comparative costings between slates and standing seam roof

[scottishjohn]

as per title ,thinking to when I get to rebuild the big house,

when planning finally give decision  etc

is there much difference in costings between the two systems .assuming roof is same construction 

sarking boards and roof membrane 

 

 I,m just finishing rebuilding my old explosive shed  with slates --

had to rebuild the gables in stone and make up roof frame work - more new skills learnt 

walls are 500m thick on a building which is only just over 3.2m long  2.8 wide externally

that will be the she shed

 

 

Edited September 18, 2021 by scottishjohn

[Stones]

From what I remember when I looked, it was less than slate, but a lot more than concrete tile.  One of the installation details was it had to be laid on 18mm board and breather membrane.  Also depends on the roof, the sq m price of the sheeting seems reasonable but the cost of flashings adds up.

[Arnewhouse]

Having just fitted both standing seam and slate to our house I would say slate (if going for spanish) would be less costly. The build up under the standing seam required more OSB as we had a build up from the rafters up of 9mm osb, breathable membrane,  battens, 18mm osb, membrane for under standing seam and the finally standing sheets themselves. 

[Lorenz]

I find it strange, I was in Latvia for 8 years and this standing seam is the cheapest option, even less than the stick on shingles. Why is it so in and so expensive in the UK, when it is the cheapest in most of northern europe?

[saveasteading]

Intuitively, metal cladding is much cheaper than slate, or even good tiles, with standing seam somewhere between.

 

However:

Metal cladding gets tricky at diagonal cuts, and there is also a lot of cutting waste (unless you are very clever with lengths and cutting schedule)

 

For a small job, the delivery on cladding can be disproportionately high too, as it needs palletising and gash cover sheets.

Beware of agricultural quality.

 

2 hours ago, Arnewhouse said:

9mm osb, breathable membrane,  battens, 18mm osb, membrane for under standing seam and the finally standing sheets

 

I am not understanding the need for 2 sheets of osb and battens.

I would spec: osb, breather membrane, battens, metal sheet.

[Lorenz]

Where I was the ready made trays were cheap but the rolls worked out better in use, cannot imagine much waste from the roll.

[SimonD]

5 hours ago, scottishjohn said:

sarking boards and roof membrane

 

Assuming you'll be using traditional sarking boards at 22mm thickness these are fine for a standing seam roof. Just make sure that if you do go for the standing seam you use a marginally thinner sarking board at the eaves for the eaves flashing.

 

With traditional standing seam it's often the labour that's expensive and this will depend on the number of penetrations in the roof and its shape. If it's a simple rectangular shape, it's a really straight forward and quick process. You can even buy ready fabricated trays that clip together saving even more on labour.

 

I've installed both and love both materials, but I think my personal preference does now lean towards the metal.

Edited September 18, 2021 by SimonD

[saveasteading]

1 hour ago, Lorenz said:

cannot imagine much waste from the roll.

If there is a hip, then the sheet is cut on the diagonal to fit, and the triangle is thrown away. Also is a tricky cut, (with a nibbler or shears) to avoid mistakes.

So say there is a hip-end, then every sheet is cut and has wastage, unless you can flip it over and use the cut angle on the opposite hip...in my experience the cladder has to be told exactly how to cut every sheet, otherwise the old habit of a new sheet every time comes in.

 

With slates and tiles the same angled cuts exist but the wastage is a small fraction.

 

also metal sheets have to be quite precisely ordered, to fit just over the gutter and under the ridge.   For  a big roof it may be that 2 sheets are used, and then they overlap.

Tiles take away that risk and precision.

 

summary...for a big roof i think metal is much cheaper in material and labour.

For a small roof tiles/slates, and you would struggle to find a metal cladder anyway.

 

 

[Arnewhouse]

9 hours ago, saveasteading said:

I am not understanding the need for 2 sheets of osb and battens.

I would spec: osb, breather membrane, battens, metal sheet.

The reason that the standing seam was laid on another solid layer (osb) and not battens was to prevent rippling of the sheets. 

[scottishjohn]

19 hours ago, saveasteading said:

If there is a hip, then the sheet is cut on the diagonal to fit, and the triangle is thrown away. Also is a tricky cut, (with a nibbler or shears) to avoid mistakes.

So say there is a hip-end, then every sheet is cut and has wastage, unless you can flip it over and use the cut angle on the opposite hip...in my experience the cladder has to be told exactly how to cut every sheet, otherwise the old habit of a new sheet every time comes in.

 

With slates and tiles the same angled cuts exist but the wastage is a small fraction.

