Something maybe screws popping up under PVC membrane

[steveoelliott]

Hi Folks,

 

On a recently laid PVC membrane, I've noticed there are numerous (some worse than others) objects pushing up on the membrane from underneath... I've attached pictures of some underneath; some you can't see very well in photos though.

 

My fear is these may be screws that hold the marine ply deck down on the celotex insulation boards. If this is the case, it will be a complete nightmare to resolve I presume; either membrane up or a patch work quilt.

 

I didn't notice these previously... I have made previous posts about ponding on this roof but only noticed these today whilst sweeping up some of the silt left by the said ponding.

 

I wonder if this has been caused by the recent heatwave in the UK? The membrane was replaced back in April and was previously mechanically fixed and now is glued rather than using mechanical fixings.

 

The guy that did the roof is on holiday but I will be calling him when he returns. If it is the board screws popping, I'm not sure where responsibility lies as he didn't touch this. It never did this for 10 years previous with the old membrane; maybe the mechanical fixed roof held things in place better.

 

Thanks for reading... I'd be interested if others have experienced this / seen similar.

Edited June 3, 2021 by steveoelliott

[DragsterDriver]

It’s normal to see large fixings, those do look a bit pointy though  

[markc]

They dont look like fixing heads to me, more like pieces of grit or similar

[steveoelliott]

2 hours ago, DragsterDriver said:

It’s normal to see large fixings, those do look a bit pointy though  

Thank you... When the old roof was mechanically fixed, then yes I did see these. However, they don't look like they did.

 

1 hour ago, markc said:

They dont look like fixing heads to me, more like pieces of grit or similar

 

Thanks... Not beyond the realms of possibility... the reason I suspected screws was owing to the number I have found; some are less protruding than others. The only way to tell is to the let the roofer inspect the membrane; in the meantime I intend to keep off it / avoid walking on those spots.

[Mr Punter]

It depends what was specified.  I have seen some insulation fixings where the screw is recessed far down into the large head of the fixing so if the insulation compresses the screw does not pop through the membrane.

 

Because you have pedestals and raised paving, you should be able to avoid placing a pedestal base directly on a screw head.  You can always drill or cut out a bit of the base if a clash is otherwise unavoidable.

[steveoelliott]

5 hours ago, Mr Punter said:

It depends what was specified.  I have seen some insulation fixings where the screw is recessed far down into the large head of the fixing so if the insulation compresses the screw does not pop through the membrane.

 

Because you have pedestals and raised paving, you should be able to avoid placing a pedestal base directly on a screw head.  You can always drill or cut out a bit of the base if a clash is otherwise unavoidable.

 

Thanks Mr Punter.

 

My existing membrane had a leak and I opted to replace it... I know the previous was mechanically fixed but was told it would be easier / preferable to use adhesive this time.

 

I'll see what the roofer says when he returns from holiday and takes a look.

 

I take your point on adapting pedestals because without a doubt it will coincide with their placement but it aggrieves me to need to do this on a new roof. Moreover, there is a risk that the object may still penetrate the membrane. I think either way even if the roofer deems this to be outside of their scope, I will need to get it tended to.

[steveoelliott]

I spoke to the roofer this morning... his analysis over the phone was this must just be bits of grit left over before they laid the membrane. He was adamant that they will never come through but I was far from convinced.

 

I've asked them to come around to take a look... I certainly feel uneasy leaving them as is.

[steveoelliott]

Just to circle back... The roofer came out today and took a look.

 

He acknowledged it was not ideal and suspected grit or potentially the odd screw head has popped up. He was however adamant that they wouldn't come through once the fleece is down even under weight of slab on pedestal etc. He did offer to cut out the worst ones and patch but stated if it was his roof, he'd leave it alone.

 

I still felt a little uncomfortable so in the end I made a statement... "if this roof does leak then will you take the slabs and fleece membrane off" rather than me having to do all the donkey work. He agreed but was adamant it will be fine. He said since he was here now, it would be very easy to cut out and patch the areas if he was concerned rather than the alternative of it leaking and having to deal with that.