Adding joists under a hallway floor

[jon ccc]

Hello
I want to add more joists to give further support to my hallway floor, but was unsure whether to:
1. attach wooden beams to the walls, and support the joists on them. [and what dimensions for the new joists and beams]

or

2. Cut out holes in the brickwork and stone wall, and rest the joists in the hole. If too many holes are cut, I was concerned about the integrity of the wall after reading a thread highlighting this [and what dimensions for the new joists]

Which approach is better?
i will be installing the new joists on their side, that is the width is on the horizontal like joist 2


The two joists holding up my hallway floor are 3metres apart. The hallway from wall to wall is approx 120cm.
Ive included photos of the joists underneath.
Joist 1 was installed normally, and so is 20cm wide and 7cm deep.
Joist 2 was installed on its side and so is 7cm wide and 20 cm deep.
The house is built around 1920, all the wood looks to be the original wood, from when first built.
Thanks

 

[theprinceofdarkness]

Looking the pics, I think what you calling Joists are actually bearers. The floorboards are fixed to the joists and the joists then rest on the bearers. i would use joist hangers. You scratch out about 6" of a mortar course and insert the hanger in the slot then make good the slot with mortar. the "joist" is then dropped in from above. Your problem is that you have no top access.
I would use 6" X 2" at 1m centres so to knock out the brick work would mean two bricks high in four places. Which is OK but a lot of work, when all you really need are some big brackets screwed and plugged into the walls (not available in the 1920s).
Going back to masonary type joist hangers, if you cut through the bit that the joist sits on then you can slid a half hangar on each side, then the other half hanger. then neat the bottom of the split hanger (say 1/2") and in from the wall side, drill a 6mm hole right through the whole lot, then put a 6mm HT bolt with washers through the hole to clamp the thing up tight. The joist should be a tight fit and needs to be tapped into the gap. make good the slot. With a crow bar lift the joist by 1mm and slip in a piece of material (could be as thick as you like, up to say 6") to support the joist against the new bearer.
Frank

 

[jon ccc]

hi Frank
thanks for yr advice.
i forgot to add that the cellar under the hallway floor is 6 foot high.
so i want to lay the new joists on the side for more headroom.
ive looked online but cant find horizontal floor joist hangers or their equivalent, unless they are under a different name. would you know of any?

 

[theprinceofdarkness]

If you lay a joist on its side, you are reducing its "strength" or increasing its deflection by an enormous amount. For a 4 X2, its 1/16 for a 6 X 2 its 1/81.
Frank

 

[jon ccc]

how do i make the uneven stone wall level, so i can put the joist hangers on the wall?
[ i looked online and youtube, but found little adivce]
thanks