Avoiding Point Loading of HD Catnic Lintel?

[iDIY]

Long story short, I am building a garage with an art studio above it. Planning is sorted and the BCO has told me that other than the foundations which support both parts of the building, the garage level doesn't actually come under building regs for things like insulation etc, BR only apply to the art studio above.

As the dense concrete block cavity walls of the garage level have risen to the height required for suitable head clearance inside I find the roof joists of the garage which are the floor joists of the studio need to join the walls exactly where the HD catnic lintel crosses the doorway. As I understand it you can't point load the catnic lintel so the joists can't sit directly on the lintel.

So would it be ok to cross the vertical inner face of the lintel with a limber bearer and hang the joists from that?

See attached picture of the type of lintel and the proposed solution?

 

[johnny2007]

Yes, your solution is the standard installation.
You could even have just a shorter wallplate for where the lintel is and lie the rest of the joists in the blockwork.
Personally I prefer wallplates all the way.

 

[tony1851]

You can sit floor joists directly on top of a hd catnic. By 'point loads', they mean isolated beams coming onto the lintel, eg a heavy steel beam which might be supporting a masonry wall.
Although floor joists are technically point loads, the load under each joist is relatively small and for practical purposes can be regarded as a uniformly-distributed load.

 

[catlad]

And how would that lintle support the timber where the garage door was?

 

[iDIY]

And how would that lintle support the timber where the garage door was?

not sure I understand the question, can you elaborate?

 

[catlad]

I'm just looking at your diagram and I can't see how you can attach anything to that catnik

 

[iDIY]

I'm just looking at your diagram and I can't see how you can attach anything to that catnik

Good point.. I was thinking of a setup like this to transfer some of the sheer forces to the lintel. The rest being taken by the wall plate bolts through the adjacent block walls.

 

[tony1851]

How would you fix the inner timber plate to the back of the lintel? - I doubt Catnic would allow drilling and bolting to the back. In any case, they suggest filling the back of the lintel with blockwork or brickwork to maintain stiffness of the steel, which isof course relatively thin.
If your joists are coming in at the same level as the lintel, consider joist hangers.

 

[iDIY]

How would you fix the inner timber plate to the back of the lintel? - I doubt Catnic would allow drilling and bolting to the back. In any case, they suggest filling the back of the lintel with blockwork or brickwork to maintain stiffness of the steel, which isof course relatively thin.
If your joists are coming in at the same level as the lintel, consider joist hangers.

I wasn’t thinking of fixing it to the back of the lintel, just a bed of mortar to ensure the load is spread evenly, much like a wall top plate. It can’t come out because the wall plate timber is bolted to the block work and the joists are not able to move away from the wall plate either, because they are tight up against the wall plate at the other end. If it was blocks or brick on the inner side of the lintel they are not fixed to the vertical face they too are only ‘fixed’ on a bed of mortar.

my thought process being that using joist hangars is introducing the same point loading as putting the joist straight onto the lintel.

 

[^woody^]

Just don't use a catnic on the inside, use something else. I've heard that steel beams are quite good.

 

[johnny2007]

Install the lintel as normal and the blockwork as you didn't need joists.
Then, fit a wallplate to the blockwork and joist hangers as per your original sketch.
That's the standard way.

 

[iDIY]

Thanks all, I’m clearly thinking along the right lines with no definitive right or wrong answer. With that in mind I have sent the details in an email to the BCO with pictures to ask which he wants me to go with.

 

[tony1851]

my thought process being that using joist hangars is introducing the same point loading as putting the joist straight onto the lintel.

As mentioned before, the loads from floor joists are not regarded as point loads because of the relatively low loads. What would be regarded as point loads are steel beams carrying additional loads, or concrete beams from a beam-and-block floor.
You are over-thinking the issue.
I suspect you might have practicality issues trying to bed a timber member onto the bottom flange of the Catnic, and then fixing your timber wall-plate to that - or have I missed something?

 

[^woody^]

Install the lintel as normal and the blockwork as you didn't need joists.
Then, fit a wallplate to the blockwork and joist hangers as per your original sketch.
That's the standard way.

How are hangers fixed to a 2 or 3" wall plate in the standard way?

 

[^woody^]

As mentioned before, the loads from floor joists are not regarded as point loads because of the relatively low loads.

Do lintel makers say this too? Or do they specify a certain distance [of set] masonry before joists are laid? Asking for a friend.