Trusses that are sagging

[M@ZE]

I'm currently starting to insulate and drywall the garage on the ground floor. Since it has been cc120 between the roof trusses and I want to have insulation in the floor/ceiling up to the attic, I ordered Finger jointed 6.5m 45x145 so I get cc60 and more stability when I screw on the particle board later.

Now to what I discovered, it looks like the roof trusses have started to sag a bit downwards when I looked up today, see picture. A bit worried, of course. Is there anyone who has tips on what I should do besides putting extra beams/supports between each truss?

 

[OpiMaza]

Is it something you have built yourself or have you bought them ready-made?

 

[M@ZE]

Is it something you built yourself or did you buy them ready-made?

It was the carpenters who built the garage who made the roof trusses. Skilled and professional, I assume that they calculated the dimensions, etc. when they put up the garage about 10 years ago.

 

[OpiMaza]

It's the carpenters who built the garage who constructed the roof trusses. Skilled and professional, I assume they calculated the dimensions, etc., when they installed the garage about 10 years ago.

A certain "deflection" is acceptable when it comes to roof trusses. A bit concerning now since it's summer and no snow, and they are deflected. If they have calculated it, then there shouldn't be any danger as it has held for 10 years. I would probably contact the company that did it and ask how they calculated it. As it looks in the picture, it seems a bit off since there are no nail plates on all sides of the truss.

 

[M@ZE]

A certain "deflection" is acceptable when it comes to roof trusses. It's a bit worrisome now that it's summer and there's no snow and they are deflected. If they have calculated it, then it's probably no danger, and it has lasted 10 years. I would probably contact the company that did it and ask how they calculated it. The way it looks in the picture, it looks a bit B since there are no nail plates on all sides of the truss.

I agree, the nail plates are on the other side and only on one as you say, and I agree that it doesn't look tip-top. Something I will complement. It's hard to say how much it sags, I don't know exactly how to measure it properly. But the idea is to insert extra beams between each truss and then batten with 45x70 across the trusses/beams to get an extra 70mm of insulation in the floor before screwing on the chipboards. However, is it only the existing trusses that bear all the load from the roof/snow even if I do as I've planned above?

 

[mexitegel]

No, your new 45x145 studs make no difference to the load-bearing capacity of the trusses. And you probably would have been fine without them for your floor as well, unless you're planning to put heavy things up there. Possibly, you should have placed your 45x70 studs with a center-to-center distance of 400 mm. But now there likely won't be any risk

 

[mlkjhr]

The 45x70 plus glued screw floor chipboard will distribute the load better so it's probably not a problem, as they have held up for 10 years.

 

[M@ZE]

No, your new 45x145 beams don't make any difference in the load-bearing capacity of the trusses. And you probably would have managed without them for your floor too if you don't plan to have heavy things up there. Possibly you should have placed your 45x70 with c-c 400 mm. But now there shouldn't be any risk

Yeah, I didn't dare to take a chance, so I ordered them anyway to be on the safe side . No, there won't be anything super heavy up there, just simple small things, etc. So I shouldn't worry about them flexing and just proceed as planned?

 

[M@ZE]

The 45x70 plus screwed and glued floor chipboard will distribute the load better, so it's probably not a problem, they have, as mentioned, held for 10 years.

Exactly, they have held for quite a while, although that's not a guarantee . But as you say, it should distribute everything better with cross-bracing and the chipboard. It might be a bit strange later when screwing the chipboard if every other beam is lower than the new ones I put in

 

[M@ZE]

Another question, how do you attach the new beams? Angle irons on each side and screw into the hammarband?

I was just thinking of letting them go as far so they just go over the hammarband.

Or something like this that screws down into the hammarband and then into the sides of the joist/beam?

 

[mlkjhr]

Yes, joist hangers are probably the easiest to use.

 

[justusandersson]

45x145 cannot span 6.5 meters even with minimal load without bending significantly. They don't contribute anything, rather the opposite. The original trusses have a stiffer construction with braces connecting the top and bottom chords. Even they are not intended for any significant load, at most 50 kg/sqm. You should not place any particleboard on top, it only increases the dead weight. If you want to make the attic usable as storage, you need to install glulam beams between the trusses.

 

[M@ZE]

45x145 cannot span 6.5 meters even with minimal load without bending significantly. They add nothing, rather the opposite. The original trusses have a stiffer construction with support legs that connect the upper and lower frame. They are also not intended for any significant load, at most 50 kg/sqm. You should not place any chipboard on top, it only increases the dead weight. If you want to make the attic usable as storage, you must install glulam beams between the trusses.

Oh no, then I have ordered mine in vain I wasn't planning to store anything super heavy up there, just the kids' snowracers and so on. This puts everything I planned to do out of play, are you sure of what you are saying?

 

[M@ZE]

C24 according to Moelven’s own website

http://www.moelven.com/se/Produkter...ruktionsvirke/Reglar/Regel-C24-Fingerskarvad/

 

[justusandersson]

are you absolutely sure about what you're saying?

Yes. You cannot store anything that weighs even the slightest up there. Use light insulation and do not lay any flooring on top. 6.5 meters is an incredibly long span for that dimension. The beams will bend down at least 6 mm just due to their own weight. If you want to increase the load-bearing capacity, you need to supplement with glulam beams at specified intervals.