Attic conversion question

dodzy

Looking into maximising space with an upcoming project ( attic conversion ). I've attached a drawing of the internal setup ( trussed roof ). I need to know is there a system which is used to determine the maximum distances for the RSJ placement ? Obviously, the further towards the eaves, the greater the strain on the rafters once the internal cross sections are removed.

Would it be feasible to achieve the layout in the diagram or would the span be too great ? The existing rafters directly under the tiles are 4" x 1.5" . 600mm spacings.

Any help appreciated

dodzy

Anyone care to enlighten me on this please?

Prenderb

I can't open your file, unfortunately, but even if I could, I'd probably end up suggesting that you pay for professional advice - architect or structural engineer - given that it sounds like you want to modify your roof structure.

Disclaimer: Opinion only. Seek professional advice.

Query: RSJ? Really? Sounds very heavy duty. Get professional advice.

PaulieBoy

I can't open your file either!
I've done it before, but had to do the whole design myself as I could not find anyone willing to even have a look at it.
I built a "roof within the roof" if you get me, then your free to place the RSJ's where you like.
If you do that it's pretty straight forward, else it's highly suspect to interfere with the truss roof.

dodzy

Prenderb wrote: »

I can't open your file, unfortunately, but even if I could, I'd probably end up suggesting that you pay for professional advice - architect or structural engineer - given that it sounds like you want to modify your roof structure.

Disclaimer: Opinion only. Seek professional advice.

Query: RSJ? Really? Sounds very heavy duty. Get professional advice.

1. External structure will not be changed. Only internal support trusses.

2. And yes, they ( RSJs ) are heavy but will come in 4 sections to ease fitting and transport. Predrilled & plated for bolting at centers. Will pay for pro advise if need be but i'm sure I can go without for the moment.

Paulieboy wrote: »

I built a "roof within the roof" if you get me, then your free to place the RSJ's where you like.
If you do that it's pretty straight forward, else it's highly suspect to interfere with the truss roof.

The trusses will have to go, as is the norm with these type of conversions. Have a look at the attachment and let me know your thoughts

Martron

i think the colour were mixed up but i think you will need a purlin construction .

nothing is impossible but i think you will also have to upgrade what will be you floor joists as the prefabbed trusses generally are not strong enough to support regular traffic.

PaulieBoy

Prenderb wrote: »

Query: RSJ? Really? Sounds very heavy duty.

It's perfectly normal to use an RSJ in an attic conversion.
In some cases it's can be done without, but normal to use one.

dodzy

Martron wrote: »

i think the colour were mixed up but i think you will need a purlin construction .

nothing is impossible but i think you will also have to upgrade what will be you floor joists as the prefabbed trusses generally are not strong enough to support regular traffic.

I am aware that the existing truss horizontal sections are not designed to support flooring / furniture / people etc; the RSJs will support new joists which will then support the new flooring ( either mounted inside the [ section of the RSJ or by using joist hangers.

The question still stands..... if any body can assist.

endasmail

get in a carpenter who knows what he s at ,and he ll tell fairly quickly

dodzy

Anybody recommend a RSJ supplier in the Dublin area ? Just doing some comparisons on costs.

sterlo

Frank Kane Steelworks in Swords - 01 8401925