5 Common Problems with Thatched Roofs

We have picked out five of the most common problems which cause a thatch roof to leak and outlined the best way to solve them. If you're having problems and your thatch roof is leaking, read on!

Problem 1. Leaking Capping

Symptoms: The capping (or ridging) is the section right at the top of the thatch roof. Sometimes a leak will come directly from the top of the roof and other times the water will trickle down the internal poles and make it seem as though the leak is from elsewhere on the roof - for this reason it is sometimes difficult to tell whether the leak is coming from the capping.
The Problem: Traditionally the capping is made out of a mix of cement, sand and crusher dust which forms a rigid capping. Because of the long, thin shape and expanse of the capping and the nature of the cement mix, cracking is almost guaranteed if expansion joints have not been fitted. Some thatchers fit a thin layer of plastic under the capping before the cement is laid although often this layer is punctured during the laying process and the plastic is therefore ineffective.

Cracked Capping

A capping in bad condition

Solution: Once the capping is laid it can be covered with a membrane and water-proofing solution. This layer water-proofs the capping and allows movement and flexibility as the cement base ages. The membrane and solution must be fitted according to the manufactures specifications to be effective. This solution can be costly (and certainly costs more than fitting a cement capping alone) but over time it is the most effective solution to capping problems as you will not have to call out a thatcher to repair the capping every year or so.

A layer of membrane being added to the capping

A newly repaired capping

Problem 2. Leaking Valleys

Symptoms: The thatch roof is leaking where two sections of roof meet from different angles (the valley section).
The Problem: Generally valley sections, even if not fitted correctly, are fine when the roof is first thatched. After a few years of rain and damp conditions however, problems start to arise. Valley sections bear the brunt of the water drainage for thatch roofs and experience a large amount of water flowing down them when it rains. They take longer to dry out than other sections of roof because of their angle and thickness and they therefore rot more quickly allowing leaks to form.

An inadequate, rotting valley

Solution: A proper valley "section" needs to be fitted to help the water drain form the roof quickly and prevent the thatch in that area from holding water and retaining damp. These valley sections can be fitted to existing roofs, the process involves stripping that small section of valley and fitting the valley section with thatch around it.

A valley with a valley section fitted allowing
drainage

Problem 3. Leaking or wind damaged Corners

Symptoms: The thatch roof is leaking at the corner or the thatch has been " lifted" by the wind and is falling out.
The Problem: Corners are commonly a problem for inexperienced thatchers as they are a difficult area of the roof to thatch. They are often therefore thatched too thin or with too little compaction.

A corner very thinly thatched

Solution: The corners of the roof need to be stripped and re-thatched. If you are in a high wind area hex-net can also be applied to the corner of the roof to prevent the wind from buffeting the thatch. This general problem is easily prevented by using an experienced thatching contractor.

The same corner re-thatched and covered with
hex-net

Problem 4. Inadequate Compaction of Thatch

Symptoms: Accelerated rotting of the thatch, thatch coming out of the capping, regular wind damage and generally endless problems with the thatch leaking.
The Problem: This problem is connected with all of the problems mentioned above and many others besides!  Inexperienced thatchers and thatchers who rush jobs do not compact the thatch properly on the roof. This causes endless problems and also puts your thatch at an increased risk of fire due to the extra oxygen in between the thatch stalks. The thatch MUST be applied to the compaction of 35 - 50 kg per square meter.

A roof with poor compaction

Solution: This is a very difficult problem to deal with and all depends on the quality and condition of the twines used to tie the thatch. If the twines are in good condition then the entire roof can be re-tension-ed and brushed to re-compact it. If the twines are in poor condition or are of poor quality then they will snap as soon as you pull them - in this case the only way to end your problems is to re-thatch the roof to adequate compaction.

Twines being re-tension-ed

The roof after re-compaction

Problem 5. Animal & Bird Damage

Symptoms: Thatch hanging out of the roof and small leaks.
The Problem: Thatch does not fare well in the face of birds and animals. In some instances where dealing with animals like baboons and monkey the damages caused are almost malicious - the animals will physically pull the thatch out of the roof. If your roof is badly compacted in the first place these damages will be exaggerated as the thatch comes loose more easily.
Solution: Whether the bird and animal damage is bad over the entire roof or only over sections, hex-net can be fitted to prevent a lot of damage. It is also important to keep trees pruned well back from the roof to prevent animals having such easy access to the roof or using it as a thorough-fair from A to B.

Hex-net fitted to the roof to protect from animal
damage

It is important to always call an experienced thatching contractor to help identify the cause of leaking thatch roofs and prepare a satisfactory long-term solution. To read more about thatched roof maintenance visit our website.