 

also metal sheets have to be quite precisely ordered, to fit just over the gutter and under the ridge.   For  a big roof it may be that 2 sheets are used, and then they overlap.

Tiles take away that risk and precision.

 

summary...for a big roof i think metal is much cheaper in material and labour.

For a small roof tiles/slates, and you would struggle to find a metal cladder anyway.

 

 

If design stays as it is then 

the building is "L" shaped with one hip

main roof will be 22m long and width of building is 8m

hip section will be approx 8m

long and 7m wide 

Edited September 19, 2021 by scottishjohn

[scottishjohn]

On 18/09/2021 at 08:39, Stones said:

From what I remember when I looked, it was less than slate, but a lot more than concrete tile.  One of the installation details was it had to be laid on 18mm board and breather membrane.  Also depends on the roof, the sq m price of the sheeting seems reasonable but the cost of flashings adds up.

what I used on shed are 100year warranty ones --they are £1 each -so similar to concrete tiles  in price .

certainly worth a deeper investigation 

 done one side with the reclaimed 200 year old cast iron roof light 

too wet to do other  side today  for me -which has no penetrations

Edited September 19, 2021 by scottishjohn

[saveasteading]

1 hour ago, scottishjohn said:

laid on 18mm board and breather membrane.

Metal cladding should not sit on a surface that could be wet. I'm not going to stress my brain today into thinking if that could be wet on the underside, but gut feeling says yes, condensation.

so battens of timber or galv needed.

 

To answer another matter above, every single steel shed you see has purlins (Z rails) on the roof, with cladding spanning somewhere between 1 and 2 m according to the sheet strength. It  does not need to sit on a board.

[SimonD]

21 hours ago, saveasteading said:

If there is a hip, then the sheet is cut on the diagonal to fit, and the triangle is thrown away. Also is a tricky cut, (with a nibbler or shears) to avoid mistakes.

So say there is a hip-end, then every sheet is cut and has wastage, unless you can flip it over and use the cut angle on the opposite hip...in my experience the cladder has to be told exactly how to cut every sheet, otherwise the old habit of a new sheet every time comes in.

 

2 hours ago, scottishjohn said:

If design stays as it is then 

the building is "L" shaped with one hip

main roof will be 22m long and width of building is 8m

hip section will be approx 8m

long and 7m wide 

 

I'm not sure of you're talking cross purposes here. The issue with the hip on a traditional fully supported standing seam roof isn't as described above because you would simply form shorter trays from the coil to account for the effective roof length. Indeed, this would also be done if you were ordering prefabricated standing seam sheets as you'd pull the required measurements off the as built roof. You wouldn't experience the same wastage compared to a standard length corrogated metal roof sheet, nor would you experience problems cutting each tray to fit the angle of the hip ridge - this is bread and butter for a standing seam contractor and is very easy to do.

 

2 hours ago, scottishjohn said:

For  a big roof it may be that 2 sheets are used, and then they overlap.

 

On traditional stending seam, there is not overlap. The coils are sold in certain widths which can be specified, the most commog being a cover between seams of 430mm, 530mm and 600mm, with corresponding coild widths of 500, 600 and 670 for 25mm standing seams.

 

On 18/09/2021 at 11:32, saveasteading said:

I would spec: osb, breather membrane, battens, metal sheet.

 

Not on a traditional standing seam roof. This requires the metal to be fully supported. However, I do wonder about the necessity of this buildup

 

On 18/09/2021 at 09:03, Arnewhouse said:

9mm osb, breathable membrane,  battens, 18mm osb, membrane for under standing seam and the finally standing sheets

 

I think the roofers could easily have left out the 9mm osb and first layer of breather membrane unless they were worried about wind wash on the insulation where membrane would be sensible. Otherwise, it's absolutely the correct buildup with 18mm supporting osb and membrane under the steel roof.

 

 

5 minutes ago, saveasteading said:

Metal cladding should not sit on a surface that could be wet. I'm not going to stress my brain today into thinking if that could be wet on the underside, but gut feeling says yes, condensation.

so battens of timber or galv needed.

 

To answer another matter above, every single steel shed you see has purlins (Z rails) on the roof, with cladding spanning somewhere between 1 and 2 m according to the sheet strength. It  does not need to sit on a board.

 

This is not correct, you're talking different a different roof finish compared to a standing seam roof which does require support, unless the OP has got the terms confused?

[saveasteading]

55 minutes ago, SimonD said:

You wouldn't experience the same wastage compared to a standard length corrugated metal roof sheet

Then don't use standard lengths.

