How to Fix a Roof Leak (From the Inside)

Fixing a roof leak from the inside, (in the loft or attic) is a far easier task than having to climb on a roof to fix it. Climbing on the roof can be inherently dangerous. Even a fall from a single story building can give you a nasty injury; or much worse….

Inside Roof Repair – How to Fix a Roof Leak (From the Inside).

Go straight to the repair…

Where is the Roof Leak?

Finding a roof leak should be straight forward, as it’s usually identified by a wet patch somewhere. Gravity would normally have a hand in indicating where a leak may have come from.

But, water doesn’t always go straight down. It can soak into things, so a wet patch may never appear. Damage may be caused by the mere presence of the water soaking into roof timbers, causing rot, decay and other issues.

The Roof Showing Water Ingress (No Drips, Underlay Fitted)
The Roof Showing Water Ingress (No Drips, and an Underlay is Fitted).
The leak in the image above needs an external repair. Crow’s have chipped away at the concrete used to fix the ridge tiles, allowing water to soak through the roof, when there is prolonged rain.

Water can also track away from the source of the leak, and then fall to the ground. This can give a false idea of where the leak originated.

How to Find the Roof Leak?

It sounds obvious, but finding a roof leak is best done when it’s raining… You can still find a leak on a dry day, (looking for stains and water damage). But, you may not find the source of the leak if the water is tracking across the roof. You usually need to find the highest point where water has entered.

Wind has a horrible habit of making leaks appear where they’ve never been seen before! Plus some leaks only appear when there is sufficient wind speed, a specific wind direction and the correct volume of water. Wind blown rain can produce ‘one off’ leaks too!

Damage Caused by a leaking Roof Causing the Timber to Rot Away.
This is where a chimney used to be, (but has since been removed). The lead flashing around the original old chimney must have been defective.

Hopefully you’ll have an easily identifiable leak. Then a repair of the roof can commence. Otherwise it’s a waiting game for a day when the wind speed and rain are blowing in the right direction…

The aim is to trace the leak to its highest point, which would usually indicate that the source is nearby.

What can Cause the Roof Leak?

There can be a number of causes:

A Slate Roof (the Underside From the Loft or Attic).

Old Age, Wear & Tear:

One of those things, it just happens…

Expansion & Contraction:

Roofs can get very hot and cold over the different seasons. Some materials such as lead flashing can expand and contract a fair amount. If this movement is restricted (sometimes caused by over nailing, or nailing in the wrong place, etc), the material can crack letting in water. This process can happen with other materials on the roof, lead is just a good example.


Things can hit your roof. Branches, stones, balls, general windblown debris, (…and hopefully no aeroplane or satellite parts!). All can have an effect, making holes, dislodging or loosening.


I like birds, but they can do damage to your roof… Unfortunately my next door neighbor loves to feed crows and seagulls. The worst it got was when there was over 200+ crows and over 45+ seagulls. All at once, in one big food fight.

The issue is… The crows will hang around on our roof, waiting to be fed. They get bored. This is when they start attacking the roof. Their beaks are like little pointed hammers, chipping away looking for bugs! Normally crows aren’t a problem, but whilst they’re waiting to be fed, boredom sets in. You can hear little bits that have broken off, rolling down the roof!

Birds also love to nest, so they may make a hole or two whilst searching for the perfect nesting spot.


The wear & tear and expansion & contraction issues are often caused by the weather.

Material Failure:

When built, parts of the roof may not have been installed correctly. Lead flashing may not have been installed correctly, or there has been a component failure. For example, a defect in the lead sheet, a cracked slate, roof tile, etc.

When a Roof Leak Isn’t a Roof Leak:

There are occasions when you get condensation on the inside of a roof. This is when there is a temperature difference between the inside and outside and condensation can form on the underside of the roof.

Slate Roof – The Underside Showing Condensation on a Cold Day.

This is nothing to worry about, as long as you have good ventilation in your roof. There must be a good airflow. This will allow the moisture to evaporate and for the roof to quickly dry out.


