New Roof - Punctured Membrane - Update

[jonez]

Hi,

New here so be kind if this is a stupid question. I'm looking for a reality check on my opinion about a slate roof I just had refitted.

They 'finished' yesterday and I had a good look at the work this morning. Problem is there area few defects, one of which seems pretty bad.

They fitted a Tyvek membrane which is water impermeable but allows water vapour out. Unfortunately they fixed the slates with nails which are too long for the laths so the membrane is punctured in a lot of places. Where it isn't actually punctured the nails are pushing into it making a cold bridge so big drops of condensation are forming at the points.

I can't see how this can be fixed without stripping the roof and fitting it properly. Although Tyvek can be repaired with tape, it's damaged in so many places it would look like a patchwork quilt when they finished.

It seems to me just plain substandard work to have nails stuck right through the laths. Is that right or am I being too picky?

Cheers

Tony

 

[advancemaintenance1]

its definately shoddy workmanship dont even think of redoin it you could push membrane onto nails then grind them off and like you say have a patchwork quilt did you pay him in full

 

[jonez]

Thanks for the reply am1. I paid about 80% in advance of the job finishing as a goodwill gesture. The company is a large contractor and not a one man band so I felt reasonably confident to do that, maybe a mistake.

It'll get sorted one way or another, if it gets out of hand I have insurance to do the legals so I'd just hand it to them.

Reason for the question is the scaffold is still up so I want to know if I should go in fairy robustly, reject the work and give them the option of leaving the scaffold in place to reduce their costs for the rework, or whether I'm over reacting to the size of the problem.

 

[advancemaintenance1]

i would definately tell them that it isnt right and you wont be settling the remaining 20% until its sorted. at the end of the day the job aint done right and no matter how much you owe you are within your rights not to pay them. just dont let them blag you that its standard practice ie extra breathing or for aesthetics iv heard some bull in my time believe me. hold your guns and maybe they will sort it or the 20% you have, will pay for it doin to a satisfactory level for you. your the customer you have the money believe me you are always right

 

[datarebal]

It can not be put right without stripping and fitting of new underlay.
No amount of faffing around grinding, stiking tape on etc wil make it right.
Problem is fixings too long and or batten (lathes) too thin..

out of curiousity what size batten and nails were used and have ou got an external pic?

 

[Chukka63]

Bodge Job.

 

[jonez]

Thanks for the replies, confirms what I thought.

Datarebal - can't access any laths but the job spec. has 38 x 25mm.

Here is a pic of part of the roof and one of the many nails poking through the membrane. Click the thumbnail for a larger view.

Untitled

• jonez
• 20 Dec 2009
• 1

Untitled

• jonez
• 20 Dec 2009
• 1

Have written to the contractor rejecting the work and we'll have a site visit on Tuesday. Company has a good reputation so I'm hopeful they'll do a proper job of fixing it.

 

[datarebal]

I would have expected to see more nails showing through.. I might guess that the odd few longer nails were mixed in and not rejected during slating. Maybe there was an improver onsite ?
batten we would use 25x50.. but at least you have the thickness..
the roof looks fine and shame to rip it off..

 

[jonez]

Yes, happy enough with the way the roof looks from outside. Found one slate on the valley which has been cracked by some rough cutting but other than that it seems well set.

About 30 nails are showing through and by feeling the laths through the membrane I'd say about a third of the nails are too long. A lot have stretched the membrane without puncturing it but as the wind whips it about they are working their way through too.

Shame to rip these slates off, they were only nailed on twice - once 170 years ago and again last week. Ripping and nailing them again will just trash some and leave the rest a bit more damaged.

Good point about the improver, there was one experienced roofer and his 'lad'. That might explain it.

 

[jonez]

Thanks to those who posted replies to my message, here's an update.

The director of the roofing firm quickly agreed that the job was substandard and that it would be done again. For the last two weeks they've been stripping it all off and replacing it.

When the slates were removed I could see why some nails had punctured the membrane, some had gone through a slate and instead of pulling them out they'd just been hammered flat into the lath. All the others were protruding through the laths to some degree, all the nails were 35mm long which seems to be too much for the 25mm laths + the slate thickness. From what I've read it should be 15mm + 2x the thickness of the slate.

Although the new membrane is in much better shape there are still a few snags. There are some rips in it which haven't been patched and a few long nails that have missed rafters.

The issue that's bugging me is that I found a split slate alongside a valley, half was missing so they'd propped a slate fragment behind it to make it look complete. When I pointed it out they said they'd fix it but all they've done is stick another slate in place with a blob of silicone compound. When I checked it a few hours later it had already started to slip down.

This seems to me a simple example of dangerous work. An unsecured slate could hit someone on the ground, or in the location could hit a train. If they're prepared to do that what's the rest of it like?

Another problem is that they insisted on using chloride admix in the ridge tile mortar in spite of me asking them not to. Chloride attacks ferrous metal and the nails in the top row of slates will be affected.

The way the membrane has been placed doen't seem to meet the spec. described by Dupont. As I understand it the membrane can be placed taut and counterbattened or can be draped with a 10mm sag between rafters and with no counterbattens. It's been fitted taut with no counterbattens so the drainage and ventilation is blocked outside the membrane. One side effect is that there are many nails which have been dropped jammed between laths and membrane.

Tricky situation, I don't have confidence in them now so I don't want them back to do any more corrective work. I think I need an expert opinion, maybe from the local building inspector and then take a view on what needs to be done.