If you schedule and have them rolled to order then there is no waste in the length, only in the site cutting of the  triangles ., and that applies to coil rolled on site too. 

 

Rather different if you had bought lots of oversized or 'standard' lengths from the local merchant.

 

Perhaps the coil people take away all the bits, and then it is not apparent.

Not everyone, including cladders, is necessarily skilled at measuring for scheduling, so I can see the attraction  of rolling on site

 

I also appreciate that the specialists with a coil on the lorry will have the benefit of revising the lengths as they go along,, if some adjustment is needed,

 

 

1 hour ago, SimonD said:

traditional standing seam roof.

I only know about commercial details, and they always span between purlins.  I can't see the benefit of sitting on boards, unless the cladding is very weak and cannot self-support, but 

perhaps coil cladding for housing is weak...let's find out. This could be what happens when a traditional house build takes on new materials and a new detail is not perfected. Perhaps there is a published detail by one of the big cladding manufacturers.

 

1 hour ago, SimonD said:

a standing seam roof does require support,

Maybe it does for housing, I need to find out. Standing seam is used on commercial roofs spanning between purlins, and the area used successfully is probably hundreds of times that used for housing. Perhaps it is much stronger, using thicker metal, higher grade metal  and deeper profile.

 

I need to find out as am currently considering not putting the slates back on, and using metal.

Not necessarily standing seam which has benefits and also challenges (including cost)

 

It seems that throughout this discussion 'standing seam' is being applied only to the specialists who roll coil on site and then fix. I can see that might be expensive and so traditional methods can compete.

It is available to buy and fix yourself.

 

I am more likely to price the project on  bought sheets, screw-fixed to rails, and so missing out a few margins along the way.

 

In the Highlands I have seen a lot of Ondulit, and traditional corrugated , plastisol steel profiles on conversions and some new-builds. This is quite cheap, but looks rather agricultural....which may be appropriate to location.

I will be considering a flatter profile, 900 or 1000 cover, with crowns at 300 or 333. I don't mind seeing a few screws....what you can see you can fix, and they can be replaced if damaged.

 

[SimonD]

3 hours ago, saveasteading said:

I only know about commercial details, and they always span between purlins.  I can't see the benefit of sitting on boards, unless the cladding is very weak and cannot self-support, but 

perhaps coil cladding for housing is weak...let's find out. This could be what happens when a traditional house build takes on new materials and a new detail is not perfected. Perhaps there is a published detail by one of the big cladding manufacturers.

 

No they don't. There are plenty of very large commercial projects using what I explained was a traditional fully supported standing seam roof. There are plenty of published details. I personally have a copy of the Federation of Traditional Metal Roofing Contractors Guide to Good Practice because I've installed this type of roof.

 

3 hours ago, saveasteading said:

Standing seam is used on commercial roofs spanning between purlins, and the area used successfully is probably hundreds of times that used for housing. Perhaps it is much stronger, using thicker metal, higher grade metal  and deeper profile.

 

The fully supported traditional standing seam roof is used both for commercial and domestic purposes and has been for decades, if not more than 100 years, more widely outside of the UK. As I think I said, we're talking different products designed for different build systems. For a domestic project, you're unlikely to get any supplier to sell you the systems used for this kind of commercial project, because it's not worth their while due to the normal size of project.I spoke to a few for my current project and the closest I got from one of them was an indication that I might get some offcuts from an airport development.

 

Typically the commercial standing seam roofs I think you are refering to have a much higher upstand, but you'll find they're similar thicknesses to slightly thicker at about 0.7 - 1.2mm. They tend to have a narrower cover at about 400mm or just over IIRC. They also often consist of a sandwich construction with double layers of steel-  corrugated below as a structural deck, insulation, and then the standing seam (e.g. Kingspan). I've come across one traditional standing seam product by Euroclad (basically Tata Steel Colourcoat Urban), that can apparently be installed just on battens, but in this case, I'd be concerned maintenance access would be severely compromised.

 

3 hours ago, saveasteading said:

Maybe it does for housing, I need to find out

 

The fundamental fact is that the OP asked whether sarking boards and breather membrane were satisfactory for supporting a traditional standing seam roof and the answer is that yes they are. Sarking boards are actually preferred to osb and plywood as a substrate because they provide better through ventilation to the back of the metal. Plywood is the popular installers choice because it has good pull out strength for nails which reduces installation time and osb is third because of reduced fixing pull out strength, so you either have to increase the number of fixings or use screws instead of nails in high wind uplift areas.

 

Edited September 19, 2021 by SimonD