How to patch chimney flu hole in spandek roof?

[GlennC]

Hello helper’s,I am wanting to patch hole in spandek roof after removing fireplace in outside room,patch needs to be watertight but not perfect,hoping to use tape under and over or paint on membrane as hole is too close to roof joins to add a piece,what would be recommended and what product suitable,Hole is a lot smaller than outer cover,Cheers GlennC.

[EricL]

Hello @GlennC 

Thanks for sharing your question about covering the chimney hole in your roof. It is technically possible to cover the hole in your roof with flashing in combination with Selleys 290ml Grey Storm Waterproof Gutter And Roof Sealant. 

However, this type of repair must be done properly and must last for a very long time as it won't be seen that often. The only time you'll ever notice that something is wrong is when there is a leak in your ceiling from the failed patch in your roof. I propose engaging the services of a professional roof restoration specialist. They will have the knowledge and materials necessary to carry out a long-term repair on your roof. Plus, it carries with it the trade person's warranty. 

Let me call on or experienced members @Dave-1 and @Nailbag for their recommendations.

If you need further assistance, please let us know.

Eric

[Dave-1]

Good Morning @GlennC 

First a question as I am a little confused.

Do you have a photo of the top of the chimeny going through the roof?

From the underside if I look closely it seems that the outer edge fits the metal roofing. The white pieces are decorative? I would be thinking of a large metal cowl for the underside to cover those cuts.

The top I cant really comment. 😕  I do think it will be problematic sealing the top of the silver tho (waterproof wise). Will wait for a photo if possible.

Dave

[GlennC]

Cheers Eric,will take all replies thoughtfully,GlennC.

[GlennC]

Thanks @Dave-1,there was/is insulation between the white slats and the roofing sheet that was cut out for the hole for the flu pipe the top photo would only show the rubber boot holding the outer pipe for flu to the roofing sheet,as diameter of hole is size of inside chimney pipe to be smaller,reason I can’t use a piece of original sheet is the hole is too close to the joint in sheet to get a reasonable water seal therefore looking at a paint on product of recommend choice,Hoping to not confuse,roofing is in good condition with no other issues,I was thinking of temporary taping under hole,painting top,remove tape under when dry and painting/sealing remainder,not sure what product would suit and stand up to weather and UV rays,Cheers Glenn.

[Dave-1]

Afternoon @GlennC 

I have been thinking about how you would seal it from the top side.

If you can take the hat off your chimney then all the better,otherwise this sketch is what I am thinking of.

A flat piece of metal (Aluminium sheet maybe) with a hole cut out that fits the outside diameter of your chimney. The corrorgations of your roof above the hole is what Iwant to cover so no water can flow down that and pool or down that and leak underneath. 

The two halves are if you cant take the hat off the top of the chimney.

You would still need to seal it with a high temperture compound Sika 300ml Sikasil 670 Fire Silicone Sealant but the clearance I would be going for is only 3mm ish around the "plate" and your chimney.

Dave

Dave

[GlennC]

Thanks Dave,I think I may have confused you as the flu and fire place are going to be scrapped,getting too old for the log splitting,hole needs to be completely closed off no boot or pipe to consider,going to air con,I do appreciate the thought and detail,Glenn.

[MitchellMc]

Hi @GlennC,

If you don't want to replace the roof sheet, you might find that leaving the roof cowl in position and removing the pipework from beneath it and patching might be a solution. Provided the roof cowl is sealing out moisture and it is not leaking, then you could just leave it in place. Otherwise, you'd probably need to use lead flashing and seal it to the roof sheet.

Mitchell

[GlennC]

Thanks Mitchell,added lead flashing to my basket,as I’ll scrap the whole lot and have a clean roof,cheers Glenn.

[GlennC]

Thanks Mitchell,what would be the recommended sealant for lead flashing to metal roofing,weather and UV wise,Glenn.