Lead flashing or non lead flashing?

[Ollie78]

I am about to build a little lean-to roof over my patio doors, mainly so we can open them even if its raining. I will use a simple timber frame and single sheet of twin wall polycarbonate 2.1m wide and 2m long, this is nice because I won`t need any joins in it and I have some reclaimed joists already.

My issue is to do with the flashing which needs to be along the top and down one edge. I was just going to use code 4 lead and chase it in, then I thought maybe there is an alternative.
However, looking at all the alternatives they all seem to be some kind of sticky type of thing, even the zinc one I found is self adhesive.

To my mind the point of the flashing is to float above the tile/plastic roof keeping the water off but allowing expansion and contraction, to use a sticky (even if flexible ) flashing seems like a worse idea to me.
Particularly as my house has pebbledash (who invented this and have they been suitably punished for it !!? ) so there is no way I would get a good seal with what amounts to posh sticky tape.
Looked at the various things supplied by the plastics company and they will all need a secondary flashing, lead or otherwise or vast quantities of sealant along the top and seem to just be a pointless step.

Any further insights into this would be welcome, but at this point it looks like I have no alternative to lead.


Ollie

 

[steve355]

What’s wrong with lead? Easy to work, stays in place, not too expensive, lasts a hundred years or more.

I have to admit I’ve only done it once (flashed a chimney stack I built) but I liked it.

 

[Bingy man]

I can’t imagine even trying to seal a pebbledash wall with what effectively is flash band by any other name . Lead will last forever especially if it’s sealed and painted. Not used a lot where I live because of the dreaded metal thieves.

 

[Cobbs]

Having worked in the roofing (slate) game for the best part of thirty years, I think it's safe to say that lead is the best option - it may be a bit pricey and a bit harder to fit, but you get what you pay for. Chase it into the wall by about an inch, don't forget to use a good sealant designed for lead and don't use any lengths longer than about 6 foot horizontal, 3 foot foot vertical, with a good 6" lap on any joins. Plenty of how-to stuff on the internet, so read up first.

 

[carpenteire2009]

Lead is the way to go and if done even half right it will outlast what your proposing to build. I did a lead flashing job on a much bigger lean to roof a few years ago, using basic hand tools, a lead working guide I'd downloaded for free and some helpful youtube videos. Be sure to use patination oil on the finished leadwork.

 

[Ollie78]

Thanks for the replies, you have confirmed my suspicions. I will use the lead.

Ollie

 

[trvlr]

lead every time… sticky on stuff is a bodge

 

[okeydokey]

I was going to suggest a torch on roofing felt such as a capping felt then thought the polycarbonate sheet might not take the heat, then lead does seem best but its 2.1 m wide and 2m long so it may be tricky/heavy across the length/width to actually fit. Perhaps you dummy fit the roof then mark where you need to chase the wall - remove sheet chase the wall fit lead with sealant then slide the polycarbonate under the lead into position. Good luck
edit
perhaps do use a good quality self adhesive flash band (Bosch do one) as long as the pebbledash is dust free I am sure it will be waterproof enough - how waterproof does it really need to be?
https://www.branchbros.co.uk/bostik-flashband-flashing-tape-300mm-x-10m--1

 

[Yorkieguy]

The pebbledash is a complication, and if you can't chip it smooth enough to allow Flashband to fit, then you're going to have to chase out a groove in the wall for lead, (maybe with a masonry disc in an angle grinder?), but of course, you'd still need the pebbles chipped away to be able to dress the lead upstand against the wall.

I wouldn't dismiss Flashband out of hand.

I have a timber workshop I built in 2001, with a pitched roof, which I covered in slate shingles, with Flashband along the ridge. I still looks as good as new, unaffected by extremes of weather over the years. In 2011, I built a lean-to woodstore for my son's house against a stone wall, the roof being artificial slate. I dressed the stone wall smooth and fitted Flashband. It adhered really well and is still fine.

Likewise, in 2013 I converted my pent-roof garden shed to a pitched roof, with felt shingles and Flashband along the ridge. That too is as good as when it was fitted. (It was done in winter, so I built the roof trusses in my garage and did a trial fit. I used the T&G wood reclaimed from the pent roof, plus some new boards).

A few pics attached, though they're not close-ups of the Flashband. For the pitched roofs, lead wouldn't have been an option, lead wouldn't have been an option. For the woodstore, lead would have entailed chasing a groove in the stone, and would have cost more than was warranted.

Hope that's of interest.

Good luck with the project.

David.

 

[Lard]

I was interested to read the positive comments on Flashband as I've used it several times, in lieu of lead, and not had any issues. I've heard many negative things but they all seem to be hearsay.

Anyway back back to flashings, just wanted to note that I've made a few out of left-over coloured profile roof sheet edgings (the 90 degree barge sections), using the rolled edge as the viewed edge......disc-cut into masonry, wedged and sealed. Very very sharp edges mind you that have to be treated carefully.

 

[trvlr]

Flash band requires a pretty flat surfae and clean/firm (as dust free as possible). Lead requires one chase out the wall to a depth sufficient/advised into which to insert the lead. That is a dusty job and one best uses a grinder with appropriate disk or is ready to spend an age with a masonry chisel. I can see where flash band has it uses - typically on ridges of apex roofs, and maybe even to seal an overlap of two surfaces or even a butt join; but it wil require proper sealant to ensue that to upper edge of the tlayer (the one overlapping onto a lower layer) remains water tight... I have used it in the past - where on might use lead and found the lead was best in the end.

