Can we use an i joist instead of ecojoists on an 8.1 span?

[CalvinHobbes]

Trying to save £. We are getting told if we change to roof trusses we won't have to use ecoojoists and make a big saving. Would it be possible to use an i joist (even with a steel) instead and leave roof as planned?

[MikeSharp01]

Are you saying you would loose the vaulted ceilings if you go for Trusses. 

[Dave Jones]

maybe, its attic trusses you want.

[saveasteading]

8.1m is a very long clear span. Ecojoists or similar by another name will just do it but will be deep and expensive.

 

Trusses rely on filling the space with lighter weight diagonals,  but they fill the space and you lose the rooms.

 

What your drawing shows looks optimum to me. Expensive but optimum.i

[Mr Punter]

I don't think there is much difference in cost between a metal web engineered joist and an OSB web engineered joist.

 

If you have trusses and no ridge beam you would need a chord lower down and would not get the vaulted look.

 

The zinc is probably expensive.

[saveasteading]

From memory the osb web versions give more options for non standard joists like yours, so are a bit cheaper.

Metal for standard spans.

But with fluctuating  osb prices it needs checking.

 

An off the wall suggestion, esp if you have an SE, is to consider plating the ceiling in plywood, which might allow reductions in joist constituents, and be less deep.

[Temp]

Perhaps I'm missing something but I don't see the connection between the use of a structural ridge beam to support the roof and the type of floor joist. 

 

Are there posts under the ridge beam that bear on the joists? Normally the beam would be supported on the gable end walls, interior walls or posts that go all the way down to the ground floor.

 

[ETC]

@CalvinHobbes

Trying to save £. We are getting told if we change to roof trusses we won't have to use ecoojoists.

Not necessarily. If you change to attic trusses them yes - the bottom chord becomes the floor joist. If however you change to a standard fink truss with a raised collar then no you will still need to keep the EcoJoists.

 

and make a big saving. Would it be possible to use an i joist (even with a steel) instead and leave roof asplanned? Yes. Place a steel beam centrally in the room to break the span of the IJoist or whatever you’re planning to use. Probably the cheapest option but factor in cost of steel (including fire protection) SE fees and SE to look at supporting walls and structure to make sure the steel beam can be supported. The roof can stay as it is.

[ETC]

Looks like a nice house from the section - would love to see the rest of the drawings. Not sure how the gutters will work though.

[CalvinHobbes]

3 hours ago, MikeSharp01 said:

Are you saying you would loose the vaulted ceilings if you go for Trusses. 

I think we would still have it but could see the roof trusses. I got the impression they would carry part of the load from the floor.

 

[saveasteading]

My feeling is that the extra steel beam and supports woyld exceed the saving on joists, and complicate construction . This based on a project I did using fabricated joists to clients surprise. Not a lot in it, and it would need calculating both ways......but then your SE rightly  has another fee.

 

Whoever told you that trusses might be better, get them to sketch it so it us clear what they meant. In doing so they will likely change their mind anyway. If not, we may see a great idea.

 

[saveasteading]

Personal or practical...?.   I would never have an internal gutter. If they block, the water runs down the wall , at best.

When not blocked, the rain runs down pipes somewhere inside your building. Making a noise, breaking the insulation layer, and someday blocking or leaking. And for what?

 

External gutters and pipes will also save you £50/m at a guess. There are attractive ones.

[CalvinHobbes]

2 minutes ago, saveasteading said:

Personal or practical...?.   I would never have an internal gutter. If they block, the water runs down the wall , at best.

When not blocked, the rain runs down pipes somewhere inside your building. Making a noise, breaking the insulation layer, and someday blocking or leaking. And for what?

 

External gutters and pipes will also save you £50/m at a guess. There are attractive ones.

Yep it's why we are now doing external

[CalvinHobbes]

9 minutes ago, saveasteading said:

My feeling is that the extra steel beam and supports woyld exceed the saving on joists, and complicate construction . This based on a project I did using fabricated joists to clients surprise. Not a lot in it, and it would need calculating both ways......but then your SE rightly  has another fee.

 

Whoever told you that trusses might be better, get them to sketch it so it us clear what they meant. In doing so they will likely change their mind anyway. If not, we may see a great idea.

 

Thinking now if the walls underneath are supporting perhaps we could rest ecojoists on them and get 2  instead of one for each width?There is still a section that definitely has no walls which is 6.5m long so maybe a steel beam there?

 

[saveasteading]

The walls have to be structural, and may be thicker than the norm to support the long span.

Then there is no point on doubling up the joists...the SE and supplier will advise the spec. 

NB..  if the optimum centres don't suit plasterboard sizes, it would be best to ignore that, buy the best value joists, (for example 350 cc) and counterbatten for the ceiling.

[JohnMo]

41 minutes ago, saveasteading said:

External gutters and pipes will also save you £50/m at a guess. There are attractive ones.

Have to agree, once the gutters have been there a month no one ever looks at the again, except for cleaning them once or twice a year.

 

Lots of fiddly details that have to be correct, none of cheap.  If you ever have a leaking gutter, a normal one drips on your head, eventually you'll fix it, no harm done, integrated, could leak for years and make a good old mess of the house structure.

 

I would get them to itemise the cost saving, maybe not much savings overall to change the joists, maybe more saving from getting a second supplier to quote. We have 9.5m long posi rafters in the gand scheme not expensive, come ready to drop in place. The extra I paid for the rafter, I saved twice over on labour for the architect solution.

[CalvinHobbes]

Somehow I found a missing quote on my email for the posi joists and posi rafters from Haldane Fisher for  £3827 which is a lot less than the others (some double).

Edited June 3, 2023 by CalvinHobbes

[saveasteading]

2 minutes ago, CalvinHobbes said:

some double)

Half / double  doesn't seem right. Best check their input?

[CalvinHobbes]

Yep have handed it over to architect and excellent joiner to check. The way they have designed their quotes differ because of the design and systems. The cheapest was posi joists, the most expensive was space joists.

Also in this whole journey so far wild differences in prices for the same things has been happening. It doesn't surprise me because at the supermarkets the same thing is happening.

Edited June 3, 2023 by CalvinHobbes

[Iceverge]

Can you post a full screen shot of the drawing ( without personal details)

 

I'm unsure as to the total design and where you intend to make savings? 

 

At the moment your rafters are pressing down on the wall and Steel I Beam at the apex  (BLUE) They are pressing up ( RED) and in turn transferring the load to the foundations via the walls. I assume the I beam is supported by pillars or the gable walls.  It's pretty normal and allows your chippies to use off the shelf timbers and I can't see it as a very expensive solution. 

 

The Ecojoists ( metal space joists- pozi joists) for the floor of the upstairs won't really have much effect of the roof AFAIK. 

 

 

 

Attic trusses won't work unless you are prepared to loose some internal space from the rooms for bracing as well as at the apex. 

 

 

An elegant solution might be a scissors (vaulted) type truss. You'll still get a vaulted ceiling but your internal pitch won't be the same as the external. You can do away with the ridge beam then. 

 

 

 

Excuse the ropy drawings.  Here's one from the internet. 

 

 

 

 

 

[CalvinHobbes]

Thanks all, ok with the price of the posi joists now and steels arriving wednesday so will continue as planned.