Cement anti crack additives for roofing?

[JOEPRO]

As I continue to repair my roof after recent storm damage I need to repoint the 2x valleys on my house. Short of re tiling the whole roof, there are no "dry verge" solutions suitable.

So I need to re do the pointing to the exposed edges of tiles with black cement:



I have used the liquid anti frost additives before. But still after a couple of years the pointing tends to crack and fall out.

Are there any modern anti crack additives might help to prolong the life of the pointing? Maybe fibreglass strands into the black mortar mix? Thinking the fibre may help it stay put better.

 

[Nomad]

I painted a cracked cement roof with a U-pol ( liquid waterproofing with fibreglass mat strands), it's quite thick so you can shape it - or use cement to give the basic shape then put this on top to waterproof it?
The tin I got was pale grey but I see they do other colours..

Brave Search

Search the Web. Privately. Truly useful results, AI-powered answers, & more. All from an independent index. No profiling, no bias, no Big Tech.

search.brave.com

Something to think about?

 

[Morrisman]

What about the glass fibres additive for concrete, to strengthen it? Would that would in this situation, or is there just not enough depth to the concrete?

 

[gaz1]

my advice here is dont point it up with cement

thats a lead valley and needs to drain water out the lead should be well enough under the slates



cementing at the edge is the wrong place

cement always shrinks and cracks but lime cement dosnt

 

[JOEPRO]

my advice here is dont point it up with cement

thats a lead valley and needs to drain water out the lead should be well enough under the slates

View attachment 484220

cementing at the edge is the wrong place

cement always shrinks and cracks but lime cement dosnt

I was thinking that too. That the cement may prevent water getting into the lead tray. The lead goes go under the tiles. It was originally all cement pointed. Then fell out and I re pointed it about 15 years ago. And all fell out again. Seems like maybe a waste of time doing that again.

If I can get another 15 years or so out of this roof I'll re tile the whole lot and fit a dry valley system. New breathable underlay and battens too.

 

[gaz1]

its a galvenised tin valley nowadays instead of lead

 

[brightspark]

shot a bit of sbr bonding agent in the mix..makes it bond better and waterproofs it

 

[roofman]

As I continue to repair my roof after recent storm damage I need to repoint the 2x valleys on my house. Short of re tiling the whole roof, there are no "dry verge" solutions suitable.

So I need to re do the pointing to the exposed edges of tiles with black cement:

View attachment 484201

I have used the liquid anti frost additives before. But still after a couple of years the pointing tends to crack and fall out.

Are there any modern anti crack additives might help to prolong the life of the pointing? Maybe fibreglass strands into the black mortar mix? Thinking the fibre may help it stay put better.

Keep the valleys dry, take out the remaining mortar and leave, you will thank me

 

[gaz1]

ive done many a roof over the years and i know roofman has done the same

but there was always something grey sort of cement mix under stone or slate roofs at the time i couldnt figure out what it was

it was light weight but strong and sometimes a git to get off stuff

but its lime mortar

 

[JOEPRO]

Keep the valleys dry, take out the remaining mortar and leave, you will thank me

Thanks for that, OK yes I will just leave em without pointing. I know it will just fall out again anyway.

There are a few loose tiles in the valleys so I'll make them good and call it a day.