This helps to absorb and reflect heat away from the felt, helping to prevent cracking and blistering.  The life span of roofing felt is dramatically decreased if the gravel of the felt is removed, or animals such as cats and foxes scratch it.

A hot felt roof that is well looked after should last up to 25 years.


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Posted on 17th July 2019 at 2:09 pm


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