Cut vs Trussed roof

Slates

Anyone have an opinion on the way to go with this option ??

I'd say I'll be heading for the trussed option ............

Fingalian

Less usable space in a Truss roof and tricky to convert into room later on. ( should you decide to go down that road)

RKQ

I think it would depend on the area and shape of the roof. Truss roof can be more economical over a wider span, but there isn't much of a price difference really, all things considered. Might need to hire a crane or teleported to lift trusses onto wallplate. Neither required for traditional roof!
The truss is ideal for the developer of large housing estates, as a truss roof can be erected quickly and simply. All houses with the same spans means savings on a bulk order etc.
Less usable space in a Truss roof and tricky to convert into room, is quite correct.

sunnysoutheast

You can get "attic trusses" which lend themselves to easy conversion as they have the relevant room space free of interference.

The cheaper standard trusses are very difficult, if not impossible, to convert later on without replacing the roof.

SSE

Mellor

They are by no means impossible, just harder.
The other side is that attic trusses are easier than a cut roof.

sinnerboy

Slates wrote: »

Anyone have an opinion on the way to go with this option ??

I'd say I'll be heading for the trussed option ............

don't forget to wind-brace them asap

and plan the logistics of the on site installation . overhead cables / crane swing etc

trusses can be ruled out sometimes with tight infill sites .

topcatcbr

Slates wrote: »

Anyone have an opinion on the way to go with this option ??

I'd say I'll be heading for the trussed option ............

Both do esentially the same thing

However if you should ever need to add extra space (often overlooked and regretted later) a cut roof is the preferred option.

Ensure that you get a qualified & experienced (City & Guilds or Senior Trades Cert) carpenter to cut your roof, you'd be surprised how many "roofers" are not qualified.

Standard Fink Type Trusses are about the same cost as a cut roof and in a one off dwelling i can see no real advantage for the client.
They are usually quicker to erect than a cut roof, but what is a few days and you may have to wait on delivery from factory. The ceiling/Floor joist timbers can easily sized up for future development and do not cost that much extra.

Attic (Dormer) Trusses are usually the most expensive and are frequntly used in timberframe construction as the factory is already manufacturing the rest of dwelling.

To conclude
If it is timber frame go for trusses
If not I would advise a cut roof option and allow joist size for future development.

My credentials
4 years apprentice carpenter, 10 years as qualified carpenter.
5 years as qualified architectural tech.

over 20 years in construction.

Supertech

Disagree that they're 'just harder' to adapt mellor .... all the strength in the roof truss is in the triangulation. The strength of the structure is in the entire truss unit and its individual connectors, and therefore the individual components are normally much smaller than rafters / floor joists sized under IS444. You go cutting into the braces on a roof truss and you're leavin yourself with massive potential problems. If its a rectangular plan, with gables and no attic conversion required or foreseen, I'd use trusses - all other instances I'd cut the roof - there's much greater flexibility with that option.

Mellor

Are you saying that its impossible? Because I've seen it done. I maintain its harder, but not impossible.

You don't just cut into the members, you replace the fixed supports.
In a truss, the rafters have to be strong enough to support the slates based on the three support points being fixed. If they are not the rafters fail at the midpoints. If you replace these fixed supports, with rigid purlins then the rafters can remain.

Of course the joist may not be sized for full loading, but that can also happen in a cut roof, floor verses ceiling loading.

Supertech

I've seen it done too mellor, what I'm saying is I wouldn't do it. Attic trusses - fine- they're designed for purpose - but a normal truss shouldn't be tampered with. It's designed in the first place to suit the loads and the spans of the house, and the configuration of the timbers is laid out acordingly.Fixed purlins will only work where there is adequate support underneath them, and in most cases, the bottom boom of a timber truss will be way undersized to take props ..... I just think cutting the roof removes a lot of doubts, and gives a lot more flexibility in the future.

FOXFISH1

if you're planning to have a large family in the future then i would suggest the cut roof.

mine is a trussed roof, which i hope to convert soon, i need to insert steel beams to support the new floor joists and new rafters etc

archtech

If you are putting in a cut roof with the view to possibly converting it later, now is the time to adequately size the ceiling joists (should be floor sized joists). If you put in standard sized ceiling joists now, they will not be adequate to carry a floor at a later date and you will need to put in new joists at that stage.

THE DON FANUCCI

archtech wrote: »

If you are putting in a cut roof with the view to possibly converting it later, now is the time to adequately size the ceiling joists (should be floor sized joists). If you put in standard sized ceiling joists now, they will not be adequate to carry a floor at a later date and you will need to put in new joists at that stage.

should I use 9x2 inch timbers for the attic floor for conversion later on? is that sufficient

BryanF

THE DON FANUCCI wrote: »

should I use 9x2 inch timbers for the attic floor for conversion later on? is that sufficient

We can't offer structural advice, your eng will advise you

hoodrats

THE DON FANUCCI wrote: »

should I use 9x2 inch timbers for the attic floor for conversion later on? is that sufficient

id say youd be fairly well covered there

THE DON FANUCCI

hoodrats wrote: »

id say youd be fairly well covered there

If I want to covert my attic afterwards. how do I put down flooring if my floor joist is 225mm but I will have 300mm insulation. how do I lay a floor on this? do I add a 3 inch batten on top of my 9inch joist to make it 300mm, and then floor over the whole lot

Gumbo

THE DON FANUCCI wrote: »

If I want to covert my attic afterwards. how do I put down flooring if my floor joist is 225mm but I will have 300mm insulation. how do I lay a floor on this? do I add a 3 inch batten on top of my 9inch joist to make it 300mm, and then floor over the whole lot

What is your engineer or BER guy saying?
It's not just a case of agh sure stick in 225x44 joists. What span is it? C16, C24 timber etc. A floor is a structural item and as such covered under Technical Guidance Document Part A. It needs to be designed by a competent person, not the Internet.

THE DON FANUCCI

3 inch batten on top of the 9inch joist, over 12inchs of wool would do the trick. grand big usable attic then.

Gumbo

THE DON FANUCCI wrote: »

If I want to covert my attic afterwards. how do I put down flooring if my floor joist is 225mm but I will have 300mm insulation. how do I lay a floor on this? do I add a 3 inch batten on top of my 9inch joist to make it 300mm, and then floor over the whole lot

THE DON FANUCCI wrote: »

3 inch batten on top of the 9inch joist, over 12inchs of wool would do the trick. grand big usable attic then.

Are you asking and answering your own questions?