Joist hanging options

[cosmarchy]

Hi,

I'm looking for some options with installing some joists for my loft.

I have a loft space which is approx 5m x 3m (and tall enough to stand) and want to hang some joists to make use of the storage space.

I don't fancy cutting holes in the walls as firstly they are partition walls between neighbours and getting a 5m piece of wood in a hole either side wouldn't be possible and that the walls are old solid red brick so no cavity.

So, my options appear to be a ledger beam or joist hangers. I like the idea of a ledger beam as it should be easier to fix them level but not sure whether these are structurally suitable as fixing the ledger board would be interesting with soft red brick.

Hangers may require backing under the wood to get the joists level if these are installed in the mortar joints which aren't too bad but not as level as a you'd expect on a modern building.

Any ideas or thoughts? I know this will be a bit challenging but I'd rather have a structurally sound solution...

 

[^woody^]

All those are options, but to comment on whether they are suitable options for the situation will need you to post up some images or a sketch showing the loft arrangement.

 

[Mrs Ten Names]

Research Atlas fixings, epoxy fixings and rawlbolts fixings for fixing a ledger beam.

 

[cdbe]

You would normally span the shortest span.

 

[cosmarchy]

All those are options, but to comment on whether they are suitable options for the situation will need you to post up some images or a sketch showing the loft arrangement.

Empty space in the roof so was looking to do something as simple as this. The yellow lines would be the ledger boards as these are adjoining walls to neighbouring properties. Depending on where this sits in the roof space, I may have to go around the chimney breast.

Research Atlas fixings, epoxy fixings and rawlbolts fixings for fixing a ledger beam.

Shall do, thanks

You would normally span the shortest span.

I agree but with reference to the image above I'm not sure this is an option as the shortest span (3m) would be going from the front of the property to the rear which means spanning between the red lines. I only have 3m due to the pitch and layout of the roof internals. I would need something substantial to fix the red lines to the side walls so still need some fixing method.

My initial thoughts were to run the joists across the property (in the direction of the red lines) as although the longest span, I could fix every joist at each end whether that be to a hoist hanger or ledger board. This way the loading is shared across multiple fixings at end of each joist.
If however I put two joists where the red lines are and then use the shortest span (in the direction of the yellow lines) all the weight is off four fixings at the ends of each of the red lines.

 

[^woody^]

Ledger board and hangers would do. Normal fixings, no need for resin.

At that length of unsupported span, you'll probably need to drop some hangers from the rafters, mid or third span.

 

[cosmarchy]

Ledger board and hangers would do. Normal fixings, no need for resin.

At that length of unsupported span, you'll probably need to drop some hangers from the rafters, mid or third span.

Thanks. I'm not looking to put much weight other than typical loft items but more concerned with supporting the weight of the timber itself.

Due to the awkward design of the loft I cannot go between the shortest spans which would have been ideal.

 

[^woody^]

Yes, that's why you'll liklihood likely need to drop hangers down from the rafters at mid or third span.

 

[cosmarchy]

Yes, that's why you'll liklihood likely need to drop hangers down from the rafters at mid or third span.

What about if I were to double or triple the red lines so that they are effectively forming something like 6"x9" and then run 2"x9" in the direction of the yellow lines as this is the shorter span?

Any advantages in doing that?

 

[Mrs Ten Names]

What about if I were to double or triple the red lines so that they are effectively forming something like 6"x9" and then run 2"x9" in the direction of the yellow lines as this is the shorter span?

Any advantages in doing that?

I'm not a structural engineer, and I have no training in that area.

By your diagram, is it correct to assume that this space is currently open to the rafters, (judging by the existence and position of the Velux window in your diagram)?
As others have said the usual method would be to span the shortest with your joists, (red in your diagram)
In your situation, that's not possible.
So ledger boards (yellow in your diagram) fixed to the shorter span is your preferred method. That determines the size of the 5 metre joists as 63mm X 220mm at 400mm centres, (8 joists) and at the lowest dead load, with Class C16 (according to TRADA tables).
You could use 50mm X 220mm C24 joists. This might impact the available head height in that area.
I do not know what size the ledger boards need to be. I would suggest you seek professional advice.
There are possibly other alternatives available.
You do not know how that area might be used in the future.
You're obviously not using any Building Inspector's approval. I don't know if any is required.

There's no point in doubling up the joists, they're sized to support the the weight as individuals.

In my opinion, there's no point, in fact I would advise against doubling up the ledger boards.
To my mind, the ledger boards rely on the sheer strength of the fixings to the wall. You don't want to put any additional turning load on those ledger boards by increasing the thickness of the ledger board.
Doubling up is designed for supporting 'headers' where both ends are fully and properly supported.

 

[^woody^]

What about if I were to double or triple the red lines so that they are effectively forming something like 6"x9" and then run 2"x9" in the direction of the yellow lines as this is the shorter span?

Any advantages in doing that?

Then you're into the realms of guessing not designing.

Why can't you use the rafters or that partition wall for support?

TBH though, that 3d drawing is not clear. It's showing a room in the roof and what looks like a tiny bit of room in the apex that you are trying to form a floor, and this floor going through a roof window.

A section would be clearer