Hello!
Father-in-law has a deck. 17 x 3 meters. The carrier beams stand on piers at the front and are attached to the house wall at the back. The piers are about 2.5 meters high.
The floor joists are 45x195 on a span of 3 meters so that's all okay.
However, the carrier beam is 45x195 with a distance between the posts of about 2.40 m, which is not okay. At the same time, nothing has collapsed and the deck has been there at least since 2004 when the father-in-law bought the house.
The everyday problem is instead a bit too much sway in the decking. This is probably because it is 28x120 and the floor joists are about 90 cm apart.
I am considering adding more floor joists in between so it becomes about 45 cm apart and stops wobbling.
However, I am unsure if this could worsen the problem with the structurally incorrect distance between the piers, which should either be a maximum of 1.8 meters or have carrier beams at least 70x195 (if I have read the tables correctly).
Does anyone know how increasing the number of floor joists could affect the structural integrity? Is it better/safer to increase the thickness of the decking?
Grateful for any input.
Best regards, Pär
The carrying beam that is between/on the posts/piers can be doubled by attaching an additional 45*195 board so that it becomes 90*195. You may need to notch the board a bit, depending on how it looks.
I combined two 45*195s for the carrying beams, with about 2.8m between the piers. Then I have 45*145 for the floor joists, with about 2m between the carrying beams, using C/C60 for the floor joists. I have 120*28 decking.
Hello Demmpa and thanks for the tips. The problem is that the support beam rests in a notch on the pillars so setting 2x 45x195 probably won't work. See image. However, your suggestion made me think about whether it's possible to at least add another support beam with a smaller width next to it above the notch on top of the pillar. However, I can't bolt them together due to the fork anchor in the existing support beam. Thanks for the idea!!
Hi Demmpa and thanks for the tips. The problem is that the support beam rests in a notch on the pillars, so placing 2x 45x195 probably won't work. See picture.
However, your suggestion made me think about whether it is at least possible to add an additional support beam with a smaller width next to it above the notch on the pillar. However, I can't strap them together due to the fork anchor in the existing support beam.
Thanks for the idea!!
The pillars appear to be made of wood, so it's fairly easy to saw a notch in the pillars and attach a carrier beam. At the same time, you can saw a rounding on the pillars to prevent water from standing on them.
The new carrier beam can be recessed either flush with the existing ones (more difficult) or on the other side of the pillar (easier).
What determines the load on the supporting beams is their mutual distance and the distance between the piers. Increasing the number of floor joists only causes a marginal increase in the load on the supporting beams. 90 cm is far too long for 28x120 mm decking, I think 60 cm is the maximum for a comfortable feel. A 3 m span for 45x195 floor joists is on the borderline. However, the combination of a 3 m c/c distance and 2.4 m between the piers for the supporting beams is far too weak. There are two principles to solve the issue. 1) Double the supporting beams, i.e., 2 pcs 45x195 side by side. 2) Halve either the c/c distance or the pier distance.
