Why are roofs on new builds made out of wood and not steel?

v638sg7k1a92bx

Is it purely down to cost? Seems that steel is so much more sturdy than wood and that roofs are prone to problems why are roofs on new builds not made out of steel?
New houses being built on our road and the roof is al made out of timber.

cnocbui

Cost: both the material and the labour required to work with it.

Mellor

Anaya Sticky Self-portrait wrote: »

Is it purely down to cost? Seems that steel is so much more sturdy than wood and that roofs are prone to problems why are roofs on new builds not made out of steel?
New houses being built on our road and the roof is al made out of timber.

Steel is no more sturdy than wood. The strength of each is down to the size of the member. Steel roofs are prone to same problems.

Attics are generally not floored, which suits timber joints more than steel.

v638sg7k1a92bx

Mellor wrote: »

Steel is no more sturdy than wood. The strength of each is down to the size of the member. Steel roofs are prone to same problems.

Attics are generally not floored, which suits timber joints more than steel.

So why are sky scrapers not made out of timber?

Can steel get woodworm and dry rot?

Will the trusses in an steel roof bow like a timber one?

Lumen

Wood is a reasonable insulator, whereas steel is terrible, so it is more difficult to avoid cold bridges and interstitial condensation, which is as bad for steel as it is for wood.

I think you're on to something with the skyscrapers. You should patent timber reinforced concrete before someone else does.

dathi

Lumen wrote: »

Wood is a reasonable insulator, whereas steel is terrible, so it is more difficult to avoid cold bridges and interstitial condensation, which is as bad for steel as it is for wood.

I think you're on to something with the skyscrapers. You should patent timber reinforced concrete before someone else does.

https://www.treehugger.com/green-architecture/worlds-tallest-timber-tower-topped.html
to late for that

Mellor

Anaya Sticky Self-portrait wrote: »

So why are sky scrapers not made out of timber?

Can steel get woodworm and dry rot?

Will the trusses in an steel roof bow like a timber one?

Because the size of timbers are limit by the size of trees. They are also less space efficient for a given strength. Neither of those factors are relevant in domestic construction. I'd have thought that was fairly obvious.

No steel doesn't rot or get worm. Both of which are preventable.
On the other hand timber doesn't corrode or rust, steel does. Also preventable.

Lightweight Steel trusses move more than timber actually.
Steel is much more susceptible to movement due to temperature changes. This movement is a significant concern in steel roofs.

listermint

I don't know of any problems with wood in roofs on new houses ??


The ones in mine are over 40 years old.

jack of all

All well answered above, but steel and condensation is a corrosion risk. Light steel sections can fail spectacularly in (even a small) fire situation.

listermint

listermint wrote: »

I don't know of any problems with wood in roofs on new houses ??


The ones in mine are over 40 years old.

I nearly bought a 200 year old house once and the timber roof was the only thing not wrote off!
Beautiful craftsmanship too.

v638sg7k1a92bx

Mellor wrote: »

Because the size of timbers are limit by the size of trees. They are also less space efficient for a given strength. Neither of those factors are relevant in domestic construction. I'd have thought that was fairly obvious.

No steel doesn't rot or get worm. Both of which are preventable.
On the other hand timber doesn't corrode or rust, steel does. Also preventable.

Lightweight Steel trusses move more than timber actually.
Steel is much more susceptible to movement due to temperature changes. This movement is a significant concern in steel roofs.

Can we please stop with these type of nonsense answers. Are we in artic circle or Sahara desert?

Markcheese

Anaya Sticky Self-portrait wrote: »

Can we please stop with these type of nonsense answers. Are we in artic circle or Sahara desert?

Have you ever been in an attic on a sunny day ? It'd cook you ,!!! ,mind you ,doesn't cause much problem in northern Australia,where it tends to be about termites ( Our winter temp are pretty mellow all right )
I dare say if you want a steel roof you could have one ,

muffler

Anaya Sticky Self-portrait wrote: »

So why are sky scrapers not made out of timber?

Can steel get woodworm and dry rot?

