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How Much Does It Cost To Replace Roof Felt Under Roof Slates Or Tiles?

Updated: Aug 3, 2023

Roof felt is a barrier beneath roof tiles to prevent weather damage and provide adequate insulation. An intact roof is vital to keep water out of your home and help withstand winds and storms.

However, although roof felt has a long lifespan, it will inevitably deteriorate over time. If you believe your roof felt requires replacement, you’ll need to know how much it costs to do the necessary work.

Roof Felt – What Is It?

Sometimes called roofing underlay, roof felt is a protective barrier that keeps your roof watertight. Usually made from cellulose, wood, polyester or fibreglass base with an asphalt coating, roof felt guards against exposure to bright sunlight or extreme cold.

Modern roof felt can last about 30 years and is suitable for use on pitched roofs while also vital for a flat roof. In most cases, homeowners remain unaware of a problem with their roof felt until they experience a roof leak.

Once this occurs, it’s imperative to seek repair as quickly as possible to prevent long-standing problems.

What Will It Cost On Average To Replace Roof Felt?

Although it’s possible only to replace a small patch or two of roof felt, replacing the entire supposed to prolong your roof’s lifespan and guard against further property damage is often advisable.

It will cost about €200 if only a patch repair is being carried out, but a complete professional roof re-felt starts from around €750 but can be higher depending on your requirements and the size of your roof.

How Does The Re-Felting Process Work?

The process of roof re-felting is as follows:

1. Scaffolding must be erected to allow access to the roof.

2. The existing tiles or slates are removed, discarded, or put carefully away for re-use.

3. The existing felt is removed.

4. Any rotten roof timbers are replaced.

5. A breathable membrane will be nailed to the rafters.

6. Battens will be fixed over the membrane.

7. The tiles or slates are refixed to the roof and secured with the battens.

8. New flashing is fitted around roof features and chimney stacks.

Which Factors Affect Roof Felt Replacement Costs?

Several factors could impact the cost of your roof felt replacement, including:

• Any hidden damage to the roof or underlay that requires additional work.

• Battens – New battens have to be added during a felt replacement which causes the cost to increase.

• Felt – The price of the roof felt will vary depending on the quality and type of material chosen.

• Tiles – replacing all the roof tiles when changing the roof felt may be advisable.

• Scaffolding – Scaffolding must be erected to complete the job and then dismantled when it is complete.

• Skip hire – When felt and tiles are being replaced, hiring a skip and paying for waste disposal may be necessary.

• Insulation – If you have cold loft insulation, a replacement will not be required, but if you upgrade to a warm loft insulation option, you will need to pay more.


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