Does a knee-wall always need to touch the end truss

[tractor-pete]

I have a modern (5 year old) house with trussed roof and want to convert the loft with steels, etc.

I'm trying to get a rough idea where the knee-walls would be on either side, to get a feel with the eventual room width and window positions, etc.


Do the new knee-walls sitting on the new steels normally touch the roof rafters, where the final truss meets (red arrow below)? Or can the wall be pushed further out (red dotted box) ...increasing the total room width and lowering the minimum height of any velux windows we install?

The end of the truss currently sits around 1.5m above the existing loft floor, which feels quite high and I worry the velux windows will be very high up and you won't really be able to see out of them unless you stand up.

Thanks

 

[jks7492]

No the wall doesn't necessarily need to be at the same position as the original truss joint - whoever is designing the loft conversion should make an assessment of the rafter sizes and determine the required strengthening based on the position of the stud wall.

As you push the wall further outwards you'll get to a point where you don't really get any benefit of doing so - the floor span becomes larger so possibly increases your joist depth, the ceiling level reduces to the point where you potentially end up with unusable space within the eaves, and the access for installing the steels gets more difficult.

 

[^woody^]

The position of a strut on a truss is nothing to do with where a rafter needs supporting.

Normally the eaves wall would be positioned to allow for MOE cill heights, or where any dormer cills would be (900-1050mm high) or in a similar place if only fitting roof windows higher up, as the space beyond this is not really useable and is wasted.