Will the trusses in an steel roof bow like a timber one?

I may as well ask why wheels arent square. :rolleyes:

Mellor

Anaya Sticky Self-portrait wrote: »

Can we please stop with these type of nonsense answers. Are we in artic circle or Sahara desert?

They are the answers to the nonsense questions you are asking.
I mean, you are wondering why skyscrapers are not made of timber. Clueless stuff.

I've no idea what you are on about with Artic circle. Ireland varies more in temp that the artic circle.

In a country with varying levels of wind, wood, which flexes is preferential over a rigid material like steel that doesn't flex.

A sharp gust against a rigid steel roof will lift the roof off, whereas a wooden roof in the same conditions would bend and flex and divert the wind away and stay in place.

Victor

Horses for courses - weight, cost and workability.

While steel is high strength, it is dense. To achieve the structure needed for a roof, the members would need to be disproportionately large and / or frequent, likely resulting in a roof that is overall heavier than a timber roof.

Steel is expensive.

It is difficult to work steel and can be prohibitively expensive to do so on site. It's a lot easier to cut 10mm off a piece of timber than to do it to steel. Similarly, if the holes in 2 pieces of steel don't line up, you're stuck.

Now, that said, if you want to build a building with large spans, e,g. a warehouse, steel is very useful.

Skyscrapers use steel more than timber because steel has a higher density and compressive strength.

hesker

Timber is a renewable resource.

Lumen

hesker wrote: »

Timber is a renewable resource.

So is steel!

hesker

Lumen wrote: »

So is steel!

Do you mean recyclable

Lumen

hesker wrote: »

Do you mean recyclable

You're right, I was sloppy with wording.

I suppose what I meant was "sustainable", in the sense that both timber and steel can be responsibly produced and recycled so as to cause minimal environmental damage.

In practice, it's way more complicated.

Ireland's spruce infection, for instance, is simplistically sustainable but ecologically grim.

And once you start assembling structures from timber you end up using nasty plastics, resins and preservatives to give the required performance characteristics (glulam, lvl, plywood, membranes, copper biocides...).

I am a big fan of timber and steel structures though. You can't get very far in a wood structure without steel.

v638sg7k1a92bx

muffler wrote: »

I may as well ask why wheels arent square. :rolleyes:

That would be a stupid question.

v638sg7k1a92bx

Victor wrote: »

Horses for courses - weight, cost and workability.

While steel is high strength, it is dense. To achieve the structure needed for a roof, the members would need to be disproportionately large and / or frequent, likely resulting in a roof that is overall heavier than a timber roof.

Steel is expensive.

It is difficult to work steel and can be prohibitively expensive to do so on site. It's a lot easier to cut 10mm off a piece of timber than to do it to steel. Similarly, if the holes in 2 pieces of steel don't line up, you're stuck.

Now, that said, if you want to build a building with large spans, e,g. a warehouse, steel is very useful.

Skyscrapers use steel more than timber because steel has a higher density and compressive strength.

Cost of timber is not that much different from steel atm.

GreeBo

Deleted User wrote: »

A sharp gust against a rigid steel roof will lift the roof off, whereas a wooden roof in the same conditions would bend and flex and divert the wind away and stay in place.

Ha?

Can you elaborate on this a bit?
Are you maybe confusing a steel clad roof with a tiles/slate roof?
The OP is about the structure of the roof, not the finish.

Victor

It would take an extreme event, but if something is too rigid, with no give, it can break instead of flexing. You could still make it rigid, but you would have to use more material than you would need otherwise.

Due to their relative lightness, most roof coverings will flex somewhat. If the structure is too rigid, there will be a variation in the flexing between roof covering and structure. Over time, this could loosen joints, fixings, etc.

Crumple zones in cars would be another example, although not quite the same. The crumple zone distorts, so the passenger compartment doesn't.

GreeBo

Victor wrote: »

It would take an extreme event, but if something is too rigid, with no give, it can break instead of flexing. You could still make it rigid, but you would have to use more material than you would need otherwise.

