'Lead alternative' flashing

[JohnW2]

It was just stuck in place, then I think a small roller was run over it, to improve the stick.

Fair enough. As you will presumably realise, I asked because I was wondering whether it had been 'mortared in' to a chase, given that the Flashband documentation indicates that it can become brittle if in contact with "cementitious mixes"!

Kind Regards, John

 

[JohnW2]

I also remembered using some on nailed down felt - where there were joints, and possible movement, the Flashband split due to the movement.

Ok - maybe that's the sort of joints they were thinking/talking about - so not relevant if, for example, stuck to brickwork.

Kind Regards, John

 

[Harry Bloomfield]

Fair enough. As you will presumably realise, I asked because I was wondering whether it had been 'mortared in' to a chase, given that the Flashband documentation indicates that it can become brittle if in contact with "cementitious mixes"!

I didn't see that on the original instructions, but as said it was primarily done as a secondary seal, over the top of the lead and chimney pointing, as a quick fix.

 

[JohnW2]

I didn't see that on the original instructions, but as said it was primarily done as a secondary seal, over the top of the lead and chimney pointing, as a quick fix.

Fair enough. I suspect that the instructions I saw are quite probably being somewhat over-cautious - to have to avoid contact with "cementitious mixes", acidic or alkaline materials, oils and solvents, silicone sealants, flexible PVC and vinyl could be pretty restrictive!

Kind Regards, John

 

[robinbanks]

It's a while since I last handled, or had to hand, any Flashband, but isn't the aluminium layer below the 'rest of it' which may need to be protected from UV?

Not on the stuff I've used. I'll find some in the garage if you like and slice it up. Long story short; top side lead coloured aluminium, bottom side black sticky bituminous stuff

I'm not sure what sort of 'not taking kindly' you are thinking of.

Mortar being alkaline and aluminium (as opposed to Alu oxide) in particular reacting with it. Sealant might be better.

 

[JohnW2]

Not on the stuff I've used. I'll find some in the garage if you like and slice it up. Long story short; top side lead coloured aluminium, bottom side black sticky bituminous stuff

Thanks. As I said, it's some time since I handled any of it, so my recollections were probably faulty.

Mortar being alkaline and aluminium (as opposed to Alu oxide) in particular reacting with it.

As I have subsequently discovered, and quoted above, that seems consistent with what the Flashband data sheet says.

Sealant might be better.

It would seem so, provided one uses a solvent which contains no "oils, solvents or silicone"

However, as I wrote in my recent post, I suspect that (despite the chemistry) all these 'warnings' (including the one relevant to mortar) may well be erring on the side of caution, at least in terms of the short- and medium term.

Kind Regards, John

 

[robinbanks]

It also says:

Is this referring to 'joints' between lengths of Flashband?

Kind Regards, John

It refers to joints or abutments in the substrate, I guess because FB is more often used as a temporary repair - don't stick your abutting roofing sheets together with FB stuck immediately to either side of the joint line; place something that prevents it bonding to the substrate (like a rip of then plastic backing that stops it adhering to itself when in the roll) across the gap so it has a flexible forgiving section - "what gives won't go"

 

[robinbanks]

.

It would seem so, provided one uses a solvent which contains no "oils, solvents or silicone"

I'd imagine the oils//solvents would be particularly detrimental to the bituminous side

 

[JohnW2]

It refers to joints or abutments in the substrate, I guess because FB is more often used as a temporary repair - don't stick your abutting roofing sheets together with FB stuck immediately to either side of the joint line; place something that prevents it bonding to the substrate (like a rip of then plastic backing that stops it adhering to itself when in the roll) across the gap so it has a flexible forgiving section - "what gives won't go"

Yes, that all makes sense, if it is being stuck to something like roofing sheets.

Kind Regards, John

 

[JohnW2]

I'd imagine the oils//solvents would be particularly detrimental to the bituminous side

I'm sure that's the case. I can't think of any oil or solvent that would harm aluminium, but imagine that many could be a problem to the bituminous side.

However, if there were any significant amount of oils/solvents around (I would think pretty unusual in the environment, but maybe present in some sealants etc.), I imagine it might be difficult to be sure it wasn't going to get to both sides. Indeed, if it had access to sides/end of the tape, I imagine that such a substance might creep progressively under the tape, as it dissolved/damaged/whatever the bituminous coating. However, there are no such substances in the environment which interests me

Kind Regards, John

 

[Harry Bloomfield]

Not on the stuff I've used. I'll find some in the garage if you like and slice it up. Long story short; top side lead coloured aluminium, bottom side black sticky bituminous stuff

My memory agrees with that - aluminium, bitumen, then adhesive. The aluminium layer seemed to be quite stretchy, but maybe a bit thicker than cooking foil.

 

[JohnW2]

I think I have come to a decision, which is not only somewhat of a 'compromise' but also should serve to some extent as an experiment and learning experience.

As previously said, I'm not inclined to use lead, mainly because I'm not 'public spirited' enough to see the sense in paying appreciably more in order to achieve something which will live much longer than I will, and hence will only benefit someone other than me !

That leaves the other two options. On the basis of what I have seen so far, I don't think that by any means all of the flashing needs repair/replacement - the issues relate primarily to one of the sides of the roof, with a few other possible issues elsewhere.

My current thought is therefore to use Ubiflex for as much as I can do with one roll, and then use Flashband for what is left (probably mainly things which may not even 'need to be done'). That will teach me the relative differences of using the two products and, if I am able to observe for long enough, the relative medium-term performance/survival of the two products. This plan has been made even more attractive by the fact that I have discovered that a colleague has a roll of Ubiflex of an appropriate size (in 'damaged packaging') which he is prepared to sell to me for appreciably less than the retail price!

Given what has been discussed, I may well not do the Flashband+mortar experiment.

Somewhat 'messy' an approach, I agree, but I wonder if anyone has any thoughts about it?

Kind Regards, John

 

[JohnW2]

My memory agrees with that - aluminium, bitumen, then adhesive. The aluminium layer seemed to be quite stretchy, but maybe a bit thicker than cooking foil.

Thanks. I'm going to get some soon, so will be able to see for myself. If the aluminium layer is anything like cooking foil (but a bit thicker),I wouldn't expect it to be very 'stretchy' - far more likely to tear than scratch if one tried to stretch it? Anyway, as said, I'll soon see!

Kind Regards, John

 

[robinbanks]

Stretchy might have meant "deformable". I've not seen FB stretch to the extent that eg lead does when it's being dressed over features such as roof window edges but I've seen it be used to wrap over old lead and it followed the profile of the substrate fairly well, but it did end up somewhat creased

 

[JohnW2]

Stretchy might have meant "deformable". I've not seen FB stretch to the extent that eg lead does when it's being dressed over features such as roof window edges but I've seen it be used to wrap over old lead and it followed the profile of the substrate fairly well, but it did end up somewhat creased

When lead 'deforms' when being dressed to conform to 3D profiles, I presume that happens by it stretching in some places (and quite possibly doing 'the opposite of stretching' in other places).

Sheet aluminium can certainly be deformed, which implies some stretching - after all, with sufficient force, a flat sheet can be transformed into the shape of a saucepan/whatever. However, when it becomes anything remotely as thin as cooking foil, I feel sure that it would tear before it stretched (or truly 'deformed') appreciably.

FB can certainly be made to conform to 3D profiles, but I would suspect/suggest that that probably isn't really achieved by 'true deformation' of the aluminium but, as you imply, is probably largely achieved by 'creasing'.

Kind regards, john