Loft boarding - Truss, Brace, Kings & Queens

[jarvo]

Hi all,

I live in a newish build circa 2013 and have a small loft space that I would like to partially board out for very light storage.
The loft is roughly 3.7m wide by 5m long, with an area roughly 3.6m x 3.6m which could be boarded when the loft access is taken into account.

I'm currently looking at a LoftZone kit (7m2) to raise the boards above the 270/300mm of insulation that's already in place.

So my problem is the roof is a truss design with large vertical posts right down the centre of the loft space with support struts, which makes boarding rather difficult.
Not sure if this is called a King post design as different sources show different names
(its 1.87m from the centre of the posts to the loft edge)

What would be the best way to board it out, start from the centre King post and go 1.2m (maybe 1.8m) out to make the most of the head room.
Ideally i would like to avoid cutting every single loft board to make them fit around the King post as it doesnt have to look beautiful just for storage.

Secondly the diagonal strut braces, could they be repositioned horizontally (red line) to give easier access for storage?
Or would this substantially weaken the roof.

A couple of images below, sorry about the poor quality.. my phone doesnt seem to like the low light levels

thanks all

 

[noseall]

Hi all,

I live in a newish build circa 2013 and have a small loft space that I would like to partially board out for very light storage.
The loft is roughly 3.7m wide by 5m long, with an area roughly 3.6m x 3.6m which could be boarded when the loft access is taken into account.

I'm currently looking at a LoftZone kit (7m2) to raise the boards above the 270/300mm of insulation that's already in place.

So my problem is the roof is a truss design with large vertical posts right down the centre of the loft space with support struts, which makes boarding rather difficult.
Not sure if this is called a King post design as different sources show different names
(its 1.87m from the centre of the posts to the loft edge)

What would be the best way to board it out, start from the centre King post and go 1.2m (maybe 1.8m) out to make the most of the head room.
Ideally i would like to avoid cutting every single loft board to make them fit around the King post as it doesnt have to look beautiful just for storage.

Secondly the diagonal strut braces, could they be repositioned horizontally (red line) to give easier access for storage?
Or would this substantially weaken the roof.

A couple of images below, sorry about the poor quality.. my phone doesnt seem to like the low light levels

thanks all
View attachment 319460View attachment 319456

There is very little that you can remove from a truss roof, as they are a bare bones structure (slender sections) in the first place. You certainly can't re-position the diagonal bracing, no.

 

[jarvo]

Thanks @noseall, I had done some research but couldn't find anything conclusive

 

[^woody^]

You just have to cut or notch the boards around the truss struts as best you can. May need timber supports fixed to the sides or undersides of the struts to support the cut edges.

 

[jarvo]

Thanks @^woody^ I think thats probably the best i can do, i cant see any easy way around it

 

[jarvo]

Out of interest why does the NHBC say Chevrons are needed for spans over 8m.
The roof in question is probably closer to 4m and 2 storey.

7.2.9 Bracing for trussed rafter roofs - NHBC Standards 2019

nhbc-standards.co.uk

 

[^woody^]

All trusses need bracing. Diagonal bracing for shorter widths, chevron (ie double/treble etc diagonal) for wider widths.

 

[brennan2470]

All trusses need bracing. Diagonal bracing for shorter widths, chevron (ie double/treble etc diagonal) for wider widths.

Do you know of any requirement to brace the truss chords if the rafters have chevron bracing? My chords are braced diagonally but I am unsure if I can remove them when I build an independent mezzanine floor which will involve adding 8x2 joists adjacent to (but not connected to) the existing truss cords.

I assume these braces are merely there to spread the load of somebody walking along the truss chords, which I won’t be doing, so can be removed? Cheers

 

[noseall]

Do you know of any requirement to brace the truss chords if the rafters have chevron bracing? My chords are braced diagonally but I am unsure if I can remove them when I build an independent mezzanine floor which will involve adding 8x2 joists adjacent to (but not connected to) the existing truss cords.

I assume these braces are merely there to spread the load of somebody walking along the truss chords, which I won’t be doing, so can be removed? Cheers

Some bracing can be replaced with (12mm?) ply sheathing. It can't be removed altogether. No Idea how you'd get full sheets into the loft though....

We've use sheathing in place of DB on a vaulted roof, whereby the DB would have messed up the internal rake, as the DB has to continue down to the WP (wall plate).

 

[brennan2470]

Thanks. I’m speaking specifically about the truss chords and not the diagonal bracing elsewhere such as the rafters. I think the bracing you’re referring to (which can be replaced with ply) are the rafter DB’s which connect to the wall plate. I can’t see any requirement for DB’s on the truss chords.

7.2.9 Bracing for trussed rafter roofs - NHBC Standards 2024

nhbc-standards.co.uk

 

[brennan2470]

Deleted

 

[noseall]

I am unsure if I can remove them when I build an independent mezzanine floor which will involve adding 8x2 joists adjacent to (but not connected to) the existing truss cords.

Surely this is a whole new (Structural Engineer territory) can of worms?

 

[brennan2470]

Surely this is a whole new (Structural Engineer territory) can of worms?

I’m comfortable with the new structure that’s being erected, but just need to know if I can remove the diagonal braces along the truss chords given they interfere with where the chipboard flooring will go, and from what I can see, there is no requirement for them to be there.

 

[noseall]

I’m comfortable with the new structure that’s being erected, but just need to know if I can remove the diagonal braces along the truss chords given they interfere with where the chipboard flooring will go, and from what I can see, there is no requirement for them to be there.

I'm guessing there will be other bracings etc that will require removal, for the new floor? Do you have an image or a design?

 

[brennan2470]

I won’t need to remove any other of the truss braces as the current truss chords are 3 inch deep and the new joists I’m running parallel to them are 8 inch deep. These new joists will hang 5 inches below the truss chords and therefore finish level with the top of the chords (well technically they can finish wherever I want them to, but without removing the chord bracing I can’t have them any higher). Joist hangers will be nailed to the wallplate that sits atop the masonry walls either end supporting the trusses.

The issue I have is laying the chipboard flooring across the new joists because of the diagonal bracing (4x1”) spanning the chords getting in the way. I can’t find anything that suggests it needs to be there, but I may very well be wrong.