Why is this garage roof leaking?

[plummet]

Hi

I have a 1980s garage with a corrugated cement asbestos roof. The roof looks to be in good shape to me from the inside, but there are significant leaks coming from where the sheets overlap.

I can't figure out why as there are no obvious cracks. I am wondering though whether the moss on the roof might be causing it, e.g. allowing water time to soak through, or causing it to wick upwards? Could also be the washers around the bolts (which mostly seem cracked) although the water isn't obviously coming it from anywhere close to those?

Any ideas appreciated - thanks.

 

[blup]

What you say, especially the bolts, plus general deterioration.

Blup

 

[plummet]

What you say, especially the bolts, plus general deterioration.

Blup

Thanks - maybe I'll see if I can find one to clean/repair it. I did get a quote to have it replaced but it was nearly £2500..

 

[noseall]

I did get a quote to have it replaced but it was nearly £2500..

Did you snatch his hand off?

 

[hllns]

I've a shed with the same sort of panels, generous moss growth was causing water to obviously backup in the valleys over the join which didn't look ideal to me so I tried to clear them out a bit, any backup when it's raining?

 

[DiyNutJob]

Since the higher point is wet, I would say the roofing material is worn out.

 

[plummet]

I've a shed with the same sort of panels, generous moss growth was causing water to obviously backup in the valleys over the join which didn't look ideal to me so I tried to clear them out a bit, any backup when it's raining?

Good question, I'll try to check but reluctant to clamber on it!