French wood screw dimension for beam pergola

[Jocce81]

I'm going to build a small canopy, about 4x1 meters.

I plan to attach a 45x120 beam to the existing wall (where the "rafters" will rest against the wall of the house).

What dimensions do I need for the lag screws (which I plan to drive through the existing siding into the studs behind) and how many do I need?
Should I use washers? What kind of washers?

Should I pre-drill? How deep / what dimension?

Anything else to consider?

/Jocce

 

[Demmpa]

What does the existing wall look like? Picture?
What dimension does the stud behind the panel have?

 

[kniv]

Essve WAF screw instead of french. Better and you can skip the washer. The dimension is based on the shear stress breaking limit of the screw and your expected radial force on the screw.

 

[Jocce81]

How does the existing wall look? Picture? What dimension is the stud behind the panel?

How does the existing wall look? Picture? What dimension is the stud behind the panel?

Picture of the wall here (with "mockup" for approximate size of the screen roof) Studs: no idea about the size actually...and not super keen on removing the panel to check. But it's an insulated sunroom which this wall is the outside of, if any assumptions can be made from that?




/Jocce

 

[Jocce81]

Essve WAF screw instead of French. Better and you avoid the washer. The dimension is based on which shear stress fracture limit the screw has and your expected radial force on the screw.

No idea how to calculate that. Any ideas from the picture above?
(The dimensions of the timber will of course be thicker than this "mockup")


/Jocce

 

[kniv]

No idea how to calculate it. Any ideas from the image above?
(The dimensions of the timber will of course be larger than this "mockup")


/Jocce

Ah, that's quite small. Are you planning to use multiwall sheets? You probably don't need to calculate much for that.
What is the distance between the studs inside the wall? I think you'll easily see it by either removing the bottom panel or checking where the panel is nailed. How were you planning to find out where to screw (regardless of the screw)?

I would use Essve WAF 8mm, at least 100 long (a bit depending on what's behind/inside the wall). Provides 30mm attachment in the stud given 22mm panel. About 8 screws on 4m should be enough, a bit depending on where you can have the attachment points.
The largest regular load will come from the roof's weight. A little snow now and then will likely have a minimal impact on the load.

 

[Jocce81]

Ah that was very small. Are you going to use polycarbonate sheets? You probably don't need to do a lot of calculations for that.
What distance do you have between the studs inside the wall? I think the easiest way to see it is by either removing the bottom panel or checking where the panel is nailed. How were you planning to figure out where to screw (regardless of the screw)?

I would use Essve WAF 8mm, at least 100 long (depending a bit on what you have behind/inside the wall). Gives 30mm anchorage in the stud given 22mm panel. About 8 screws over 4m should be enough, slightly depending on where you can have the attachment points.
The greatest regular load will come from the roof's own weight. A little snow now and then probably has very little impact on the load

Yes, as mentioned, about 4x1 meters

Using corrugated metal sheets for the roof so no major weights.

I plan to check where the panel is nailed to see where the studs are, otherwise I’ll try with a stud finder (can check both from the inside and outside I think)

/Jocce

 

[Demmpa]

I would have installed at least two standing beams from the ground all the way up to the top rail to support the weight from the roof.

 

[Jocce81]

I would have placed at least two vertical studs from the ground all the way up to the beam to absorb the weight from the roof.

Instead of putting the load on the support beam against the wall?

/Jocce

 

[kniv]

Instead of placing the load on the support beam against the wall?

/Jocce

You can transfer the load from the support beam and wall fixation with vertical studs under the support beam.

 

[Jocce81]

You can alternate the load-bearing beam and wall attachment with standing studs under the load-bearing beam.

Do you think it's necessary for such a small roof?

/Jocce

 

[kniv]

Do you think it's needed on such a small roof?


/Jocce

No. If you can attach the bearing line to the studs in the wall and not just the panel, that's enough imo

 

[Jocce81]

No. If you can attach the load-bearing line to the studs in the wall and not just to the panel, it will be fine imo

That's kind of what I'm thinking too.

/Jocce