head lap on slate roof

[measuretwice12]

ou
Sun 19/01/2025 08:00


Got a 5 year old natural slate roof (new build). I have a couple of raised and cracked tiles and in one area two slate tiles have come off in high winds. I have now discovered that the headlap (which should be minimum 75mm for the pitch) is only about 40mm on average and down to about 20mm in some areas. The roofer is happy to replace the mentioned slates, will this fix the problem???, from what I have read, absolutely not!!! Keen to hear your thoughts on this!

 

[jj4091]

Not in the roofing trade but sounds like it might be a job for the NHBC to sort out.

 

[measuretwice12]

I agree, I need to get the warranty provider involved. This is my concern:

"There are few details on a slate roof installation that, if done wrong, will cause the entire roof to be condemned and have to be removed and done all over again. Headlap is one of them".

Traditional Roofing Magazine Issue #6 - Understanding Headlap on Slate Roofs

JOSEPH JENKINS (world renowned slate roof expert)

 

[robinbanks]

down to about 20mm in some areas

Jeez, their batten spacing must be all over the shop or slates with mixed sizes/gauges were installed??

Not sure how either of those happens in a world where tape measures are a thing

If the headlap of every slate is too low, the roof needs re-laying with the battens closer together, which also involves re-holing every slate to match.

 

[jj4091]

I agree, I need to get the warranty provider involved. This is my concern:

"There are few details on a slate roof installation that, if done wrong, will cause the entire roof to be condemned and have to be removed and done all over again. Headlap is one of them".

Traditional Roofing Magazine Issue #6 - Understanding Headlap on Slate Roofs

JOSEPH JENKINS (world renowned slate roof expert)

I don't know how he can say that when you have seen the results of poor lapping. You need an independant experts opinion, perhaps before you approach NHBC preferably in writing.

 

[measuretwice12]

Update on the issue with poor headlap. I have had an independent survey done, which recommended replacing the entire roof cover due to the poor headlap and general issues with workmanship, numerous lifted and cracked tiles were found. The warranty provider (not NHBC), are not willing to replace the roof as they are NOT required to rectify the defect as long as it is possible to provide a lasting and effective repair of the damage. What solutions are are available to fix the damage when the headlap is only about 35- 40mm on average and down to about 20mm in some areas (headlap should be minimum 75mm for the pitch). I would really like to hear the forums opinion on this.