Repairing cracks in lead gulley

[tonybovill]

Hi guys,

I have several cracks in a lead gulley between two roofs caused by the two buildings' movement - replaced the lead and it cracked again. Since then have tried numerous bitumen based products - the best being WeatherMate - but it always cracks again as soon as we have a heavy frost.

Any ideas !?

Regards,
Tony Bovill,

 

[justlead1]

Hi. When sheet lead is laid to weather tapered gutter between two roofs. It is most important that the timber decking design complies with "Sheet lead code of practice" If this is followed EG. Bay length and widths are the correct length for the code of lead to be used. Then the life expectancy can be 100 years or more. There are other materials which can be used for this work, but all have expansion/contraction to deal with, which must be taken in to account when designing as this is normally the cause of failure.

 

[Chukka63]

replace with fibre glass,much lighter,easier and cheaper.

 

[Nige F]

www.liquidplastics.co.uk

 

[ladylola]

Agreed with justlead.

Do you have details of the size of the gully that you are concerned with here. Has the lead been fitted in one piece or are there joints to take up the expansion. Expansion and contraction are what causes the cracking, that is to say if the lead can't expand because it is tightly fixed all round then cracks will appear. Also what code of lead are you using for the gully?

Justlead I've worked on this sort of thing for years and over time have seen the lead federation guidelines change. 25 years ago we were fitting tongue and groove decking, now it's normally rough sawn with 5mm gaps. 25 years ago, too we had some very fastidious plumbers and everything had to be perfect. I can remember a b*****king or two if rebates were not deep enough or boards not flush but nowadays I've seen some more "leniant" types who will fit the lead to anything, hit the dresser hard enough with a lump and it'll go in.

 

[tonybovill]

Agreed with justlead.

Do you have details of the size of the gully that you are concerned with here. Has the lead been fitted in one piece or are there joints to take up the expansion. Expansion and contraction are what causes the cracking, that is to say if the lead can't expand because it is tightly fixed all round then cracks will appear. Also what code of lead are you using for the gully?

Justlead I've worked on this sort of thing for years and over time have seen the lead federation guidelines change. 25 years ago we were fitting tongue and groove decking, now it's normally rough sawn with 5mm gaps. 25 years ago, too we had some very fastidious plumbers and everything had to be perfect. I can remember a b*****king or two if rebates were not deep enough or boards not flush but nowadays I've seen some more "leniant" types who will fit the lead to anything, hit the dresser hard enough with a lump and it'll go in.

Reply ...................

Many thanks - the lower gulley is 8 inches wide and 20 ft long in one piece on hardwood. The higher one is 2ft wide by 25ft, also in one piece. Have no idea what code of lead was used - it was installed 26 years ago by the previous owner and cost him £4K then - God knows what it would cost now as several rows of 120 year old rosemary tiles would have to be removed on either side.

I have two cracks in the lower section and 3 in the top which I have been repairing every year for the last 20 !! Only two solutions have lasted more than a year - roofing felt stuck with hot bitumen and two layers of WeatherMate with a top quality 'rubberised' insulating tape in between.

I Googled 'roof repair tape' and came up with Sylglass and one from Westfalia - neither mentions lead as a suitable attachment material and neither company has replied to my enquiries.

Hence my request for any other ideas - even if they only last 3 or 4 years it would be worth while !?

Regards, TonyB.

 

[ladylola]

2ft x 25ft. Well there's the reason for the cracking, it's simply too big to be done in one piece. A lenght of that size would need to be broken up into four bays, each bay being raised up from its' lower neighbour by a drip detail which would be in effect a step of 65mm minimum. The lead would need to be at the very minimum code 6, 7 or 8 would be better. The higher the number the thicker the lead, it used to be in lbs, that is 7lb would be seven pounds in weight to the square foot, and as far as I know code 7 is equal to 7lb. Falls on the lead should be about 1 in 80.
Done correctly the lead will last for a great many years but as you say would be costly. May I suggest stainless steel. Very hardwaring and cheaper and lighter than lead. Zinc sheet would also be a less costlier option.
If you wish I will attempt to put up some photos of a correctly built lead roof.

