Coping stone fixing on single ply parapet

[health mechanic]

How do people fix coping stones onto a single ply (vanguard) covered parapet warm roof. The upstand and top of parapet had plywood before the single ply was lapped completely over to the edge of of the parapet. 

 

Would you SBR the the membrane, allow it to dry few hrs and then apply a cement sand mix then while wet paint bottom of coping with sbr/cement mix and apply?, but at 35kg per stone would this work or would you allow the sand cement mix to dry and then sbr/cement bottom of stone and then fix.  Also have a 45 degree area as per photo is this method okay in that area too. Would the cement mix close the membrane over the ply to protect and cappillary leakage into there

 

 

[nod]

I did this and just laid the copings on mortar The weight holds them in place 

[Brickie]

I’d be tempted to drill dowels into them all just for peace of mind. 

[Dave Jones]

more importantly get rid of that standing water, the outlet is too high.

 

Lead coping would look much better than stones and be maintenance free long after we all gone.

[health mechanic]

Don't get me started on the pool of water....whT happens when u get your builder to do random furling stripes...and a private roof company to do the membrane....cannot do anything about it now unless you know how

[Dave Jones]

that standing pool needs fixing. It's an NHBC inspection fail for starters.

 

It will caused your roof to prematurely fail, crap will build up in  it and clog that outlet (which is too small).

 

Get them back, insist on a minimum 100mm outlet so it self cleans, the bottom of which is below the height of the deck by at least 25mm so when they add the waterproof layer its still below the level to negate pooling.

 

This would be a show stopper for me, builder don't get paid etc until its fixed.

[Big Jimbo]

The roof looks great, but i would agree that the water outlet looks way to small. It would concern me that the coping stones on the slope could kill somebody if they ever came off. I have always liked to continue any rubber roof over the top of the wall, like yours. B.C. were not happy with me simply fitting heavy coping stones with just morter to the rubber roof. They wanted me to cut the rubber back. In the end i fitted powder coated ali.

[Dave Jones]

sorry for more bad news the parapet wall as detailed also fails building control. It needs a cavity closer to close off the cavity and a tray (you may have this cant see from photo).

 

These are weak points of failure when they are done really well let alone when they are wrong from the start.

 

https://www.nhbc.co.uk/binaries/content/assets/nhbc/tech-zone/nhbc-standards/tech-guidance-and-support/parapets-and-copings---revised-05-20.pdf

 

[health mechanic]

Hi dave

 

Yes has cavity tray (if i recall). The plywood and single ply acts as a cavity closer. Building regs were happy with it.  The outlet is 100mm..but agree too high. The roofing company are saying its water proof and suitable for swimming pools and do not want to change the outlet, the dip near outlet I suggested they build up to allow it to be higher than outlet, but they were not keen. 

[steveoelliott]

I have the same issue with a flat roof of mine...

General consensus was whilst it's infuriating, it is not an issue insofar as leaking / integrity. I was advised by many on here and independently that playing with this after is unnecessary and I am best to leave alone. I struggle with this knowing that under the slabs laid on top is ~40 liters of water.

[health mechanic]

@Dave Jones is it definately a building control fail having a collection of water....the most annoying thing is that pool of water outside the bedroom is causing mosquitoes to gather.

 

@steveoelliott have you had any issues since install

[Dave Jones]

yep its a fail, no ponding is allowed.

 

https://nhbc-standards.co.uk/7-roofs/7-1-flat-roofs-and-balconies/

 

Why would you put up with it anyway, its a crap job. Get them out.

[steveoelliott]

On 03/09/2023 at 23:08, health mechanic said:

@Dave Jones is it definately a building control fail having a collection of water....the most annoying thing is that pool of water outside the bedroom is causing mosquitoes to gather.

 

@steveoelliott have you had any issues since install

I have had no issues but it does drive me nuts. @Nickfromwales did give me some good advice which was to just leave it alone as it wasn't going to leak and messing with it might cause further issues.

[Nickfromwales]

It’s a complete rip-out and start over, all the way to coping’s & flashings etc. 

Real world truth, won’t matter at all and won’t affect longevity (it’s a product designed for continuous immersion and to be able to cope with the expected temperature swings), so just an annoyance tbh. 
I’ve actually never seen one done, particularly parapets, where there is zero pooling eg the immaculate installation. The vernacular seems to always be to create an unwanted hump where the final membrane meets and rises over the skirt of the up-stands, further exacerbated by the outlet adding a primary, second elevation in the picture. Ergo a 6-8mm jump or more is “the norm”. 
I’ve always found this to be a bug-bear of mine, but this has been on jobs where I’ve not project managed the whole build, but on my current project where I am the PM, this will 1000% not be accepted on new works. 
Self-builders don’t know all the places where things go tits up, and unfortunately find out after the horse (and their budget for that element) have bolted. I however, as a PM, will be directly responsible for these things having been identified, included in tenders to prospective roofing contractors, a method statement surrendered, and the consequences of it not being delivered would be known to said contractor before they’ve even turned up on site.

You cannot just get experience, it’s taken me 3 decades to now be managing exclusive, one-off private builds, and even now I still rely massively on a fantastic team under me (with overarching knowledge and expertise in their respective fields) to be confident to put myself forward for these larger projects. 
In actuality, the roofing company should have said to you that they could go the extra mile, explain the cost (labour mostly) uplift to get it “spot on”, and allow you to make an informed decision. Unfortunately they just fear losing the job to the next guy who will just shut their mouth, do what they did yesterday, and the day before, and move on to the next unsuspecting client (to churn out the same crap over & over again, unchallenged). 
You would be entitled to ask for this to be rectified, it’s up to you. Has your warranty company signed off on this?

I'm on one in Leicester, where the quintessential “Cowboy Builder” was employed, and there is pooling on the balcony. As there will be synthetic decking on chairs atop the membrane the warranty company have said it’s ok. Maybe they should have kicked off? Honest answer is, it’ll make no big difference and once it’s ‘invisible’ life will simply go on.

As I am now PM on that project (after having said scrotum-faced builder ejected) I will make the last 2 planks of the decking removable for an annual scrub out / routine maintenance etc, as there are trees and a lot of ‘nature litter’ that gets on there too, however natural draining of the rainwater would not be enough to make those outlets maintenance free.

 

Is it worth thousands in upheaval? Nope.

 

Did the warranty company accept it as a deviation? 
Yup.
 

That’s been received from them in black & white as I asked for it after they inspected. Note, they never asked to see a hose on it / other demonstration of functionality either…..🤷‍♂️