An Engineering Challenge

[Mee]

This is merely for fun and for people to make suggestions, there is no right answer and obviously no wrong answer, so what would you do and how would you approach, and resolve this minor problem?

This is a live project which is currently part way through.

This is an industrial building which is two storeys high, with a pitched roof and loft to give it three storeys, and we have to make a roof for it and erect it.
The walls are cut stone and 6' thick and are structurally sound, but we cannot place roof trusses directly onto the stone as the weight would cause a "blow out" which is the weight of the roof forcing the top stones out and the roof collapsing, and we cannot use tie bars as the roof space has to remain open.

How would you approach it and what is your solution?

 

[Agrismith]

Where abouts is the loft floor in relation to the top of the walls is it close enough that the tie rods could be run just under the floor ?? Or is it several feet difference
If several feet difference use structual i beams for the roof to the same design as a single span barn with feet on them so no to push down squarely on the wall and the i beam taking the strain to stop the wall bowing

 

[Dee J]

Either cast a re-inforced concrete ring beam around the top of the walls or fabricate a perimeter in steel to tie the top of the walls together and resist the spreading action of the roof.

 

[MrFluffy]

Sit the roof supporting structure on pillars so that the load path reaches down to the slab. That's exactly the situation we did here with my barn conversion.
The wall on the workshop to be barn is buckling/bellying because of truss load bearing down on the drystone wall over the years, and I'll add a pillar to support each end of the truss to stop it walking further over time when I do the floor slab groundworks.

 

[Swift&Bold]

Mansard truss and concrete ring beam or support it on pillars

 

[Rudi McAnichal]

I have seen lots of farm steadings where original stone walls were left in place, and a new roof supported on a portal frame (sometimes inside and sometimes outside the old walls).

The walls are cut stone and 6' thick...

Am I reading the stone wall thickness correctly? Six FEET thick sounds like more like a mediaeval castle than an industrial building, whereas six INCHES would be very thin for a two- or three-storey building.

 

[angellonewolf]

my first thought was to drop steels to the ground floor to support a new roof frame prob not the easy route

steel all around the edges and plates on the out side to tie it in but this would add weight the walls

 

[slimjim]

well you need to tie the roof somehow,

So that would suggest at floor level, with it tied at ceiling level.

 

[8ob]

Piece of cake, have the structural steels rolled to form a semi circle and bolt them straight down on the wall. Then have the roofing sheets rolled, same as a Nissen hut.

Where's` my cigar?

Bob

 

[Rocketman]

Get a structural engineer to do the calcs and take it from there. Totally irrelevant suggesting solutions without that info. Just because it's a pitched roof it doesn't mean you will get blow out on the side walls - it rather depends on the design of the roof structure and loads involved.

 

[brightspark]

for a start all the measurements of building need to be known before anyone can make a suggestion otherwise your just guessing a structural engineer needed

 

[The_Yellow_Ardvark]

Where's` my cigar?

In the shop.

 

[Rig Pig]

Attach a large balloon to the roof and fill it with enough helium to fully support the weight of the roof.

 

[The_Yellow_Ardvark]

If the OP could post pictures and or a drawing, then the experts here will be able to give a straight honest reply.
That way the thread will be short and to the point.
Not becoming a argument.

 

[optima21]

ask an architect, then if it goes wrong you have someone to blame

 

[brightspark]

ask an architect, then if it goes wrong you have someone to blame

structural engineer .architects just design others do the calcs

 

[Rig Pig]

The moderation seems to be a bit ott as the op starts of with 'just for fun' ????

 

[gaz1]

you would have to spread the roof load via ( purlin ) beams placed in desired locations at the apex of the roof to evenly spread the load over the roof and walls

however the beams are of poor quality with wood beams and therefore have to be doubled and pinned using coach bolts, done it often enough with dormer buildings front beam double up and moved if needed and also done it with rear beam as well and thats just for a dormer built structure

the other alternative is to use steel beams from floor to roof height at farthest beam spread load and pin them to each other per floor further building another cross beam



instead of the whole roof weight being put on the walls using the purlins/beams would spread the weight of the roof you would be as low as a quarter of the weight left on the wall plate used

 

[thinfourth]

Money no object?

Then some utterly beautiful laid up glulam beams with the correct curve for the roof

 

[WorkshopChris]

Without knowing the dimensions it all guess work, but i would go with a universal beam around all four sides of building sitting in the centre of the 6 foot wall.
Bolted together then roofing steel work siting on top of UB.