Help please - Coated steel standing seam vs single ply ‘standing seam’ like roof

[gaschick]

Hi,

We are in the midst of a major renovation/rebuild. We need some help with deciding on roofing materials. 
We have two extensions made out of a timber frame off site. The roof for our dining roof extension has now got a 13Degree pitch, thanks to the massive steels needed for the new sliding doors. The timber frame suppliers will be putting OSB on top.
On our original plans we were going to have a Greencoat PLX standing seam roof on this extension. There are two large rectangular roof windows running through this running inline with the fall line of the roof. We were going with two sets of two velux roof windows abutted next to one another, but we are now looking at two single fixed pane windows. 

 

Our builder has thrown a spanner in by suggesting that instead of the metal standing seam we should use a single ply roofing material with a ‘standing seam’ effect. This is approximately half the cost of the metal option. 
 

Has anyone had experience of using single ply with a Standing seam? Pros cons? 
 

I am concerned that as this roof faces due south, it may not weather very well made from single ply pvc type product.

 

Many thanks,

 

Zoe

[saveasteading]

6 minutes ago, gaschick said:

single ply with a Standing seam

I would say that ply this will work perfectly well without the seams, which are for show to simulate the corrugated appearance.

 

I am surprised it is half the price though so would quotation the material choice.

If it is a high-tech product then good. If a modern equivalent of felt then no.

 

Do you mind indicating the price level?

 

My own preference is for non standing seam metal. I don't mind  the screw heads, and it is usually stronger and with less 'oil canning' effect.

Genuinely half the cost, especially if not by a rolled-on-site supplier.

It is also very much easier to adapt to openings and to seal at any tricky joints.

And if ever damaged, standing seam is not easy to repair/replace.

 

But the screws are the thing....you may not like them.

 

[SimonD]

17 minutes ago, gaschick said:

Our builder has thrown a spanner in by suggesting that instead of the metal standing seam we should use a single ply roofing material with a ‘standing seam’ effect. This is approximately half the cost of the metal option. 
 

Has anyone had experience of using single ply with a Standing seam? Pros cons? 
 

I am concerned that as this roof faces due south, it may not weather very well made from single ply pvc type product.

 

Compared to Greencoat PLX, a single ply standing seam effect roof will look cheap and fake. I also suspect it won't come with a 50 year functional guarantee that you get from Greencoat, with a much longer potential life span if it's then maintained.

 

I suspect your builder is just reflecting a lack of experience with standing seam and going with something that seems easier - easier for him - rather than for the overall benefit of your house.

 

With a 13 degree pitch, there is no problem at all with penetrations within the standing seam. Yes, they take a bit of time, but nothing to phase an experience standing seam installer.

 

Before making a decision, go and have a look a the fake standing seam solution and then go and have a look at some proper real installatios and then make up your mind.

 

31 minutes ago, gaschick said:

The timber frame suppliers will be putting OSB on top.

 

Hold up a little bit here. While osb is okay, the preference for a metal standing seam roof is 1 sarking, 2 plywood. Sarking provides better ventilation to the back of the steel roof, plywood for convenience and good nail pull out resistance for the fixings.

 

OSB does not have great pull out resistance for the nails used by your traditional metal roofing contractor, and screws are much preferred. This adds to time and cost.

 

At the moment, you can get plywood for pretty much the same price as the osb.

 

Talk to you roofing contractor before the tf supplier completes this part of the build.

 

Also double check the roof buildup. Is it a cold roof with ventilation between insulation and final osb or is it a warm roof? Again, if it's warm, make sure you get your roofing contractor in asap to ensure it's all detailed correctly.

 

10 minutes ago, saveasteading said:

it is usually stronger and with less 'oil canning' effect.

 

10 minutes ago, saveasteading said:

It is also very much easier to adapt to openings and to seal at any tricky joints.

 

I don't think either of these statements are true re traditional standing seam roof. A recent discussion here on BH re rooflights installed in a non standing seam metal roof attests to this. Also, a traditional standing seam roof installed well will outlast most if not all the non-standing seam roofs on the market and with completely hidden fixings you're never going to have a weakness of deteriorating screw fixings, which is pretty much guaranteed and well known.

 

Oil canning effect can be due to several issues, but you can reduce this risk by using narrower seam and other methods, but on most installs by a good contractor, this isn't a problem.

[markc]

I have seen a fake standing seam done with Sarnafil (think that’s the right term or spelling) for the waterproof membrane and it was really good. Does not dent or distort with heat or nearby trees/ birds dropping things onto it. Easy to walk on and clean.

we didn’t fit it but was interested because we used to erect a lot of the big fabric tensioned roof structures

[Ralph]

Like everything else, a lot depends on who fits it. I did not like Sarnafil because you can get odd bits like this. On a high roof it may well look fine. 

 

One thing about metal standing seam is you will probably get some level of oil canning. Ours can look perfect on some days then the next the light catches it or it's hot and you can see slight waves. Ours is subtle and I don't mind it. I have been told that a lot of the ones you see online have been photoshoped to remove imperfections.

 

 

 

[JohnMo]

We have Sansfil also.  Should only be installed by qualified person, which is a plus.

 

Use exterior grade 18mm ply instead of OSB.  Sanafil sits on a flease and is screwed on to the ply with spreader plates and the overlapping seam, which covers the screws is hot air welded.  Standing seams are then welded to the membrane, set the spacing so a standing seam covers any joints.

 

Our roof is 12 degs so you will see the effect.

[gaschick]

5 hours ago, saveasteading said:

 

 

I am surprised it is half the price though so would quotation the material choice.

