Can I Put a New Roof Felt Over the Old One?

John McEvoy
October 2, 2023

If you're wondering whether it's possible to lay new roof felt over your existing one, you're not alone. Many Irish homeowners are opting for this method due to its cost-effectiveness and ease.

This article clear the pros and cons of overlaying a new felt on top of the old, whilst highlighting key points to consider before making that decision as well as some practical alternatives in case it doesn't fit your needs.

Key Takeaways

  • Putting new roof felt over the old one can save time and money, but it has pros and cons.
  • Factors to consider include the condition of the existing felt, weight issues, and future plans for your roof.
  • Alternatives to overlaying new felt include installing new roofing materials or repairing the existing felt.
  • Seeking professional advice is recommended to make an informed decision about your roof.

Can You Put a New Roof Felt Over the Old One?

Putting new roof felt over the old one can have both pros and cons, and there are several factors that should be considered before making a decision.

Pros and cons of putting new felt over old felt

Putting new felt over old felt has both good and bad sides. One good thing is that it saves time and money. You don't have to take off the old felt. This means less work for you or for the workers if you hire them.

Another plus point is extra protection. The old felt stays there under the new one, making your roof even stronger against rain, snow and wind.

But there are also downsides to this method. The first con is weight issues which can harm your house frame with time. Second, hiding problems might be another risk as troubled spots of previous layer could stay unnoticed leading to future damage.

Factors to consider before making a decision

Before deciding whether to put a new roof felt over the old one, there are some important factors to consider. First, you need to assess the condition of the existing felt. If it is in good shape with no leaks or damage, overlaying a new layer may be an option.

However, if the old felt is worn out or has significant issues, removing it and starting fresh might be necessary for better insulation and protection.

Another factor to consider is the weight of multiple layers of felt on your roof deck. Adding another layer can put extra stress on your structure and may require additional support.

Additionally, take into account any regulations or guidelines in your area regarding multiple layers of roofing materials.

Lastly, think about future plans for your roof. If you're considering other roofing options down the line or anticipate major changes like a loft conversion, it might be best to remove the old felt now rather than later.

How to Re-felt a Shed Roof?

To re-felt a shed roof, start by removing the old felt and nails from the roof. Prepare the roof timber by ensuring it is clean and free of any debris. Next, lay new felt on a ridged roof, making sure to overlap each layer for maximum protection against moisture.

For flat or pent shed roofs, replace the felt by applying a new layer directly over the existing one. Remember to use appropriate materials and techniques for proper installation.

Removing the old felt and nails

To remove the old felt and nails from your shed roof, start by carefully pulling up each strip of old felt using a pry bar or scraper tool. Be sure to remove any nails or staples that are holding the felt in place.

Take your time to avoid damaging the underlying roof deck. Once all of the old felt is removed, clean off any debris or dirt from the roof surface before proceeding with the installation of new felt.

This step is important for ensuring a smooth and secure bond between the new felt and the roof deck.

Preparing the roof timber

To prepare the roof timber for re-felting, start by removing any old nails or staples from the timber using a claw hammer or pry bar. Make sure the timber is clean and free from debris before applying new felt.

Inspect the timbers for any signs of damage or rot, and make necessary repairs or replacements as needed. It's important to ensure that the roof deck is in good condition before laying down new felt to prevent any future problems.

Laying new felt on a ridged roof

To lay new felt on a ridged roof, you will need to start by removing the old felt and any nails that are sticking out. Make sure to prepare the roof timber by cleaning it thoroughly and repairing any damage.

Then, you can apply the new felt by unrolling it onto the roof and securing it with nails or staples. It's important to overlap each piece of felt to ensure proper waterproofing. Once all the felt is in place, you can trim off any excess material and make sure everything is securely fastened down.

This process will give your ridged roof a fresh layer of protection against the elements.

Replacing felt on a flat or pent shed roof

To replace the felt on a flat or pent shed roof, you need to start by removing the old felt and any nails. Then, prepare the roof timber by making sure it's clean and in good condition.

