ᐅ Install a walkable ceiling, thickness of the rafters

Hello,

I would like to briefly introduce myself as this is my first, and maybe not my last, post in this forum.

I am from Rheinbach in Germany, near Bonn. I am 41 years old and currently renovating a half-timbered house. At the moment, all the ceilings are being removed because the ceiling height is not ideal 🙂 and I am quite tall 🙂 However, my question is mainly about the roof structure.

I want to install a walkable ceiling where later 22 mm (7/8 inch) thick OSB floor panels will be laid and screwed down. The beams will either be placed in joist hangers or directly on the half-timber frame on the left and right sides. The length of the beams will be about 4.5 m (15 feet).

My question is: how thick does the squared timber or rafter wood need to be? For example, would a beam measuring 15 x 15 cm (6 x 6 inches) or rafter timber 8 x 16 cm (3 x 6 inches) or less be sufficient? What is the minimum size? The area is not intended to be living space, just walkable. Or is there not much difference in load requirements between walkable and living space when dimensioning the beams?

Thank you very much for your help.

Only walkable? That means you don’t want to place anything there, just walk around? Or how should this be understood? 😕

Hello,

otherwise, I would have suggested a storage room. But I was able to find out a bit more. A carpenter told me that the bearing length multiplied by 0.5 would mean, in my case, a beam of 8 x 20 x 4 meters (8 x 20 x 13 feet) or 4.3 meters (14 feet) with the bearing.

Best regards

Hello SuperHorst,
A walkable ceiling is a load-bearing component; this modification to the building requires approval in NRW (North Rhine-Westphalia).

You should consult a structural engineer and have the beams (and their fixings) calculated – even if the carpenter’s experience initially provides good advice. A span of 4m (13 feet) is not necessarily easy to handle with wood alone; a glulam beam might be necessary (as mentioned, consult a structural engineer).

Hello,

I don’t quite understand. There are oak beams spanning 5.5 m (18 feet) with a total of 4 beams, and between them is clay mixed with wood. I would estimate the weight without the beams to be about 1.5 tons. The beams themselves measure 12 x 15 cm (5 x 6 inches). Now I want to place the wood beams in the opposite direction because this way I have less span and can triple the number of beams using 8 x 20 cm (3 x 8 inches) beams over 4 m (13 feet). And now I have to worry about the structural calculations? Seriously?

I know what I’m doing. I will put the old beams back in, apply the clay mixture again between them, and then finish it all with a coat.

Regards

As mentioned, Superhorst, ceiling beams are load-bearing components > state building regulations = law, seriously; it may well be that the whole structure carries the load, but it still has to be calculated according to the law.