If it is a high-tech product then good. If a modern equivalent of felt then no.

 

Do you mind indicating the price level?

 

My own preference is for non standing seam metal. I don't mind  the screw heads, and it is usually stronger and with less 'oil canning' effect.

Genuinely half the cost, especially if not by a rolled-on-site supplier.

It is also very much easier to adapt to openings and to seal at any tricky joints.

And if ever damaged, standing seam is not easy to repair/replace.

 

But the screws are the thing....you may not like them.

 

Hi @saveasteading 

Builder looking at Sarnafil  standing seam effect £3780+VAT

Standing seam £7164 +VAT

 

WRT the visuality of the roof, the upstairs bedroom window, and landing windows will look down on this. I will try to upload the roofing plans.

@SimonD the builder is getting specialist contractors in for the roof, so not fitting himself and was looking at Sarnafil. As we passed planning with a standing seam roof, I think that Building Control might say something...

 

 

[gaschick]

6 hours ago, saveasteading said:

 

 

I am surprised it is half the price though so would quotation the material choice.

If it is a high-tech product then good. If a modern equivalent of felt then no.

 

Do you mind indicating the price level?

 

My own preference is for non standing seam metal. I don't mind  the screw heads, and it is usually stronger and with less 'oil canning' effect.

Genuinely half the cost, especially if not by a rolled-on-site supplier.

It is also very much easier to adapt to openings and to seal at any tricky joints.

And if ever damaged, standing seam is not easy to repair/replace.

 

But the screws are the thing....you may not like them.

 

Hi @saveasteading 

Builder looking at Sarnafil  standing seam effect £3780+VAT

Standing seam £7164 +VAT

 

WRT the visuality of the roof, the upstairs bedroom window, and landing windows will look down on this. I will try to upload the roofing plans.

@SimonD the builder is getting specialist contractors in for the roof, so not fitting himself and was looking at Sarnafil. As we passed planning with a standing seam roof, I think that Building Control might say something if we changed the look of the roof now... p.s. we are in a very rural agricultural area.

 

 

 

Edited February 24, 2022 by gaschick

[markc]

Sarna will never look as crisp as zinc or any other metal but is much quieter in the rain and very durable

Edited February 24, 2022 by markc

[saveasteading]

7 hours ago, SimonD said:

I don't think either of these statements are true re traditional standing seam roof

My experience is with huge roofs, The main point was the very substantial extra cost for secret fix, but was not noticeable, then you cut holes in it which really are difficult to seal. BUT this was self-spanning between purlins, and  so maybe is different for small scale and screwed to wood.

 

1 hour ago, gaschick said:

Builder looking at Sarnafil  standing seam effect £3780+VAT

Standing seam £7164 +VAT

 

25m2 of roof without deducting skylights, and 35m of edges to form?

 

For profiled cladding my keen (perhaps optimistic) estimate would have been 25m2  x £35, + 35mx  £15,  so about £2,500 plus access and perhaps an extra margin for the main contractor.  £3k to £3.5k approx.

Similar cost for Sarnafil (but I am totally guessing) as there is no waste and edges are easier.

Standing seam,  add at least 50%? 

 

BUT this is dependant on finding skilled workers interested in this small job. Do not let anyone practice on your roof: metal cladding is highly skilled, and should not depend on tubes of mastic as it often ends up with beginners.

 

You are even turning me towards considering Sarnafil for ours.....we will see what skills are available nearer the time. Building inspector won't mind (but tell them), your planners/neighbours  might.

 

 

 

 

[SimonD]

3 hours ago, gaschick said:

the builder is getting specialist contractors in for the roof, so not fitting himself and was looking at Sarnafil. As we passed planning with a standing seam roof, I think that Building Control might say something if we changed the look of the roof now... p.s. we are in a very rural agricultural area.

 

Looking at your drawings, they correctly specify the use of WBP Plywood as the substrate for the standing seam roof. If you do decide to go ahead, make sure your tf builder complies with this specification and doesn't use osb. The spec on the drawings is correct for the standing seam with a ventilated cold roof.

 

As it's a change of material, you may be correct in that it might require an amendment to the planning approval - are there any conditions?

 

You will notice the difference between standing seam and whatever the lookalike version is called, especially if you're looking down on it from a window above. Best thing as always is to see if you can look at some local installations to make a comparison and therefore more informed personal decision.

 

1 hour ago, saveasteading said:

BUT this was self-spanning between purlins, and  so maybe is different for small scale and screwed to wood.

 

Yeah, a big difference there! ?

 

[gaschick]

30 minutes ago, SimonD said:

 

Looking at your drawings, they correctly specify the use of WBP Plywood as the substrate for the standing seam roof. If you do decide to go ahead, make sure your tf builder complies with this specification and doesn't use osb. The spec on the drawings is correct for the standing seam with a ventilated cold roof.

Thank you @SimonD I will double check the specification from the TFM when I get home. 

30 minutes ago, SimonD said:

 

As it's a change of material, you may be correct in that it might require an amendment to the planning approval - are there any conditions?

Not as far as we know for planning conditions. The only people that will see the top of the roof will be us. It's not visible from our neighbours.

 

30 minutes ago, SimonD said:

 

You will notice the difference between standing seam and whatever the lookalike version is called, especially if you're looking down on it from a window above. Best thing as always is to see if you can look at some local installations to make a comparison and therefore more informed personal decision.

 

 

Yeah, a big difference there! ?

 

The builders have used a qualified Sarnafil contractor before for another job