Due to their relative lightness, most roof coverings will flex somewhat. If the structure is too rigid, there will be a variation in the flexing between roof covering and structure. Over time, this could loosen joints, fixings, etc.

Crumple zones in cars would be another example, although not quite the same. The crumple zone distorts, so the passenger compartment doesn't.

Yeah I understand that, but I fail to see how timber trusses and joists would fair any better than steel in the scenarios you are talking about.

Steel flexes too and if timber flexes more, then that's asking for trouble where the roof meets the house surely?
Also the main goal is to keep the roof attached to the house in those extreme conditions, the stronger the structure the better imo!

The #1 reason is cost, both of materials and time to work with.

Mellor

Anaya Sticky Self-portrait wrote: »

That would be a stupid question.

exactly.

Victor wrote: »

Due to their relative lightness, most roof coverings will flex somewhat. If the structure is too rigid, there will be a variation in the flexing between roof covering and structure. Over time, this could loosen joints, fixings, etc.

What sort of roof covering/structure are you describing?

Tiles and slats for example are relatively heavy, and very rigid. They are fied in a way that allows movement between members, so that it copes with deflection in the structure (whether it is timber or steel). But there is no additional flex in the lining other than the structure.

The idea that steel is rigid and won't flex is simply not the case.

v638sg7k1a92bx

A lot of chipping and changing and cutting goes on with timber roof. Steel just slots into place.

Bonzo Delaney

Anaya Sticky Self-portrait wrote: »

A lot of chipping and changing and cutting goes on with timber roof. Steel just slots into place.

Maybe check twice cut once

Mellor

Anaya Sticky Self-portrait wrote: »

A lot of chipping and changing and cutting goes on with timber roof. Steel just slots into place.

Not really.
A prefab timber truss goes straight up, so does a prefab steel truss.
If you have to chop and change either, then you have messed up somewhere.

Obvious a timber cut roof is cut and measured on site. But so too would a steel cut roof be. You have to compare like with like.

maestroamado

Mellor wrote: »

Not really.
A prefab timber truss goes straight up, so does a prefab steel truss.
If you have to chop and change either, then you have messed up somewhere.

Obvious a timber cut roof is cut and measured on site. But so too would a steel cut roof be. You have to compare like with like.

The design of trusses means they cannot be chopped as the strength is in the design to spread the weight directly downward on walls.


Steel truss roofs are used for industry, factories and sheds.
I have not seen steel roof in houses...

Lumen

I'm not sure why more gabled houses don't use a steel ridge beam (and steel king posts,, if the house is otherwise timber framed), plus external (to the load bearing structure) roof insulation.

It solves the wall spreading issue without the need for ties, so had the potential to great incredible vaulted spaces, keep MHRV services inside the envelope etc.

GreeBo

Lumen wrote: »

I'm not sure why more gabled houses don't use a steel ridge beam (and steel king posts,, if the house is otherwise timber framed), plus external (to the load bearing structure) roof insulation.

It solves the wall spreading issue without the need for ties, so had the potential to great incredible vaulted spaces, keep MHRV services inside the envelope etc.

I was in a rented house in Stepaside for a few months, A rated and built probably in the last 5 years and it had a mixture of steel beams and timber in the attic. It was a cold space though and not really vaulted, so not sure why, but to be fair I didnt really investigate.

maestroamado

GreeBo wrote: »

I was in a rented house in Stepaside for a few months, A rated and built probably in the last 5 years and it had a mixture of steel beams and timber in the attic. It was a cold space though and not really vaulted, so not sure why, but to be fair I didnt really investigate.

In recent years there is steel beam going from gable to gable.
It used be 9"x3" wood but it seems to have changed.
I assume the reason its cold it well isulated so heat stays in the house....

v638sg7k1a92bx

Mellor wrote: »

Not really.
A prefab timber truss goes straight up, so does a prefab steel truss.
If you have to chop and change either, then you have messed up somewhere.

Obvious a timber cut roof is cut and measured on site. But so too would a steel cut roof be. You have to compare like with like.

