Cutting ceiling joist in trussed roof.

MassiveJim · 21 Jun 2022 at 12:21

I am wanting to extend our loft hatch opening and fit a loft ladder, but where it is currently would require cutting a single joist.
The roof is trussed design and every single rafter/joist is trussed, the joists are 3 x 2.

I can't find a clear answer online, do I need an engineers structural calc for this, or can I just brace the remaining joists and add double trimmers between them to fit the bigger hatch ?

Deleted member 77746 · 21 Jun 2022 at 12:23

for god sake don't just go ahead and cut stuff without it been checked first. Potential of a whole ceiling / roof coming down.

200sols · 21 Jun 2022 at 12:50

How to Enlarge a Loft Hatch

How to enlarge a loft hatch, fit a DIY ceiling hatch, install a loft hatch and learn how to strengthen timbers to make a loft hatch bigger

www.diydoctor.org.uk

MassiveJim · 21 Jun 2022 at 15:18

Bouton Aide said:
for god sake don't just go ahead and cut stuff without it been checked first. Potential of a whole ceiling / roof coming down.

the entire point of this thread.....

MassiveJim · 21 Jun 2022 at 15:22

200sols said:
How to Enlarge a Loft Hatch

How to enlarge a loft hatch, fit a DIY ceiling hatch, install a loft hatch and learn how to strengthen timbers to make a loft hatch bigger

www.diydoctor.org.uk

That is pretty much the standard way of doing it (properly) but I need advice specific to a trussed roof.

I have read on one site for example that you shouldn't cut any joists that have trusses attached to them.
But that is only one source, can't seem to see anything else that specific.
Some trussed roofs have trusses on every other joist but mine is not like this.

Was hoping someone on here had some experience with this.

dl8860 · 21 Jun 2022 at 16:44

Can you share a picture, or sketch a layout?

I'm a structural engineer, though very much don't specialise in Timber or Residential.

Buffman · 21 Jun 2022 at 19:08

200sols said:
How to Enlarge a Loft Hatch

How to enlarge a loft hatch, fit a DIY ceiling hatch, install a loft hatch and learn how to strengthen timbers to make a loft hatch bigger

www.diydoctor.org.uk

Aye thats how I did mine. Pretty much doubled the length of the opening

Pictures

(this was before plastering and decorating)

Now (not quite fully decorated)

You need to post some pics OP

sdavlaws · 22 Jun 2022 at 12:45

If you look at the trusses one of the nail plates should have a label pressed in with it normally one of the webs half way up the rafters. It should tell you which company made them if you contact them they should be able to arrange for the detail to be produced for a fee if they still have the production records.

vail3r · 22 Jun 2022 at 12:57

Can you not enlarge it running parallel to the trusses? most standard loft hatches are made to fit into standard spacings

MassiveJim · 22 Jun 2022 at 22:45

vail3r said:
Can you not enlarge it running parallel to the trusses? most standard loft hatches are made to fit into standard spacings

I would have to move the hatch to do that . Which is still an option, but I prefer to leave it where it is if I can.

I will get some pictures up eventually (just busy with various other jobs at the minute) but not sure what use they will be.