How deep should a joist be inserted into a wall?

[Krustycrab]

Hi,

I'm looking into replacing a couple of ground floor joists due to them being badly rotten and warped, probably due to a kitchen leak from the old owners. The small room is only 2 metres wide and the 2 old joists that i have removed where 4 x 2.

One end of the new joist will sit nicely into the wall and enter the wall about 4 inches deep but at the other end the gap where the old joist sat is only around 2 inches deep maximum.
Is 2 inches depth into the wall enough to hold the new joist or is there a minimum depth that it should enter the wall to make it solid / safe?

Thank you very much for you time, any advice is much appreciated.

 

[Softus]

2" isn't really enough. If it's bearing onto a brick then you run the risk of it fracturing, and in case 2" at the end of a joist puts a lot of reliance on that short section of the joist.

What's stopping you inserting it to a more decent depth, e.g. 4"?

 

[Krustycrab]

Hi,

Thank you for your reply.

It appears to me that the hole in the wall already has the end of a joist in it, from the living room. So both sides of these joists enter the brick to approx half way. I'm not sure if they are all like this or if it's just these few end joists. From what i can see the rest of the joists are whole lengths which run right through the length of the house. These 2 however are separate.

Are there any acceptable ways of strengthening these joists, maybe with a certain type of hanger?

Cheers

 

[Softus]

If it's always been like that then the other to look at it is that you wouldn't be making it any worse.

I know I'm backtracking here, but the risk would be worryingly greater if these were 1st floor joists - I'm thinking that if it were me I'd probably live with the risk and avoid putting a mound of grand pianos in that corner.

 

[Krustycrab]

I was hoping you'd say that.

To be perfectly honest it's a corner of the kitchen which is to be half covered in units anyway, it's not like it's a main walkthrough.

Thanks for your time i'll have a serious look before i actually decide on anything.

This may sound silly but just out of curiosity when people say that wood expands and contracts, are we just talking millimeters here, it never actually shrinks by any serious amount... does it?

 

[Softus]

This may sound silly but just out of curiosity when people say that wood expands and contracts, are we just talking millimeters here, it never actually shrinks by any serious amount... does it?

It can. That's the purpose of acclimatising it before using it.

For example, have you even seen traditional floorboards with huge gaps between the individual boards....

 

[Symptoms]

Krusty - a couple of methods:

1.
Brick-up existing 2" joist pocket, when set insert joist hanger. This has the advantage of preventing moisture leaching into the new timber (make sure it's treated). Use this method if there is any chance of the wall being 'damp'. Use welded hangers, not the cheaper pressed jobs if any chance of heavy loads on floor.

2.
Beef-up the bearing area of the existing joist pocket by attaching a timber 'wall-runner' level with the base of the pocket, effectively increasing the supporting area. This wall-runner could go the length of the wall to support the rest of the joists. Remember to allow effective air circulation space around joist ends within the pocket. I'd probably use this method for ease of installation.

 

[Krustycrab]

Thank you very much for all the replies.

A 'wall runner' sounds like the perfect solution if it's an acceptable method of strengthening them. I may as well run it the full length just for piece of mind anyway.

Thanks again, i very much appreciate your time.