just because you heighten the boards doesnt mean you gain that much strength. you essentially can double up the sides with 2x6 making a 4x6 basically leaving that small height difference to be covered by the subfloor. my concern is the span a 2x whatever is only going to span so far before it bows or breaks. remember you are adding not only the weight of the existing structure plus the new room plus the weight of the lumber for the floors and subfloor so a small span between load bearing walls like 12 ft is one thing here but anything more to constantly carry a higher load than the original house was designed for you need to make sure you can safely span this distance.

A rule of thumb for what size joists are needed is this. Any 2in thick joist will span a distance of 150% x its depth x 12. This means.

3x2 will span 4.5 feet

4x2 will span 6 feet

5x2 will span 7.5 feet

6x2 will span 9 feet etc. etc. etc.

This is assuming that the loading will not be more than what would be expected in any room of a domestic dwelling.

In your case why not put hangers fixed to the joists and screwed to the roof spars - this way the roof will be taking some of the weight you put on the floor.

You would do well to talk with someone experienced in framing to be sure you sister on the right size joists and in the proper way. The future load, the condition of the existing joists and the span all enter into the correct solution.

A 2x5 with a 2x3 attached to it would only have the mechanical strength of a 2x5. Unless you can come up with a means of bonding them that's as strong as the timber (and don't believe the superglue adverts)

Hello, my name is hanna, i am living in rome at the moment, I think this website can help you, My friend in viterbo had the same problem as you (all of the houses there are very old with legistical problems). she used cocontest. hope this helps! https://www.iubenda.com/privacy-policy/5...

Use less strength ceiling, or as according to desgin steps we use factor of safety it can resist to another way...

just sister them with a 2 x 8 and be done with it, glue and nail them and you won't have to give it another thought

Hello,

I am in the process of buying a house and will be looking at converting the attic to a storage/playroom but think I will have to re-enforce the ceiling joist to handle the weight. I understand that this can be done by sistering the joists but was wondering if I could simply increase the depth of the joists? For example, if the joists are 2x5 could I not glue and bolt a 2x3 length of timber on top of it effectively transforming it into a 2x8.

Any advice you can provide will be greatly appreciated.

Thanks