Repairing crumbly mortar on roof

[aveatry]

I have a two year old 3x3m singlestory extension with a pitched roof but also with a gable and 2 valleys, the mortar used seems chalky seems to soak up water, some of it has come away 5-10mm thick other parts are quite thick, and some is sound.I don't want to go digging out sound stuff in order to get a good depth, I thought I could use epoxyset 105 http://www.everbuild.co.uk/index.php?route=product/product&product_id=155 on the thinner parts, and normal mortar with water proofer additive (already got) on the thicker parts as I don't think skimming the thin bits with normal mortar will last. And then painting with a cement water proffer for the future. Now if i used the mortar repair on the apex it will be seen so can I use as the water proffer silka waterproof coating http://www.screwfix.com/p/sika-waterproof-coating-5kg/83502.
Or just use plastering sand and cement with my waterproofer for everything and then put the silka on topSo many products I do not know which to use - has anyone had any experience with any of these please and can the everbuild 105 be mixed up in smaller amounts.
View media item 63724 View media item 63733 View media item 63732 View media item 63734 View media item 63735
Im sorry I was having a problem so had to re upload pics and are now in a different order

 

[dann09]

1. This post should be transferred to the roofing forum - ask mods.

2. If we were doing the remedial job, we would lift all the verge and valley tiles and re-do the job properly.

3. Others might have more advice ref your epoxyset proposal.

4. Pic 1. shows crumbling S&C that was applied as a too sloppy mix, with perhaps too little cement.

5. Pic 2. shows the GRP valley discharge, but another is pic req'd to show a more broader view. Pointing as in pic 1.

6. Pic 3. shows original application of pointing, (with slips) has been pointed over, but the over pointing has not bonded.

7. Pic 4. appears to show a lopsided valley and the right hand valley edge becoming exposed. Do you have any leaks?

 

[aveatry]

Thanks for your reply
I put in the building section and not roof as the question I thought was just about reparing mortar and the buil section would do
I have no leaks as yet and I want to sor this before i do
I am not keen on the take off and redo idea as the ceiling below is vaulted as the roof and perfect plastering and I do not want a lot of heavy moving about up there as I know my perfect ceiling is gonna crack
The mortar when it was done was not in any way wet and was very stiff
View media item 63730 wider view pic
So most of it is sound incl the ridge it just loos a mess on the feature window. Its like the water gets in to the mortar and then freezes and crumbles it

Can someone recomend a paint-on warerproofer

 

[dann09]

A stiff S&C mix, in correct proportions, is unlikely to shrink and crack as your mix has done.

Perhaps others can help you further.

 

[aveatry]

It was very stiff - so the mix was too weak then.
I was wondering about useing plastering sand as - isnt that much finer and I could get it into the parts that are cracked better than a grainy sand. Once that is dry this looks the way to go http://www.screwfix.com/p/no-nonsense-water-repellent-seal-clear-5ltr/57474# as it is solvent based and what I read is better than the well known make that is now water based
I think that I am basicley buttering up and in other parts where I can pull out chuncks I will be replacing, Im just not sure if the verge and gable "skimms" will hold-- is there a primer I can use