The Importance of Correct Leadwork

[Flyfisher]

I'm finally repairing an outbuilding roof that has been suffering from many years of neglect (including, I'm sorry to say about 4 years of mine - though I did have higher priorities such as the main house roof) and today uncovered a masterclass in poor leadwork.

The first photo shows the valley in question, stripped of all the tiles and battens. The middle length of lead is about 2m, well over the maximum of 1.5m recommendation in my Lead Sheet Association handbook. I'm pretty sure the consequence of this has been the two splits shown in the second photo (due to many heating/cooling cycles). You can also just about see the blackish marks around the splits that was some previously useless attempt at sealing the splits with some sort of tar or mastic - doomed to failure because of heating/cooling cycles re-opening the splits.

The predictable result has been years of rainwater ingress nicely funnelled onto the valley boards (3rd photo) and the structural valley rafter - somewhat conspicuous by it's absence from the 4th photo (next post) after having completely rotted away!

Fortunately, the purlins on each side of the valley have been unaffected and have provided the necessary support to prevent this entire section of roof from collapsing. So, it looks like I've caught the problem before too much damage has been done and the required repairs should be fairly straightforward.
Hopefully.

 

[Flyfisher]

 

[MdB]

Problems like this are very useful to see. It gives you one hell of an incentive to get it right when doing a similar job yourself. Thanks for posting.

 

[Flyfisher]

The other interesting thing (am I really getting this geeky? :wink: ) is that other areas of the roof have been far less affected by leaks where the water has just dripped through, run off the rafters onto the floor, and generally dried out fairly quickly.

But in the valley in question, the water has seeped under the lead and not been so easily dried out, hence the complete disintegration of the lower part of the valley rafter. Quite a graphic illustration that I thought worthy of a photo or two.

I noticed a similar pattern when repairing the main house roof. It was only where water had been trapped or been able to pool that the timbers were badly affected. Fortunately, in most places the draughty pantiles allowed good ventilation and drying conditions, which protected the timbers. In fact, I reckon the attic floor and upstairs ceilings were more damaged by water ingress than the actual roof timbers.

Good ventilation really is the enemy of damp and its associated problems.

 

[Lime]

The lead appears to have been nailed for most of its length too.
IME this type of valley is often used as a walkway so the lead needs to be fully supported on wood.

 

[AMc]

Very interesting pictures!

 

[Flyfisher]

IME this type of valley is often used as a walkway so the lead needs to be fully supported on wood.

The lead was originally well supported on the valley boards but they have also suffered very badly from water ingress, as can be seen in the photos.

Fairly good progress was made today and I should have the whole corner section of this roof rebuilt by tomorrow. I'll try to post some more photos over hte weekend.

 

[MatthewC]

The middle length of lead is about 2m, well over the maximum of 1.5m recommendation in my Lead Sheet Association handbook. I'm pretty sure the consequence of this has been the two splits shown in the second photo (due to many heating/cooling cycles).

I'm going straight outside to check whether my roof was done properly!

 

[Lime]

Hang on!

The maximum recommended length of lead in gutters/valleys etc is dependent on the thickness.
Code 4 max length 1500mm max overal girth 750mm
Code 5 max length 2000mm max overal girth 800mm
Code 6 max length 2250mm max overal girth 850mm
Code 7 max length 2500mm max overal girth 900mm
Code 8 max length 3000mm max overal girth 1000mm

i.e. the thicker the lead sheet the larger it can be.

 

[Keith Bowman]

Hang on!

The maximum recommended length of lead in gutters/valleys etc is dependent on the thickness.
...........
i.e. the thicker the lead sheet the larger it can be.

And heavier! I should have thought the limiting factor was caryying it up a ladder

 

[Flyfisher]

Hang on!

The maximum recommended length of lead in gutters/valleys etc is dependent on the thickness.
Code 4 max length 1500mm max overal girth 750mm
Code 5 max length 2000mm max overal girth 800mm
Code 6 max length 2250mm max overal girth 850mm
Code 7 max length 2500mm max overal girth 900mm
Code 8 max length 3000mm max overal girth 1000mm

i.e. the thicker the lead sheet the larger it can be.

Fair point, but this is an agricultural outbuilding so not really the sort of thing that anything thicker than code 5 would be used for. I'm pretty sure the lead in question is code 4 but whatever it is it has quite clearly failed and caused a great deal of damage. Lead might be expensive but trying to save a few 6-inch overlaps has certainly been a false economy in this case.

 

[Flyfisher]

Because of the rainy weather forecast for all of last week, I went to the trouble of building a cover so that I could continue the roof repairs regardless of the weather. Needless to say, this worked so well that we actually had hardly any rain at all! :evil:




But I did manage to complete the repairs of the badly decayed valley as shown below . . . .



. . . though I only had time to felt and batten one face of the roof, so still plenty of work ahead.