Roof ceiling joist strengthening.

[Carrerahill]

1 hour ago, alexbr said:

so got email from engineer to double them with 2x6, and change binder to 2x6.

Could you explain me how is " SPLICE THE CONNECTIONS WITH 1 METRE MIN SPLICED TIMBER SECTIONS" looks like. 

 

Ask him for a detail or sketch and for fixing details and types. 

[Gordo]

That sounds plausible enough upgrade to address sagging ceiling. Don’t think it will help with sagging rafters. Best use liberal wood glue and screw fixings to existing timbers and best avoid or at least keep splicing to end 1/4 of spans (defiantly not in centre). To fix properly to existing timbers the spliced timbers would have to be butt jointed and then spliced with a 2m length of timber I would suggest.

Edited January 13, 2022 by Gordo

[Gordo]

Some 8x2” collar ties bolted to say every 3rd rafter at purlin level should help rafters would help a good bit

Edited January 13, 2022 by Gordo

[alexbr]

can i put some new joists under the rafters like in picture, because the way some of the old joists overlap each other that I can't atach the new joists on normal side only the rafters side, the engineer said is not recommended, but don't really know how to do it differently. i could ask engineer a gain but it takes 2 days to get answer.

[Gordo]

On 19/01/2022 at 11:39, alexbr said:

can i put some new joists under the rafters like in picture, because the way some of the old joists overlap each other that I can't atach the new joists on normal side only the rafters side, the engineer said is not recommended,

 

You don’t have an issue with roof spread? therefore you do not really need to fix the new ceiling ties to rafters. That job is already being done by existing timbers and nail fixings. Therefore I wouldn’t see any issue in doing it as per the photo. However make sure you glue/nail/screw timbers together as advised by engineer to structurally work together.

Edited January 24, 2022 by Gordo

[SuperPav]

Firstly I am not a structural engineer so in the absence of any insurance/survey etc. always go with the engineer's recommendations....

 

However...  what I would do if all I wanted was a level ceiling would be as mentioned above, just attach straight 4x2's to the existing ceiling joists. Don't worry too much about their attachment to the wall or the rafter, you're still ultimately relying on the tensile strength of the original joists for the roof, all you're doing with the 4x2's is creating a level platform for the plasterboard.

 

Personally what I would then do is add struts from the existing roof rafters to a single point above the spine wall/rsj in the middle rather than where they currently go midspan in a room!

You will lose flat walking space in the loft, but it will channel any additional roof loads into a part of the ceiling/wall which can't sag, so will stop the ceiling sagging in the same place in the future.

 

 

Do NOT notch, cut or in any other way reduce the strength of the existing joists - they are quite possibly just about fine as they are (other than sagging) but are woefully undersized by modern standards so don't tempt fate.