Sistering a joist - how to fix to wall

[WillMase93]

Hi all,

We want to add a bathroom upstairs where there wasn't one before. As well as moving the hot water cylinder up there. I had a structural engineer round to work things out. If we just want the bathroom, no strengthening is required. If we want the bathroom and the cylinder, we need to double up 2 of the joists.

This is a rough overview of the bathroom:


The engineers request:


The left side as you look at the picture is easy, the top of that wall can be completely exposed, by lifting the floorboards so I can just sit the joist on top and bolt it to the existing. The issue comes with the right hand side, this is the party wall with my neighbour. Of course I need a party wall agreement, but how do I fix the new joists to the wall?

Here is a photo of the 2 existing joists where they are socketed into the wall:



Here is where I need some help. I see these options:

1. Widen the pocket in the brickwork where the existing joists go to take both of the new joists. Messy but doable. Any advice? I was thinking to stitch drill a bunch of holes (100mm deep?) and then knock it out with a hammer and chisel.
2. Some sort of hanger that I can fix to masonry. This seems impossible? The only one I think could work is a double width timber to masonry hanger. But to get it around both of them I need access from below, which I really want to avoid.

Is there any other option? Fixing a rim joist/wall plate and using a timber to timber hanger I don't think will be acceptable because it can only be in the space between the 2 joists which surely is not enough.

The existing joists are 'true' 2"x7"s i.e. 51mm x 177mm, the nearest standard size seems to be 47 x 175mm. Will this be ok, if so do I make the new joists flush with the top of the existing joists (so a gap below), or flush with the bottom and they are not flush at the top. If not, do I need to contact a mill and get them to cut me some true 2x7s?

I appreciate any advice, thanks.

 

[WillMase93]

Would something like this work?

47175WMHS - Welded Masonry Joist Hangers – Stainless Steel 47 x 175 47175WMHS - TIMco 47175WMHS

47175WMHS Welded Masonry Joist Hangers – Stainless Steel 47 x 175 47175WMHS Masonry Hanger - Stainless Free delivery over £80

yorkshirefixings.co.uk

If the flange is level with some mortar, to rake it out. Put the flange in and then fill it back up with mortar. Wait for it to cure and will it be fine?

 

[^woody^]

That's way over designed.

You don't need the exact same size joists you can fit smaller ones. You probably want to fit them slightly higher than the plasterboard anyway.

Yes, use those masonry hangers, and notch the joists to suit. They don't need to be stainless steel!

 

[WillMase93]

That's way over designed.

You don't need the exact same size joists you can fit smaller ones. You probably want to fit them slightly higher than the plasterboard anyway.

Yes, use those masonry hangers, and notch the joists to suit. They don't need to be stainless steel!

Thanks I appreciate your reply. Do you mean you think the strengthening unnecessary? I’m just going with what the engineer says.

Thanks those hangers look like a winner. What do you mean by notch the joists? I know what notching joists is. But why would I need to notch them?

 

[^woody^]

The engineer is covering himself. Domestic cylinders (and baths) are commonly just sat on a couple of single floor joists.

But if you want piece of mind by doubling them up, you certainly don't need to use the exact size joist nor have it flush with the top of the existing joist.