Loft Conversion floor construction methods?

[Lecky78]

Hi everyone, any advice would be great,

Planning to convert my loft into an additional bedroom ( second floor ), live in mid '60s end terraced house. I have had an architect make up some drawings for the proposed conversion, and next step to get a SE before submitting plans to building control.

The loft is a rafter and purlin type and ideal to convert, the first floor has no solid supporting walls below, ceiling joists are (5" X 2") at 400mm centers with span 6960mm wall plate to wall plate, 2650mm headroom. The architect has suggested an off center steel ( to accommodate new stair ) to support new floor, with 225 x 45 joists going to wall plates and 2 steel purlins to support roof rafters. Have been doing a bit of research into alternative methods.

I looked into Tele beam method, looked good/ideal but very expensive on overall build. I was wondering if anyone has used I-joists to span wall plate to wall plate on similar build? ( Strong Tie ) or if even possible.I'm not trying to cut corners and going to get a SE survey next. I will have to get work done on roof to fit vents / windows, and removing roof tiles to fit I-joists would be great and cost effective, as steels will involve party wall agreement and cranes etc.

Any advice / experience would be great and appreciated. Working on a budget and doing a lot of work myself, regards Paul. Have PDF drawings on file

 

[noseall]

The loft is a trussed rafter type and ideal to convert

Roof trusses - ideal to convert?

Who told you this?

...or do you mean summat else?

 

[Lecky78]

Ye sorry about that, my error. Should have been rafter and purlin type loft.

 

[pinenot]

They actually make timber engineered attic joists, so in answer to your question the answer is technically yes.
The obstacle you will have is whether there's enough room to fit them on the wall plate and the inside pitch of the roof (cutting an angle on the end is not an option) You could build a suspended floor though, using timber I beams! depending on how much headroom is available?...pinenot

 

[^woody^]

Upload an image of the existing loft joist layout (including stair location) and section through the loft showing the height from joist to ridge

 

[Lecky78]

Hi Woody, have been trying to upload image but wont let me up load PDF file. I will print the images and scan them tomorrow then upload pics!

 

[RonnyRaygun]

Hi Woody, have been trying to upload image but wont let me up load PDF file. I will print the images and scan them tomorrow then upload pics!

Try zamzar.com It will convert practically any picture file type to practically anything else.

Anyway, it's not really practical to span nearly 7m using timber of any description as it will need to be very deep, costing you a lot of valuable headroom.
I guess it depends on how much headroom you can afford to lose, or you can live with in your loft conversion. Don't forget you will also lose height at ceiling level due to insulation and possibly ridge beam.
And you will still have to trim the stair opening somehow.

 

[pinenot]

copy your pdf pics to paint, save as a .jpg upload to your image folder on this site (below post reply box - 'Upload New Images') choose this image from 'Show My Images' and it will appear in your post - seemples - cheers...pinenot

 

[Lecky78]

Loft Plan

• Lecky78
• 7 Apr 2013
• 1

Existing and proposed

 

[Lecky78]

Untitled

• Lecky78
• 7 Apr 2013
• 1

 

[Lecky78]

Untitled

• Lecky78
• 7 Apr 2013
• 1

 

[freddiemercurystwin]

Typically you would do a steel down each side about 1200 in from the outer wall and then build a structural timber stud wall off of these to support the rafters, which may need to be beefed up. No need for those daft steels he's got half way up the pitch which are going to eradicate any sensibly positioned rooflights and bang your head on/eat into valuable headroom. Then the span between the steels can be accommodated without absurd timbers. The steels can be segmented into 3 of 4 portions and then bolted together in he loft, no need for cranes just some muscle for a day. Technically anything you do to your party wall calls for the Part Wall Act so whether you fit steels or not is immaterial.

 

[Lecky78]

Thanks never new the steels could be in segments. This was just an initial method on plan, the structural engineer ( when I get one ) will get any amendments done with whatever they suggest. Was just looking into all different methods of doing this.

 

[RonnyRaygun]

FMT is right. There's a chance you could trim the stairs with timber once the steels are in place under the dormer walls at floor level. Double or triple joists sometimes work depending on span and depth.

Alternatively the stairs could be trimmed in steel and the dormer wall on one side supported on shorter, stronger joists.

It's not difficult to do and no SE will have you sticking steels where the architect has shown them.

 

[^woody^]

Sack your architect, and engage someone who knows how to design