extending Loft hatch project - need help asap

[wozzaface]

Hi guys, im extending my loft hatch in a 1930s home, at the minute the hatch is between the ceiling joist.Its a semi detached house, the ceiling joists are 3x2 and run from front to back of house, with neighbour on the right. From my inspection none of the roof is supported on the joist i want to remove. Iv bought a abru loft ladder kit the dimensions are 113cm by 55cm.

Iv attached a drawing of my layout and plan.

Untitled

• wozzaface
• 15 Dec 2012
• 2

In drawing 1 this is how it looks now, "C" joist is sat on an interior wall the whole length.

In drawing 2, im going to support all "abc" Joist by screwing a length of 3x2 to "a b an c" (D). Cut out part of joist B and screw in 2 pieces of 3x2 (E) to A B and C. The span between joist A and C is 77cm (the width of my hatch is 55cm).

In drawing 3, im going to screw a length of 3x2 (F) from (E to E). Which will gibe me my required hole to fit my 113cm by 55cm loft kit.

What do you think ?

 

[big-all]

how far from a wall is the bottom off the joists in picture 3??
you need to double up the joists each side if its greater than around 2m wall to wall [span]

 

[wozzaface]

In picture 3, the bottom of my loft hatch (e) would be 50mm away from sitting on my bathroom wall . Which would rund at 90degrees to the joists. You say double up my joists, which ones exactly ?

 

[big-all]

i see the wall at the top off the picture is there a similar wall at the bottom off the picture ??
the ones you double up on is the ones on the left and rhs off the picture as you are transferring load to them from the cut out joist
but as i said dependant on span

 

[Dave-K]

Since you are cutting a ceiling joist it is always wise to double up the joists to each side of the cut section (you are removing "b" so add extra timbers to "a" and "c").
This compensates for the removed strength. Common practice for this type of thing and velux roof lights etc.