When I was in Oz an NZ we worked on refurbs and renovations and it was always a steel roof cut and measured offsite and lifted in by a crane - no cutting, copping, changing but In Ireland we seem to complicate the whole issue, "oh we don't do it that way over here" "timber is just as good" "that wouldn't work over here"

Lumen

Anaya Sticky Self-portrait wrote: »

When I was in Oz an NZ we worked on refurbs and renovations and it was always a steel roof cut and measured offsite and lifted in by a crane - no cutting, copping, changing but In Ireland we seem to complicate the whole issue, "oh we don't do it that way over here" "timber is just as good" "that wouldn't work over here"

NZ has earthquakes. I've no idea whether that explains the difference, but I wouldn't assume that we are doing it wrong just because we are doing it differently.

Americans talk about "20 and 30 year roofs". For them the roof is almost a consumable part. Is that wrong? I don't know. Presumably it works for them.

Mellor

Anaya Sticky Self-portrait wrote: »

When I was in Oz an NZ we worked on refurbs and renovations and it was always a steel roof cut and measured offsite and lifted in by a crane - no cutting, copping, changing but In Ireland we seem to complicate the whole issue, "oh we don't do it that way over here" "timber is just as good" "that wouldn't work over here"

If it’s constructed off-site and lifted in by crane it’s a prefab truss not a cut roof. You are getting two different things mixed up.
A preference for steel in NZ is possibly driven by earthquakes.

In Australia, both steel and timber prefab trusses are used, but timber cut roofs are by far the most common. Timber framed houses are, in general, more common than in Ireland. They wouldn’t use brick/block cavity as much.

Steel studs are more common in commercial scale steel/concrete framed buildings however.

v638sg7k1a92bx

Mellor wrote: »

If it’s constructed off-site and lifted in by crane it’s a prefab truss not a cut roof. You are getting two different things mixed up.
A preference for steel in NZ is possibly driven by earthquakes.

In Australia, both steel and timber prefab trusses are used, but timber cut roofs are by far the most common. Timber framed houses are, in general, more common than in Ireland. They wouldn’t use brick/block cavity as much.

Steel studs are more common in commercial scale steel/concrete framed buildings however.

Don’t get me started on the studs. I can’t understand how steel studs are not standard in all buildings. When I would see timber studs going into buildings my stomach would drop.

GreeBo

Anaya Sticky Self-portrait wrote: »

Don’t get me started on the studs. I can’t understand how steel studs are not standard in all buildings. When I would see timber studs going into buildings my stomach would drop.

When i see steel studs going in I'm more worried that my flat screen tv will drop.

GreeBo

Lumen wrote: »

NZ has earthquakes. I've no idea whether that explains the difference, but I wouldn't assume that we are doing it wrong just because we are doing it differently.

Americans talk about "20 and 30 year roofs". For them the roof is almost a consumable part. Is that wrong? I don't know. Presumably it works for them.

Yeah, the US has a huge industry around re-roofing, but I thought that was typically around the shingle side of things and maybe the sheathing if the last guy botched the shingles but that it wasnt at all about the roof structure itself.

v638sg7k1a92bx

GreeBo wrote: »

When i see steel studs going in I'm more worried that my flat screen tv will drop.

First world problems there Bo, you need to check your privilege.

Mellor

maestroamado wrote: »

The design of trusses means they cannot be chopped as the strength is in the design to spread the weight directly downward on walls.

I missed this one yesterday. I haven't suggested trusses work any other way.

Anaya Sticky Self-portrait wrote: »

Don’t get me started on the studs. I can’t understand how steel studs are not standard in all buildings. When I would see timber studs going into buildings my stomach would drop.

I'm a big fan of steel studs for commercial construction. Fast, strong and very good acoustically. However they don't handle twisting, or offset loads as well. So less future adaptable in residential.

GreeBo wrote: »

When i see steel studs going in I'm more worried that my flat screen tv will drop.

TVs are getting lighter. By current TV is supported on a steel furring channel and plasterboard lining without issued. But the bracket is very good.

