Attaching floor joists with joist hangers on a crawl space

[thomasonit]

I am planning to build an extension of 6x4.5m to the house, which will be on a masonry crawl space. However, I am considering if I can avoid double-masonry against the existing crawl space and instead attach the floor joists with joist hangers directly to the existing crawl space. Is this acceptable according to proper standards?

 

[Dr Trä]

Yep, that's how you always do it

 

[Dr Trä]

By the way, shouldn't you attach the beam shoes to the existing joists? Or did you mean the wall?

 

[thomasonit]

Thank you for the quick response.

The extension will have the floor lowered by one step approximately 15 cm, which means that I will then need to attach with a joist hanger to the wall. Is that okay?

 

[Dr Trä]

Oh okay. No, you can't attach the joist hangers directly to the wall, you need to anchor a beam to the wall first and then the joist hangers. What material is the wall made of? If it's leca, it is difficult to get a good grip. But if you do that, you should be able to place support on the existing foundation with posts up to the new floor structure, as the foundation presumably extends about 10 cm from the wall? If that doesn't work, then unfortunately, it's probably going to require some masonry work.

 

[thomasonit]

The existing house was built in the late 50s, and I believe the blocks are some form of lightweight concrete, but not leca. But it sounds like building up is the best option according to you. A follow-up question I have is whether I should anchor the new crawl space foundation to the existing one with reinforcement (drilled in)?

 

[Dr Trä]

Do you have any base to build on next to the wall, or do you need to pour a new footing there? Well, I don't think it's necessary to anchor the wall into the wall. But I would probably attach the new floor structure to the existing wall with appropriate fasteners.

 

[thomasonit]

I will probably have to cast a new foundation in that case if it's going to be built. Ok, so you had anchored a beam in the wall and attached the joists to it? The question is just what the supports should consist of. I assume there should be as little wood in the crawl space as possible.

 

[haavard]

Long beam hangers hanging down from existing joists?

 

[Dr Trä]

Yep, I would have done that so you can adjust the studs if they are warped. You probably don't need wooden supports if you're laying bricks. But it feels like you want to anchor the new in the old in some way.

 

[thomasonit]

Interesting, yes it might be a good alternative, but are there such long balkskor?

 

[Dr Trä]

I have not seen that it exists.

 

[haavard]

Joist hanger for masonite beam is available in 500 mm.

 

[thomasonit]

Ok, thanks for the info.