Blackjack on House Roof

paperclap

Hi all,

So we have been having a few roof leaks lately (as you probably all know by now, haha!), especially during heavy rain and heavy winds.

Having just spoken to my neighbour about our roof, and subsequently his roof, he too has told me his old bitumen felt has gone. It’s completely shot.

In and around the problem areas, I have tried to trace them to where I believe the water is coming in. Using some decent all-weather silicone, I have tried sealing the areas.

Over the years, he has had some roof leaks which he has traced back to the hip and ridge areas. This is no doubt due to old, broken mortar, which has created a passage way for water to creep in. To solve this, he has used Blackjack on the issues, and hasn’t had any problems after.

Has anyone ever used Blackjack on concrete roof tiles and the surrounding mortar (ridge and hip areas)? I had thought it was largely used for bitumen felt roofs on sheds and the like.

I had the (maybe crazy) idea of running Blackjack up and down all the hip and ridge tiles.

In hope that we can push back on having to have a roof replacement until a few years, or at least next year (summer).

What do you think?

Thanks one and all. Don’t know where I’d be without this forum and all you lovely lot.

Bendy_House

Will Blackjack stick to the tiles and mortar and seal it effectively? Yes, it should as it's very sticky and very waterproof stuff. So if your issue is down to very fine cracks in the ridge tiles and/or porous bedding mortar, it should do the trick.

Mind you, so would many other brush-on roof sealants such as Cromopol (and similar -pol products) which have the significant added benefit of a fibre content which helps ensure a crack-bridging coating.

As it happens, I have a tub of both in my garage. The Blackjack's intended use is on an exposed kit-car chassis where its tar-like adhesiveness should see it work effectively, and the Cromo was used earlier this year on an ageing felt roof where it proved to be very effective, filling and bridging some pretty sizeable cracks.

The Cromopol will also be a much nicer material to apply - really quite pleasant to brush out - whereas the Blackjack is really messy. So, to seal and cover cracks, I'd say the Cromopol-type products will be more suited - it is exactly what they are designed for.

Available in grey, black and white - and a 'clear', but which has no fibre content.

paperclap

Thanks Bendy_House!

Had never heard of Cromapol before.

What do the fibres do, and why doesn’t the clear variant have them?

Bendy_House

The fibres act like a material 'mat' and bonds the adhesive part together - it turns the set product into a continuous 'sheet' and not just a coating. It copes with much more movement, and it actually covers - 'skins' - even sizeable cracks and holes. It's also much stronger and tougher as a result of the fibre content.

I understand Blackjack is also good at remaining flexible, so should cope with some movement. But, like paints, if you flex it too much, it'll crack or split - it is ultimately 'just' a coating. The fibres in Cromo turns the whole into a continuous flexible sheet, bonded together - it's effectively a 'composite' material.

Are you familiar with how GRP roofs are laid? It consists of two main parts - the resin (which is strong stuff, but usually brittle) and a glass fibre strand matting. It's the matting which turns it all into a continuos 'sheet', and adds hugely to its strength.

The clear version of Cromo doesn't have fibres as it would no longer be clear! I suspect it'll still do as good a job of sealing porosity and fine cracks as Blackjack will, tho', but won't be as overall effective as the fibred versions, at least not on obvious large cracks, holes and stuff. Check out what the clear is used for, and ask them questions if needed - explain what your intended use is for.

Bendy_House

Bottom line, I have used Cromo and I know that it works extremely well. I would be absolutely confident that it would fully seal your ridges and hips and would last years.

Very good chance that Blackjack would too - provided the gaps/cracks weren't too large - but Cromo is made for this sort of job, and is also a lot nicer to use.

Cromo can apparently even be applied to damp surfaces, tho' I would always recommend it isn't.

And Cromo will have a matt/satin finish which I think will be more in keeping, whereas Blackjack has a shiny finish as I recall - it'll look as tho' your ridges have been 'tared'...

Bendy_House

I've just checked my tin of Blackjack - it should do your job equally perfectly.

Section62

laurencewhymark said:

To solve this, he has used Blackjack on the issues, and hasn’t had any problems after.

Bear in mind "Black Jack" is just a trade name for a range of waterproofing / roofing products. It isn't a single product.

The properties and usage of the individual products varies widely, you need to ensure you've identified the correct product for your needs.

I'd also only consider using it if you are sure you will be completely redoing the roof within 12 months and will be using brand new tiles throughout.  Having had a bitumen (or similar) based waterproofing applied to them the tiles will be permanently affected and will look a mess if you were hoping to be able to reuse them.

Bendy_House

Good point - I was referring to Everbuild Blackjack, a liquid DPC.

Bendy_House

Laurence, if I were you I'd fully check out the 'clear' Cromopol and see if it is effective at sealing porous and hairline-cracked mortar. If the answer is positive, then I'd be inclined to use this in the first instance.

There remains the option of adding the fibred version - or a completely different product - afterwards in the unlikely event it didn't work.

paperclap

Thanks everyone.

Here, it states "This product is not suitable for use on roof tiles."

https://www.roofingsupplies4u.co.uk/cromapol-f-clear-roof-coating-5-litre.html

Whereas here, it states "It can be used on Flat or pitched roofs, roofing felts, fibreglass..."
https://www.amazon.co.uk/Cromapol-Acrylic-Waterproofing-Sealant-Reinforced/dp/B01N3QO5AB/ref=asc_df_B01N3QO5AB/?tag=googshopuk-21&linkCode=df0&hvadid=309950300084&hvpos=&hvnetw=g&hvrand=6824007821599138678&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9045807&hvtargid=pla-696499559013&psc=1

Bendy_House

It also, annoyingly, doesn't mention masonry - the two substances you do want to use it on!

Are you planning to DIY this? Do you have safe access to the ridge? Have you been able to have a good look at it to see what sorts of issues there are - cracks or actual missing chunks of pointing?

There must be a specific reason why they say 'not suitable for roof tiles', and I doubt it's that it won't adhere or seal a crack on there - it'll be something else, like they know it's not suitable for covering what will be moving panels, or there don't even want you to try and seal around the tiles which would stop natural ventilation. It's one of these comments that 'doesn't make sense' on its own!

I cannot think of anything this stuff won't stick to.

Can you take a photo of your ridge? If so, I think it would be worth contacting them to clarify whether it would do the job you need, or just to ask what they mean by 'not on roof tiles'!