If doing any grinding etc. of masonry (bricks/mortar...) wear safely goggles and a decent dust mask. You'll be surprised just how much stuff you you'll create and be risk in inhaling or getting into your eyes; and even consider some decent work gloves too. Also mark out a line to follow - for which ever system you choose.

 

[Bingy man]

Like with most situations it’s the appropriate application that matters most , I’m no roofer but ive used lead when it’s a straightforward joint to a flat roof or similar, on other jobs it could be that the customer is asking for a alternative to the expensive lead which tbh is one of the 1st things these lowlife metal thieves will target especially when it’s easy to remove at low level. On the occasions that I’ve used flashband I’ve removed all loose dust/ paint and debris. I’ve then painted area with bitumen as a primer ( warmed wall with a roofers blow lamp in winter/wet weather) allow it to cure then apply flashband and use a rubber roller to flatten/ smooth it out . Like most have already said lead is the bees knees and will last a lifetime if the thieves don’t get it . Flashband fitted correctly will also last many years but will never outlast lead -it’s horses for courses..

 

[TomGW]

I'd go with lead too. I would also try to grind the pebbledash below the cut and possibly fix a bit of bullnose timber to dress the lead over. A narrow strip of 6mm marine ply would be ideal, screwed and stuck to the wall and then the lead dressed over it.

 

[Ollie78]

Thanks for the further input.

I think I may well end up chasing out a wide strip from the pebbledash on the flat end above the doors, enough to sit the timber against the brick/block or whatever is under it. To be honest there is only about 600mm above the door anyway, it might just fall off !
Build the frame in position, test fit and mark the roof sheet, remove it and then chase the slot out for the lead, fit the lead in the slot, pre bent for the roof perhaps fitting a stop bead (forget the proper name) under the pebbledash which might need a bit of cement filling after.
Then fit the plasic roof and dress the lead into position, fit guttering and maybe a bit of plastic fascia.

I certainly won`t use the bitumin type flashband because I remember a friend of mine had a small lean to over a walkway, it was leaking so he applied flashband with primer and everything. During the next summer it moved so much it was splitting and it made an awful mess that was impossible to get rid of.
Some of the other alternatives seem better like the Klober stuff or leadax but not a great deal cheaper than lead anyway.


Ollie

 

[powertools]

I don't want to go against the advice you have been given but I cant see the point in using a flashing that will last for 100 years on a polycarbonate roof that may well only last 10.

 

[dannyr]

Slightly beside the point, but what historic accident stopped the use of zinc as a major roofing material in UK? - acres of it in the smallest Euro town, esp France - used as flashing, edging and for many complete roofs. - lighter, cheaper and not v worth nicking - lasts nearly as well as lead. Somewhat stiffer (good and bad) but used in thinner sheets,

I wanted some to cover a dormer top - suggestions from suppliers - go over to France to get it.

 

[Ollie78]

Slightly beside the point, but what historic accident stopped the use of zinc as a major roofing material in UK? - acres of it in the smallest Euro town, esp France - used as flashing, edging and for many complete roofs. - lighter, cheaper and not v worth nicking - lasts nearly as well as lead. Somewhat stiffer (good and bad) but used in thinner sheets,

I wanted some to cover a dormer top - suggestions from suppliers - go over to France to get it.

This is so true, I looked for zinc as I thought it would be a simple solution just get a strip long enough and bend it to shape, use like lead really.
The only one I could find here has sticky stuff on. Metal roofing is much more popular in Brittany where we often visit and also Germany, its just normal in Europe while here it is seen as a posh premium product for grand designs type projects. I suspect a conspiracy in building control and backhanders from the evil roof tile manufacturers !!
Its the same with roller shutters on windows, everyone has them in France but they barely exist here at all.

@powertools
In a way you are right, which is partly why I was looking at alternatives but in the end to get a satisfactory result it looks like lead is the best job for my pebbledash situation. Eventually we want to do a proper extension at which point at least I can weigh it in for beer tokens.

Ollie

 

[MikeJhn]

If you have a plunge saw and rail, get a masonry disc that fits the saw and use that to cut the slot for the lead flashing. The lead flashing generally needs wedging in place with small folded over pieces of lead before pointing.

 

[profchris]

This is so true, I looked for zinc as I thought it would be a simple solution just get a strip long enough and bend it to shape, use like lead really.
The only one I could find here has sticky stuff on. Metal roofing is much more popular in Brittany where we often visit and also Germany, its just normal in Europe while here it is seen as a posh premium product for grand designs type projects. I suspect a conspiracy in building control and backhanders from the evil roof tile manufacturers !!
Its the same with roller shutters on windows, everyone has them in France but they barely exist here at all.

@powertools
In a way you are right, which is partly why I was looking at alternatives but in the end to get a satisfactory result it looks like lead is the best job for my pebbledash situation. Eventually we want to do a proper extension at which point at least I can weigh it in for beer tokens.

Ollie

A search online for zinc sheet found quite a few suppliers - eg Natural Zinc Sheet - High Quality Sheet Metal (not recommended, just the first proper result).

 

[Krome10]

If you have a plunge saw and rail, get a masonry disc that fits the saw and use that to cut the slot for the lead flashing. The lead flashing generally needs wedging in place with small folded over pieces of lead before pointing.

Or Hall Clips if you're feeling flash with the cash and want to save a bit of time...