Next, lay the new felt over the roof, making sure it overlaps at least 75mm (3 inches) with each layer. You can use adhesive or nails to secure the felt in place. Finally, trim off any excess felt and ensure all edges are sealed properly for added protection against water leaks.

It's a straightforward process that you can do yourself for extra savings!

Alternatives to Putting New Felt Over Old Felt

If you're not sure about putting new felt over the old one, there are alternatives to consider. From installing new roofing materials to seeking professional advice, explore your options before making a decision.

Read on to find out more.

Installing new roofing materials

If you're thinking about installing new roofing materials, there are a few things to consider. First, it's important to choose the right type of material for your specific needs and budget.

There are various options available, such as shingles or a roofing membrane. Next, you'll need to make sure that the existing roof is in good condition and can support the weight of the new materials.

It may also be necessary to remove any old layers of roofing material before installing the new one. Lastly, it's recommended to seek professional advice if you're unsure about how to properly install the new roof or if there are any complex issues involved.

Repairing the existing felt

If you have concerns about putting new felt over your old one, repairing the existing felt might be a good option. This can help extend the life of your roof and save you money. To repair the felt, start by cleaning any debris or dirt from the surface.

Then, use a patching compound to fill in any cracks or holes in the existing felt. Make sure to smooth out the patch so it blends with the rest of the roof. Finally, apply a coat of roof sealant over the repaired area for added protection against leaks and damage.

It's important to regularly check and repair any damaged areas to ensure your roof stays in good condition for years to come.

Seeking professional advice

If you're unsure about whether to put new roof felt over the old one or not, it's a good idea to seek professional advice. A roofing contractor can assess the condition of your current roof and provide recommendations based on their expertise.

They will consider factors like the age of the existing felt, any damage or leaks present, and the overall structure of your roof. By consulting with a professional, you can make an informed decision that ensures the long-term safety and integrity of your home.


In conclusion, while it is possible to put a new roof felt over the old one, there are pros and cons to consider. It may provide extra protection and save time, but it can also cause problems if the existing felt is damaged or if moisture gets trapped between the layers.

So, before making a decision, it's important to assess the condition of your roof and seek professional advice if needed.

Contact us today!

HP Roofing is a team of residential & commercial roofing contractors in Dublin for all your needs. We offer a wide range of roofing services, from roof repairs to roof replacements.
Call HP Roofing 01 453 3366

Frequently Asked Questions

Can I put a new roof felt over the old one?

Yes, you can! You can install new roofing felt over an existing one as part of your DIY roofing repairs or during a loft conversion roof felt replacement.

Do I need to remove the old roof before applying a new one?

It's not always necessary to tear off and remove the old roofing felt. But remember, if you are installing a whole new roofing system, removing the old one might be best.

What do I need to consider when overlaying felt on my flat roof?

When adding two layers of felt on your shed roof or flat roof, make sure to re-nail the old deck properly before installing the roll roofing.

Is it okay for Roofing contractors to put a new shed roof felt replacement over my existing shingles?

Yes! In some cases in the roofing industry, installing a new layer without removing previous shingles is acceptable.

Does putting newer tiles require any special techniques?

Applying a modern style requires proper knowledge about standard practices used by expert workers from across numerous fields dedicated towards making roofs better.

How often should I inspect or replace my roof felt?

Regular inspections every 1-2 years are recommended. Depending on the material and local conditions, roof felt typically lasts 15-25 years, but it's wise to monitor and replace as needed for optimal protection.

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*FYI, parts of this blog post were drafted by artificial technlogy. But rest assured, it's been thoroughly researched, edited, reviewed and me & my team.
Founder @ HPRoofing

The founder of HP Roofing, with years of industry experience, providing top-notch roofing services for residential and commercial properties in Dublin, delivering high-quality roofing solutions that combine both aesthetic appeal and durable functionality.