Code of lead for a raised ridge / parapet?

[dpm_dpmartin]

Good morning,

I'm preparing to spend some money on my roof. I've had 3 companies around and all 3 have said that my roof, when done back in 2014, should really have had lead put around the top of the parapet (if I'm using the wrong word there, forgive me, I mean the big chunky bit that is sticking upwards).

I've asked about this roof before on the forum (but, back then, I was focused on the horizontally projecting parts - the "projecting eave" as ree called it?) and only now have I progressed to doing something in anger / professionally about this (I did paint the horizontal bits with Thompson's One Coat Roof Seal).

I am not against them putting a lead covering around the parapet. It seems like a sensible thing to do, even if the parapet does not have questionable integrity, in my mind, a lead 'hat' should give it many years of sound protection.

Two companies have recommended Code 4 lead. One has recommended Code 5. Basic level research (prior to this I did not even know about Codes) has brought up one website that said - "We wouldn't advise using code 4 lead when the application is exposed to more severe weather or on a historical building and if using lead for parapet where a thicker gauge is recommended."

That seems to describe this roof to a tee - it gets strong wind, driving rain and it's a parapet (I think).

As always with this forum, I would very much appreciate the view of people who do this for a living or routinely. There's an obvious cost difference between the two Codes and I can stretch to Code 5, or even higher, if necessary. I really want something up there that I don't have to be concerned about for a decade. I hope to hear your thoughts... and I'll try to answer any follow-on questions you may have.

 

[dpm_dpmartin]

Sorry, I forgot - the adhesion of the lead will be done with Lead Mate, apparently. I had envisaged some kind of physical fixing, but everyone has said that's not needed. I'd welcome any thoughts on that too.

The lead sheets recommended are 3m by 750mm.

Patination oil part of the quote. So I feel everyone is telling me the right stuff, just want to get a view on the right Code to be going for. I am guessing people might say "the thicker the better", but maybe Code 4 is nearly always used for this stuff and one Roofer is going overboard?

 

[fatplumber]

In truth, the longevity of either is not the issue. The code refers to the weight per square foot. Three is three pounds etc.. The weight specced, from the practice point of view, is its workability. Heavier lead has to be used if it requires manipulation. Code 3 is too thin to be bossed into shape. Code 4 can be moved around a bit code 7 can be bossed into complex shapes. It is also used for fla rooves.

 

[dpm_dpmartin]

Interesting, so I'm looking at it from the wrong angle - using Code 5 doesn't give me 'more' in terms of protection and longevity. The text I'd read on the Internet certainly implied Code 5 would stand up to the weather better... maybe it's heavier so has less chance of 'flying away'?

 

[^woody^]

Of course thinner lead does not weather as well as thicker lead, and it also is less able to deal with natural thermal movement - requiring more expansion joints (smaller sections) - with the associated risk of leaks from the increased number of joints.

You need code 5 as a minimum for horizontal surfaces, more likely higher grades though.

And to suggest it is fitted with Leadmate seems highy amusing. Lead will last at least 100 years, normally much much longer. How long does leadmate last? 10 years?

 

[dpm_dpmartin]

Interesting too, thanks. All the lead seems to have the same guarantee length, though... that is many, many years... so why is Code 5 better than Code 4 in that respect? The answer from fatplumber seems more plausible in its reasoning. I don't - yet - see anything saying Code 5 or greater is guaranteed from splitting, cracking or wearing away for a longer period than Code 4 is.

I admit to having no idea how long Lead Mate lasts. What is the preferred long-term method of affixing lead to a structure? Putting lots of nails into it doesn't seem - on the face of it - a very grand idea?

 

[^woody^]

I don't - yet - see anything saying Code 5 or greater is guaranteed from splitting, cracking or wearing away for a longer period than Code 4 is.

It's all covered under the laws of physics, not some guarantee like you get from Argos.

 

[dpm_dpmartin]

I guess you realise that's not a helpful comment, but I also guess that's what you were aiming for?

 

[^woody^]

I thought it very helpful. The weight of lead, "the more plausible reasoning" has got nothing to do with it. Thicker lead is bound to be heavier.

Thick material resists weather and thermal stresses more than thin material. That's physics for you. That parapet will get the most severe exposure possible, and skimping on a thin piece of lead because of cost is the worst decision. You might just as well use a £10 roll of flashband.

And bear in mind that the guys didn't use Leadmate on all the lead roofs constructed during the past 1000 years.

 

[dpm_dpmartin]

Tell me more about this flashband, it sounds good to me.

 

[palaceray]

Please do not let anyone who suggests fixing Lead capping with leadmate anywhere near your roof.

The capping should be done in code 5 or over : It should be fitted in lengths of 2m maximum. The sections should be joined together with interlocking welts, each upturned welt should be fixed down with either copper or stainless clip screwed into the brickwork.

The lead should be turned down the side of the wall by at least 75mm. Before turning the lead down a continuous lead or copper clip should be screwed to the wall , when the lead is turned down it should be welted around the clip to prevent wind uplift.

Where the lead meets the corners it will probably ne to be lead burnt.

Not a cheap job but the right way to do it

 

[dpm_dpmartin]

Please do not let anyone who suggests fixing Lead capping with leadmate anywhere near your roof.

I'm resigned to it not being a cheap job, truly, but I don't want to over-specify anything unnecessarily. The reason I'm here is for that sanity check as I, myself, was wondering whether Code 4 was suitable - despite 3 reputable Roofers (and there's nothing to assert they're not) all saying Code 4, to a man.

I had one of the guys around last night to double-check a few things and he said he'd use Siroflex Grip & Grab - there's a reluctance to use any other kind of physical fittings, it seems, because of the roofing material that's already on there - I guess putting holes in something that already has an element of integrity seems kinda odd. He assured me that the Grip & Grab wouldn't need replacing or anything in the timeframe I'm going to be worried about - his work carries a 10 year guarantee (not insurance-backed).

What you are describing above - regarding the method of fixing - is, admittedly, what I had been thinking (although I do not know the terms).

It's a minefield!

 

[dpm_dpmartin]

And bear in mind that the guys didn't use Leadmate on all the lead roofs constructed during the past 1000 years.

Honestly, I definitely get that - but times move on, don't they? And, at some point, we've got to accept that better stuff is available (that time might not be now, I'm just saying that time comes with everything).

 

[dpm_dpmartin]

The lead should be turned down the side of the wall by at least 75mm.

This is a cross-section of what my 'parapet' looks like, is this bit what you mean by "at least 75mm" and is the more I have here the better?

It seems crazy (to me) that the lead won't actually protect the outward-facing part of the parapet, but it cannot because that bit is all ornamental and the house can't look like it's sat in some kind of full metal top-hat.

 

[^woody^]

despite 3 reputable Roofers (and there's nothing to assert they're not) all saying Code 4, to a man.

And there is your problem.

You are asking roofers to quote on what is specialist leadwork, in a non standard situation. It's not roofing work.