Noggins for engineered truss

[JohnLaura]

Hi, I’ve got a single storey garage workshop with an engineered truss roof.
I want to fit solar panel rail brackets, secure them into a noggin/OSB board.
Could anyone recommend how to fix as the trusses can’t be drilled, notched or cut.
Welcome any input.

 

[addjunkie]

When you build a roof using bought trusses, you lay various boards inside and nail them on using a nail gun. On the drawings its fairly vague, leaving you open to use “good building practice”.
If it were me Id cut and fit noggins and just fix to the truss with a nail gun. Look around any modern housing estate how many have loft boarding screwed to roof trusses to store the family junk!

I have attached truss drawing I used on a barn conversion for you to read the vague text.

 

[JohnLaura]

Thanks addjunkie. I see your trusses are 600 centres, mine are 450.
What size type nail would you use, can I ask.
My worry is anything I do, if wrong, will affect the integrity, giving me a headache down the line.
Can I ask you whether the following also sounds acceptable - to make a small box to sit in between rafters, rising above tiles, glued and nailed in between rafters and using a sicaflex or similar adhesive to glue a toughened glass pane to act as a roof light, giving me some natural light to work by.

 

[gaz1]

if you want to add solar panels and cant drill the trusses you can strengthen them and drill into the new support beams

these can be put at side of the engineered trusses screwed and supported where needed

 

[frank horton]

I use these a lot...double sided spiked washer when joining an extra board along side a roof truss (to stiffen up said truss)

they dig in very well....
if u cant use bolts I use heavy G clamps to make em dig in then wood screws where necc....

 

[Pigeon_Droppings2]

Usually the safest place to screw/bolt is a long the centre line of the thickest face as that's usually where the stress on the beam is close to zero.

As suggested above its probably safer to sister a beam along the existing truss and then use that.

 

[JohnLaura]

if you want to add solar panels and cant drill the trusses you can strengthen them and drill into the new support beams

these can be put at side of the engineered trusses screwed and supported where needed

Thanks gaz1 how long would you suggest the sister support be, 600mm long glued and screwed to the truss, something like that?
I just want to make sure I get it right.

 

[JohnLaura]

I use these a lot...double sided spiked washer when joining an extra board along side a roof truss (to stiffen up said truss)View attachment 518164
they dig in very well....
if u cant use bolts I use heavy G clamps to make em dig in then wood screws where necc....

Hi Frank, that sounds good. How long would you suggest the support be?

 

[gaz1]

you have to build secondary roof trusses with longer depths to be used as they wont match the prebuilt models

there easy enough to build but a frame truss is still the same

 

[addjunkie]

Thanks addjunkie. I see your trusses are 600 centres, mine are 450.
What size type nail would you use, can I ask.
My worry is anything I do, if wrong, will affect the integrity, giving me a headache down the line.
Can I ask you whether the following also sounds acceptable - to make a small box to sit in between rafters, rising above tiles, glued and nailed in between rafters and using a sicaflex or similar adhesive to glue a toughened glass pane to act as a roof light, giving me some natural light to work by.

I used 90mm ring nails using a plaslode nail gun.

I think you are over thinking this, for light fit a velux window or equivalent. Lots of properties with manufactured trusses have solar panels on the roof. I suspect @roofman has fitted rails etc in the past. If your really worried remove the tiles and use integrated panels, they are not that much more.

 

[gaz1]

Thanks gaz1 how long would you suggest the sister support be, 600mm long glued and screwed to the truss, something like that?
I just want to make sure I get it right.

it depends on your roof size and lengths that is needed

 

[Agroshield]

...the trusses can’t be drilled, notched or cut.

Driving one or more nails or screws into the truss does not appear to fall within those limitations. How are the battens that carry the tiles fixed to the trusses?

The prohibited methods all involve reducing the cross-sectional area of the structural member in one way or another.

Gluing a secondary piece of material onto the side of the truss with standard PVA wood glue would also work, providing it is clamped well while the glue sets.

 

[JohnLaura]

I used 90mm ring nails using a plaslode nail gun.

I think you are over thinking this, for light fit a velux window or equivalent. Lots of properties with manufactured trusses have solar panels on the roof. I suspect @roofman has fitted rails etc in the past. If your really worried remove the tiles and use integrated panels, they are not that much more.

Agree,,,overthinking as usual.450mm rafter centres seems to small for a velux,so thinking of making up a shoe box upstanding ,lead or rubber flashing and thick plexi as its an un heated garage/workshop

 

[JohnLaura]

Driving one or more nails or screws into the truss does not appear to fall within those limitations. How are the battens that carry the tiles fixed to the trusses?

The prohibited methods all involve reducing the cross-sectional area of the structural member in one way or another.

Gluing a secondary piece of material onto the side of the truss with standard PVA wood glue would also work, providing it is clamped well while the glue sets.

I like the Glueing cut osb to either side of the rafter,pilot drill and screw a few screws to keep it clamped ,thanks

 

[Nomad]

Agree,,,overthinking as usual.450mm rafter centres seems to small for a velux,so thinking of making up a shoe box upstanding ,lead or rubber flashing and thick plexi as its an un heated garage/workshop

Agreed. I've bought 3 Velux windows in the last 3 years, minimum width they do is 55cm

A complete VELUX size chart for replacing your roof windows!

VELUX windows come in all different sizes. View our VELUX size chart to find your perfect pitched or flat roof window.

www.yarddirect.com

There are alternatives to velux, maybe ask if other makers sell narrower windows?
Beware - you will have very little space for glass after you fit the frame between 45cm rails.
https://www.mig-welding.co.uk/forum/threads/velux-windows-any-alternative-makes-to-consider.140719/

Another option is to cut a piece out of 1 joist* to fit a window, then fit cross-braces between the joists either side as my builder did :

Post in thread 'Stuff you have fixed today'

Aug 20, 2025

Did the last few jobs on the recently replaced roof today - I finally have hot water again

* Builders fitted a new roof & window 2 years ago, it leaked every winter so they recently stripped the tiles ( they left me to remove & refit the water heater, they had not installed it so removing it to fix their leaking tiles wasn't their job)
A mate helped me to lift the tank & panel off the roof, and refit it after the builders had replaced the tiles & insulation & fitted a waterproof membrane (original subcontractor hadn't fitted a membrane...)


When the tiles were...

• Nomad

• 

* no sure if joist is the right term but you get the idea

 

[JohnLaura]

Thats some journey but im glad your getting it fixed right.Cutting my rafter isnt an option as its an engineered fink truss,they shouldn’t be cut or altered.thanks again for the help

 

[addjunkie]

Thats some journey but im glad your getting it fixed right.Cutting my rafter isnt an option as its an engineered fink truss,they shouldn’t be cut or altered.thanks again for the help

They are often cut when loft conversions are done, but extra is added to make up for it! But it needs a bit of proper input rather than just sticking a few bits in.

 

[JohnLaura]

They are often cut when loft conversions are done, but extra is added to make up for it! But it needs a bit of proper input rather than just sticking a few bits i

I worded that wrong i should have said,my limited skill set means no truss cutting,sistering and bracing etc..
Thanks for your reply and the other good folk here,

 

[addjunkie]

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This might fit between your trusses. Worth a phone call to check!