Splice glulam beam in intermediate floor

[Joakim88]

We live in an old Skånelänga with a renovated attic. The floor on the upper floor is noticeably shaky. The joists currently consist of timber beams that are 150mm thick and span 5.5m from outer wall to outer wall. The Cc varies from anywhere between 800 to 1500mm. After careful inspection, I have also determined that the floor structure rests loosely on the outer wall, neither attached to the wall nor the rafters.

Now we want to reinforce the floor structure as we will need to use the upper floor more in the future. We're considering adding an additional glulam beam in each section. The problem is that we have no way to bring in beams of full length because there are no windows or doors from the "right" direction, and they need to be longer than the full length of the room. Is it possible to splice a glulam beam in a reasonable way when it only has support at the ends? How is this best done, if possible?

 

[jonaserik]

It is not possible to make a hole in the ceiling right where the beam should be then. Not much is needed for the hole and it's easy to fix afterwards.

 

[justusandersson]

Glulam beams, like other beams, are jointed by adding pieces on both sides that are bolted together. The added pieces can be replaced with flat steel. The length of the added pieces should be about 1 meter. Nail joints can also be used, but in this case, it is not a suitable method. The effort is not proportional to the gain. The solutions you can consider are 1) making holes at the top edge of the outer walls on one side and sliding in the beams, 2) creating supports for the glulam beams on the inside of the walls through some form of horizontal beams, and 3) improving the stiffness of the existing beams by screwing and gluing wood on the height. This can be done in stages and can also include a subfloor in the form of chipboard or plywood. Altogether, approximately 100 mm of additional material is needed for acceptable deflection. There are quite a few people here on the Byggahus forum who have experience with Skånelängor and can contribute ideas.

 

[jonaserik]

The roof should be nailed in so that it is not visible. Join with angle irons 60X60 2 pcs X 2 pcs = 4 pcs and through bolts minimum 12 mm and as said 1 meter long with 3 bolts on each side of the joint. With cap nuts that lock + proper spring washer. Then turn the iron so that the flat part faces downward; this part is tension-resistant, and at the top, the iron is set with the flat part facing upward, compression-resistant. Don't be afraid to use heavy bolts; it is the shearing/cutting that they need to withstand.

 

[bossespecial]

I would advise against splicing freely supported beams as the final results are most likely not going to be better than they already are. I agree with the suggestions from @justusandersson

 

[Joakim88]

Glued laminated timber and other beams are joined using splice plates on both sides that are fastened with through bolts. You can replace the splice plates with flat steel. The length of the splice plates should be about 1 meter. You can also use nailed connections. In this case, however, it's not a suitable method. The effort doesn't justify the benefit. The solutions you can consider are 1) make a hole at the top edge of the outer walls on one side and slide in the beams, 2) create supports for the glued laminated beams on the inside of the walls using some form of horizontal support beams, and 3) improve the stiffness of the existing beams by screw-gluing wood on the vertical side. This can be done in stages and may also include a subfloor in the form of chipboard or plywood. In total, an additional 100 mm of material is needed for acceptable deflection. There are quite a few people here on the Byggahus forum who have experience with Skåne-style houses and can contribute ideas.

Thanks for a detailed answer! Do you know if timber logs, not glued laminated timber, work just as well if you go up 100mm in dimension, that is to about 250mm?

 

[justusandersson]

Yes, they do. I calculated it before I replied.

 

[Joakim88]

Yes they do. I calculated it before I replied.

Thank you, thank you!