Heavier TVS are fine as long as you know in advance where that are going, and the wall is braced.

GreeBo

Mellor wrote: »

TVs are getting lighter. By current TV is supported on a steel furring channel and plasterboard lining without issued. But the bracket is very good.

Heavier TVS are fine as long as you know in advance where that are going, and the wall is braced.

Yeah but that is kinda the point. Who knows what will go where in 5 years time.
Right now you find a stud and stop worrying, with metal studs it's not so simple.

100% agree that they have their uses, typically commercial where the wall can be short-lived and there is control over the loads placed on the wall.

Mellor

GreeBo wrote: »

Yeah but that is kinda the point. Who knows what will go where in 5 years time.
Right now you find a stud and stop worrying, with metal studs it's not so simple.

I get that completely, but it’s down to the right fixings not timber vrs steel.
As I said, I’ve a TV, 60” hung off plasterboard and fittings with the right fixing.
And i’ve seen bigger without issue.

The main concern is the kitchen units and the sex swing

Yellow_Fern

It is worth pointing out that the use of steel is creeping in. from factory assembled trusses to RSJs on gables and easi joists steel is increasingly being used for roofs and floors.

v638sg7k1a92bx

Yellow_Fern wrote: »

It is worth pointing out that the use of steel is creeping in. from factory assembled trusses to RSJs on gables and easi joists steel is increasingly being used for roofs and floors.

That's what I'm saying. In Ireland we latch onto certain ways of doing things e.g. carpets and saddle boards :pac:

Seriously, the main reason is probably because steel is not that much more expensive than timber these days.

theguzman

Timber is good for nothing here in my own opinion it rots far too easily and Ireland has one of the worst miserable climates you can imagine for timber. The softwood crap that they plant here isn't worth a damn, fences and patio decking done during the boom have mainly rotted away now. Farmers on an never-ending journey of fencing with softwood stakes. Oak; the Brown oak is the only wood of any use I would use in structural timber because I am thinking longevity. More Concrete builds and Steel roofs should be encouraged I would say. Irish White Deal Spruce would be perfect for places like Dubai or Saudi Arabia where they are bone dry all the time but not Ireland.

ted1

Anaya Sticky Self-portrait wrote: »

Is it purely down to cost? Seems that steel is so much more sturdy than wood and that roofs are prone to problems why are roofs on new builds not made out of steel?
New houses being built on our road and the roof is al made out of timber.

Wood would be just as sturdy and copes with fire better

ted1

Anaya Sticky Self-portrait wrote: »

Don’t get me started on the studs. I can’t understand how steel studs are not standard in all buildings. When I would see timber studs going into buildings my stomach would drop.

Easier to hang a tv off a wooden stud.

awec

Metal studs are a pain in the arse.

Yellow_Fern

theguzman wrote: »

Timber is good for nothing here in my own opinion it rots far too easily and Ireland has one of the worst miserable climates you can imagine for timber. The softwood crap that they plant here isn't worth a damn, fences and patio decking done during the boom have mainly rotted away now. Farmers on an never-ending journey of fencing with softwood stakes. Oak; the Brown oak is the only wood of any use I would use in structural timber because I am thinking longevity. More Concrete builds and Steel roofs should be encouraged I would say. Irish White Deal Spruce would be perfect for places like Dubai or Saudi Arabia where they are bone dry all the time but not Ireland.

Metal is creeping in to house construction but it has its own problems. Metal is highly conductive and its easy to interupt your thermal envolpe because of this. One remarkably counter intutive but supposedly very effective way to preserve wood is to burn it. Charr the surface and it stops it rotting. Shou sugi ban, check it out.

Mellor

awec wrote: »

Metal studs are a pain in the arse.

They are significantly better on big jobs. For speed, services, and numberous other reasons.
The issue is that have to be detailed properly, and installed properly, neither of which is particularly strong in Ireland. Maybe it's getting better, but in the past they weren;t even mentioning building design/architectural courses. Instead it was all Homebond guide.