Loft conversion in a timber framed house

[Jon6838]

Hi everyone, I am considering converting my loft. It is a new build timber kit with a trussed roof. It is approx 6m gable to gable and 7.5 front to back. It's detached with plenty of room either side for sliding in steels.
Every trussed roof I see getting converted has an internal block wall to rest the steels on. As my internal walls are timber frame, what would the steels rest on? I hear varying opinions on steels on timber. Any advice would be appreciated, many thanks, jon

 

[bernardgreen]

Timber frame construction ( posts and beams bolted together ) or timber panel construction ( panels made from thin timbers and plywood sheets which are nailed together ).

With panel construction you will be limited by how much extra weight the wall panels ( on the upper floor ) can carry. The horizontal timber at the top of the panel may be only 50mm by 75mm. That is able to take the distributed weight of the ceiling but very unlikely to be able to take the point load of a steel supporting a floor in the loft.

With a frame construction the size of the top beam will determine how the load of the loft floor can be carried.

 

[freddiemercurystwin]

Is it SIP's or traditional timber frame?

 

[Jon6838]

It's traditional timber frame/panels. To be more specific, 90*40 c16 timbers sheeted with osb. I've no doubt that these can't support the load on their own, but was just wondering what my options were? Maybe cripple studs under the load points? I'm just not sure as to what the 'done' thing is my style of house

 

[bobsuerita]

depending on the pitch of the roof
dormer conversion or just velux
if its a new build speak to the company who made the frames as they are the same frame for standard truss to attic truss
they will then tell you if posible you might have to open up walls on ground and first floor to add extra studs in loading areas but like i say speak to the timber frame company first

 

[Jon6838]

I wouldn't even contemplate resting a steel on them as is, I am just trying to get an idea of the different methods (if any) of converting this kind of roof as timber kits are the most common build these days and every loft conversion company seems to convert them no problem, yet all the videos and pics available all have block walls for the beams. I don't mind opening up walls to put in more studs if that's the only way to do it but that's eight areas of the house to open the walls, 2 of which has a staircase and kitchen in front of them!!
Even if this was the way forward and I added all the extra studs, the beam would still only be resting on the 90mm wide timber in the loft, I thought the minimum was 100mm?

 

[bernardgreen]

if its a new build speak to the company who made the frames

That is the best way forward

Retro fitting cripple studs would be very difficult as cutting the OSB would compromise the integrity and diagonal bracing of the panel

 

[Jon6838]

Why would I have to cut the osb? Would I not just be adding studs of the same size/width?

 

[bernardgreen]

As I understand ot "cripple studs" are fitted as part of the design when the panels are manufacturered and are between the sheets of OSB. They are fitted under window cills to reduce any warpling of the timber of the cill and at other similar weak points around holes cut in the OSB sheets

A load bearing post from ground to loft would not be a cripple stud

 

[Jon6838]

The osb is only on one side of the timber kit, the cavity side. When the internal plasterboard is removed you are looking at the studs with the osb on the back side. Adding studs here is adding studs within the timber kit panel, why would this not be a cripple stud?

 

[Jon6838]

I do mean add load bearing studs under where the steels would be, my terminology may be wrong here!!! I thought that was a 'cripple' stud, to stop it 'crippling'? Every days a school day!

 

[Jon6838]

King studs!?

 

[bernardgreen]

The osb is only on one side of the timber kit, the cavity side

Suggests they are not standard construction panels.

https://sipsecopanels.co.uk/sips/what-are-sips/
Structural Insulated Panels (SIPs) are a structural frame made from a sandwich of two layers of structure and one layer of insulation. The standard 144mm Sips Eco Panel comprises of two layers of Oriented Strand Board (OSB), either side of 122mm of premium carbon treated expanded polystyrene (EPS).

 

[Jon6838]

Definitely not sips. Standard timber frame construction

 

[freddiemercurystwin]

Suggests they are not standard construction panels.

https://sipsecopanels.co.uk/sips/what-are-sips/
Structural Insulated Panels (SIPs) are a structural frame made from a sandwich of two layers of structure and one layer of insulation. The standard 144mm Sips Eco Panel comprises of two layers of Oriented Strand Board (OSB), either side of 122mm of premium carbon treated expanded polystyrene (EPS).

Do pay attention bernardgreen, that was established at post No. 3. Anyway, if traditional timber frame then it will have been built by chippies off some site specific drawings, not from a 'timber frame company' so unless you happen to have the Building Regs drawings that show the size of the timbers etc etc you'll need to appoint a good designer and structural engineer who will need to determine the eligibility of the existing frame to take the new loft. Some exposing of existing structures may be in order and there may be the need to introduce some additional structure at ground or first floor level to, it’s all doable but it’ll be more costly and complicated than a traditional masonry constructed house. Check you don’t need planning permission too, many new homes have their permitted development rights restricted.