 

[tonybovill]

2ft x 25ft. Well there's the reason for the cracking, it's simply too big to be done in one piece. A lenght of that size would need to be broken up into four bays, each bay being raised up from its' lower neighbour by a drip detail which would be in effect a step of 65mm minimum. The lead would need to be at the very minimum code 6, 7 or 8 would be better. The higher the number the thicker the lead, it used to be in lbs, that is 7lb would be seven pounds in weight to the square foot, and as far as I know code 7 is equal to 7lb. Falls on the lead should be about 1 in 80.
Done correctly the lead will last for a great many years but as you say would be costly. May I suggest stainless steel. Very hardwaring and cheaper and lighter than lead. Zinc sheet would also be a less costlier option.
If you wish I will attempt to put up some photos of a correctly built lead roof.

-----------------------
Thanks again. Problem is I simply can't afford to replace the entire gulley - hence my search for some form of tape or paste to repair the cracks. Liquid Plastics have now replied with what sounds like a viable if somewhat complex solution - how say you, or anyone else reading this !?
----------------------
Tony...
There is obviously greater than average stress at a particular point or 'line' along the gulley. If you can identify this 'line', presumably where the lead is splitting, then you can adopt a 'bond-break technique using Liquid Plastics membranes and reinforcements.

I have attached a detail drawing that describes the various levels of the system. This system has been used on sites for many years and has proved successful in all but the most exaggerated situations.

Product required will be...
25mm decorators masking tape (sourced locally)
Decothane Base Coat
Heavy Duty Flexitape
Reemat 300 glass fibre matting
Decothane Top Coat

If the area is not that great, you can substitute 'base coat' with 'top coat'. Goods are available by ringing our Order section on 01772 255032/255004.

I hope this will be helpful to you.

Joe Bates
Senior Technical Executive
Liquid Plastics
T: +44 1772 255684
F: +44 1772 255691
E: jb@liquidplastics.co.uk
www.liquidplastics.co.uk

 

[ladylola]

To be honest Tony I've not come across this plastic product so can't comment on how good it is. In my working life I've generally had the "luxury" of working for clients to whom cost isn't (or at least doesn't seem to be) an issue, English Heritage and the like. Cracking leadwork is normally replaced rather than repaired but on the very few occassions where a repair was done it was a welded repair, however even this is not done nowadays as hot works are rarely allowed on historical buildings, not since york minster became hotter than normal.
The "line of stress" that is talked about. Well obviuosly where the cracks are now but look also for anywhere that there appears to be any rippling on the surface and check any bends or folds where the lead has been worked as these areas can be slightly thinner and more prone to cracking.
Best of luck with the roof.

 

[Nige F]

[ Done correctly the lead will last for a great many years but as you say would be costly. May I suggest stainless steel. Very hardwaring and cheaper and lighter than lead. Zinc sheet would also be a less costlier option.
If you wish I will attempt to put up some photos of a correctly built lead roof.

-----------------------
. Liquid Plastics have now replied with what sounds like a viable if somewhat complex solution - how say you, or anyone else reading this !?
----------------------
Tony...
There is obviously greater than average stress at a particular point or 'line' along the gulley. If you can identify this 'line', presumably where the lead is splitting, then you can adopt a 'bond-break technique using Liquid Plastics membranes and reinforcements.

I have attached a detail drawing that describes the various levels of the system. This system has been used on sites for many years and has proved successful in all but the most exaggerated situations.


If the area is not that great, you can substitute 'base coat' with 'top coat'. Goods are available by ringing our Order section on 01772 255032/255004.


] I`m recommending Liquid plastics because I`ve seen their products .. their older Decadex.. in use and working well . and their newer Decothane too, it`s like rubber when it cures Liquid Plastic is almost a misnomer . I`m going to have it done on my kitchen flat roof here @ home , in a few years. Looks like the tech. exec is helpfull too.

 

[justlead1]

Hi. As sheet lead has been used for centuries, much has been learned from is performance. The result, published code of practice, outlining method of installation to achieve longevity. However new materials do not have the same pedigree. There is another option, that of having "T Prene" expansion joint welded into the existing lead gutter. The benefit being tiles/ slate only need to be removed and refitted at the point expansion joints are fitted (approx 2m apart ) However it requires welding in position and as Ladylola posted fire risk is the down side. But using knowledgeable lead workers / welders the precautions taken can minimize risk. Good Luck