Remove decorative ceiling joists for vaulted ceiling

[tvrulesme]

I am in the process of renovating an 18th Century building. Planning to have a vaulted ceiling but to leave the original ceiling joists in place. Below the joists there are what look to be "decorative" joists in place. Would removing these likely cause a structural issue? They were not originally a part of the building fabric.

 

Picture showing joists which I plan to remove or repair/replace

 

Decorative joists before plaster removal

 

Loft space before plaster removal

 

 

 

 

 

[markc]

If they “are” decorative then removing them will not change anything.

are they connected to the walls or simply screwed or nailed to the timbers above?

assuming they are not connected to the walls then removing is no problem and taking them out along with the ceiling will remove load from the trusses above so all ok.

[tvrulesme]

1 hour ago, markc said:

If they “are” decorative then removing them will not change anything.

are they connected to the walls or simply screwed or nailed to the timbers above?

assuming they are not connected to the walls then removing is no problem and taking them out along with the ceiling will remove load from the trusses above so all ok.

 

Many thanks Mark. They are joined to the walls in the sense that it looks like someone has hacked out a bit of brick for them to sit on if that makes sense? Doesn't look very structural to my eyes though....

 

[ProDave]

That is only a ridge board at the top, so you WILL need to retain the "ceiling" height beams that span wall to wall. They stop the roof sagging and pushing the walls outwards.

 

A structural engineer might be able to come up with a scheme where some are removed and some remain, but you would not want to try anything like that without professional input.

[tvrulesme]

2 minutes ago, ProDave said:

That is only a ridge board at the top, so you WILL need to retain the "ceiling" height beams that span wall to wall. They stop the roof sagging and pushing the walls outwards.

 

A structural engineer might be able to come up with a scheme where some are removed and some remain, but you would not want to try anything like that without professional input.

 

Thanks Dave. Yes I thought this would be needed. I was only going to attempt if consensus was 100% not required 

[tvrulesme]

Quick update after discussing with a structural engineer

 

As for the decorative beams, if the plasterboard is over the top of the beams it is most likely that they are not load bearing. As for the ceiling joists, these look like they have been replaced at some time and form part of the roof structure."

[Temp]

+1 to what @ProDave said.

 

The ceiling joists should/must be connected to the bottom ends of rafters. Check the roof is properly triangulated.  

 

Also check the span and dimensions of the ceiling joists as the "decorative" beams that run parallel to the ridge appear to be supporting them?

[tvrulesme]

9 minutes ago, Temp said:

+1 to what @ProDave said.

 

The ceiling joists should/must be connected to the bottom ends of rafters. Check the roof is properly triangulated.  

 

Also check the span and dimensions of the ceiling joists as the "decorative" beams that run parallel to the ridge appear to be supporting them?

 

 

Thanks a lot. Yes I am not sure they are attached so I was planning on connecting them before I remove anything.

 

I think the camera angle made it look as though the beams were supporting the joists. There was just a layer of plasterboard sandwiched between them and if the plasterboard was acting as structural support I'm in worse trouble than I thought. 

 

What would you use to connect the joists to rafters? coach bolts? Nervous of banging too hard with nails

[Temp]

Yes. For an outbuilding I used spike washers between the rafters snd joists and coach bolts.

[Gus Potter]

8 hours ago, tvrulesme said:

 

 

Thanks a lot. Yes I am not sure they are attached so I was planning on connecting them before I remove anything.

 

I think the camera angle made it look as though the beams were supporting the joists. There was just a layer of plasterboard sandwiched between them and if the plasterboard was acting as structural support I'm in worse trouble than I thought. 

 

What would you use to connect the joists to rafters? coach bolts? Nervous of banging too hard with nails

In these old timbers I would avoid nails too if possible. The timber will be well seasoned, quite hard possibly and already have a few splits etc in it.

 

The spiked (toothed) washers work well in new timber as it still quite soft, even some of the knots. But with old timber you really need to crank up the bolts to make the washer teeth bed in and form a close joint. You can easily do more harm than good to the old wood, it can split inder the bolt tension load and cause a headache.

 

I would look to see if you can use M12 bolts in cleanly drilled holes. As a ball park you want to look at putting 2 number bolts per joint with 50 x 50 x 3.0mm thick square washers under the head an nut. The trick here is to see if you can get the bolts in while maintaining the edge and end distances. See table below for a guide.

 

 

End distance is the distance from the bolt centreline to the cut end of the timber. Edge distance is the distance from the bolt centreline to the edge of the timber.  Unloaded means that the force in the bolt is acting away from the end or edge. Loaded means the bolt force is acting towards the edge or end. With a typical roof connection the timbers are at an angle so we are left with having to use the loaded values.

 

Sometimes this does not work so you look at M10 bolts.. then one larger bolt.. the joys!

 

Mull this over and have a word with your SE.

 

 

 

 

 

[Temp]

I had to use big square thick "washers"/plates to stop the heads and nuts being pulled in before the spike washers were seated. Once the spikes were in I replaced the big heavy plates with regular large round washers.