If you have a roof underlay installed and it is in good condition, then you shouldn’t suffer from any leaks, This is as long as there’s no huge great gaping hole in the roof and the underlay is in good condition.

What is a Roof Underlay for?

Water can sometimes get past the roof covering. This usually occurs when there’s a strong wind (and it’s blowing in the wrong direction). The wind can force the water under the slates or tiles and through any gaps. These type of leaks are usually small and are often random. The underlay directs any of these small leaks away into an external gutter.

A Slate Roof – No Underlay (You can see the Roof Covering & the Roof Battens).
A Slate Roof (With an Underlay Fitted).

Inside Roof Repair – How can I Fix the Roof Leak?

Faults should be fixed using the correct method. If a part needs to be replaced, it should be replaced with the correct replacement. However:

  • There are times when a temporary repair may be needed.
  • Or a different type of repair, is just as good, (and actually may be just as effective and long lasting).

This article describes how to make a repair from the inside of the roof. This should be a much cheaper, easier and safer method…

Slate Roof (a Broken Slate). This appears to be a man made defect, as it has a clean dead straight break, with a gap rather than a fracture line.


  • Safe access to the underside of the roof.
  • Finding the source of the leak.
  • The area where the water has been entering, isn’t huge and not doomed to failure…


For this type of repair:

  • Polyurethane glue.


  • Cleaning tools.
  • Small pieces of wood, or stiff cardboard.
  • Gloves.
  • Safety glasses.
  • An appropriate dust mask, (protection against glue vapours if needed – Please read the safety data sheet).
  • Roof coverings may have an under layer (an underlay). These coverings are installed to protect against small leaks (wind blown), and can direct water out of the roof area into a gutter. The underlay can deteriorate over time and can fail. Older houses, don’t often have an underlay fitted, unless the roof has been replaced.
  • Polyurethane glue can be used when the surface is wet. This is very handy!

Roof Repair (from the inside):

  1. Identify where the leak enters through the roof.
  2. Read the safety instructions on the polyurethane glue container. Wear the appropriate safety equipment.
  3. Once identified, clean the area to get rid of debris, cobwebs & dust. This will ensure a good bond with the Polyurethane. Note: Polyurethane glue can be used when the surface is wet.
  4. Dependant on the access available, squeeze the polyurethane into the hole or crack. If this is not possible, use a piece of wood, or stiff cardboard as a makeshift spatula to work the polyurethane into the hole or crack.
  5. Gravity will want to let the polyurethane fall or run out of the crack. Don’t let it fall out. Keep working it back into the hole.
  6. Polyurethane expands, (a bit like expanding foam) over time. 15 to 20 minutes later, the polyurethane will start to harden and expand slightly. Note: You can get faster curing Polyurethane glue.
  7. Eventually, the hole or crack will become blocked and you will no longer have to work the polyurethane into the hole.
  8. As long as the hole is fully covered, the hole in the roof should be sealed.

How to Fix a Roof Leak (From the Inside): This takes you back to the top of the page…

  • Do not try to fill every gap. The roof is meant to breathe and be able to expand and contract. Sticking everything together may cause further issues later on. I.e. Only repair the leak.
    • I.e. Only repair the leak.
    • Don’t use expanding foam. This may expand far more than needed and could cause issues later on.
  • If the leak is behind a large beam or covering, you may not be able to gain access to do the repair.

Ordering Tools & Materials:

The following table gives examples of the glue, gloves and vapour mask you can buy to fix your roof. If you’re not sure what you need, sometime it’s worth having a look? The list below may give you an idea of what’s what’s available, what to look for and how much it costs…

Ordering Materials – Examples of What You Can Buy:

Leaking Roof
Item Location
Polyurethane Glue  UK Prices
 US Prices
Gloves  UK Prices
 US Prices
Vapour Mask
Vapor Mask
 UK Prices
 US Prices
Disclosure: The links in this table are “affiliate links” This means we may garner a small commission (at no cost to you), if you choose to make a purchase.
Thank you for your support.

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