What can and cannot be built? (loose timber)

[Snailman]

I was looking into something similar a while ago, here are some pictures of a method

http://www.tangberget.blogspot.com/ (bandtäckning)

Nowadays, I have switched to single-storey since the allowed building area has increased...

 

[imported_Byggaren]

Building a balcony on top of another part of a house is often called a risky construction.
Still, many home builders construct houses this way. See the pictures of examples from Myresjöhus and Floods wooden houses.

The question is, how do you secure this type of construction?

Over time, there is no 100% secure way to build such a balcony. Partly because materials wear out, and partly because the building 'lives' as it ages. It might remain watertight for 20 to 25 years, but then a stealthy leak starts before the homeowner discovers that it is no longer watertight.

Throughout history, people have tried to find materials and building methods that can handle horizontal watertightness. No one has succeeded yet, even though many believed they were close to the solution. Leakage will occur sooner or later, sometimes quite soon.

There are solutions with paper, rubber membranes, metal sheets, and other materials. Building systems like built-up with btg. in combination with these, etc.

The only way to be somewhat protected is to slope the base and build in two separate layers. The lower one slightly sloped to allow water drainage with the possibility of replacing the covering. The upper one horizontal, preferably detachable. But if the sloping is too flat (3-4 degrees) as the covering material allows, you can expect water on the roof. It requires significantly more to prevent snow, thaw, freezing, etc. from damaging the covering material (penetrating joints and lifting). A slope (>10 degrees) is close to a somewhat secure level. But wind pressure can still cause problems in several cases. Especially when the balcony lies with one side against a vertical surface (and I know no balcony that doesn't have such a side).

Another possibility is to build with natural materials that absorb moisture. There are several examples where such solutions have been more successful than technical ones. Among others, the old heating plant at Augustenborg (+ several houses in the area) in Malmö has been re-roofed with sedum. And a green floor on the balcony might not be such a bad thing to walk on?
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Byggaren

 

[Mikael_L]

Another possibility is to build with natural materials that absorb the wetness. There are several examples where such solutions have succeeded better than the technical ones. Among others, the old boiler house in the Augustenborg area (+ several houses in the area) in Malmö have been redone with sedum roofs. And a green floor on the balcony might not be so bad to step on?
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Byggaren

A sod roof with grass sounds pretty fun. Then I wouldn't need to build any decking to walk on either, grass between the toes feels nice. And if we get rabbits, we can just let them out on the balcony when they're hungry.

Well, there might be something to the talk about risk construction.

Regarding what snailman sent, it's a low-sloping metal covering, and I wouldn't attempt that myself, so I'd need to bring in a metalworker. The cost might end up being more than if I instead build an upper floor on the lower section and then place a completely open balcony outside of it (i.e., nothing under it).

If I can get hold of a large enough metal sheet, so there are no seams at all. Do you think it would be a project that someone without metalworking skills (I've only worked a little with car metal) could manage? And do you think a whole sheet would also reduce the risk of future problems...

... genius speculates, or whatever it was...

 

[imported_Byggaren]

Not even seam-welded stainless steel sheet lasts forever.

Finding such a large sheet in one piece will probably be difficult. The rolls are usually a meter wide at most. You will probably need a plåtis after all.
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Byggaren

 

[Mikael_L]

I think I should try to avoid a balcony above the living space then.

But now I have come up with a new question...

If you have a shed roof where the upper side connects to a higher building section. How do you handle the ventilation of the air gap? Is it those mold stoppers that connect out under the metal roof that are used then? Does that work well, even though the metal roof connects quite tightly to the wall above?

And what if it's a standing seam roof that lies completely flush against the sheathing!?

edit: I'll include a picture that highlights what I mean.

 

[macaroni]

Mikael L:
A model that I have seen is that the lower roof has an air gap that runs up to the upper wall and goes into the air gap. The transition is covered by a sheet metal covering. See picture!

 

[macaroni]

I want to return to the original question about span, floor joists, and load-bearing capacity.

I am going to build an upper floor on our existing single-story house.
The floor joists on the upper floor will span a length of 9 meters, and on the lower floor, I will install load-bearing walls and steel beams (14-18 cm H-beam), but to minimize the number of steel beams, I want to know the maximum span distance, i.e., the span.

Can a normally loaded floor with 220 mm joists handle a span of 4.5 m? I've heard that some house suppliers go up to 4.2 with c/c 60.

Is an 18 cm high H-beam sufficient as support? Glulam beams take up so much space in the ceiling. I don't want to make recesses in the joists. Too much work!

The building permit drawings are available at http://hem.fyristorg.com/warnby/bostad/

According to a thread I started earlier, it seems the Timber Guide doesn't like this. Apparently, as I understand the Timber Guide, a floor joist should not be longer than 7 meters. http://www.byggahus.se/forum/byggma...4-max-spaennvidd-pa-golvbjaelklag-220-mm.html

In that case, I am thinking of laying a 5-meter length from one direction and another from the other direction and nailing them together parallel. The c/c distance will still be 60 cm, but on one half of the house, it will be shifted slightly to the side. Should be doable, right? I made a little sketch of what I mean.

 

[imported_Byggaren]

If we account for 100 kg/sqm in uniformly distributed load (useful load) + self-weight and movable load of a person in the most dangerous loading position (mid-span) with a center-to-center spacing of 600 between the beams and consider that the long-term deformation determines the final dimension, a 45x220 is more than sufficient for this. (The roof structure must not load the floor in any part.)

A bending resistance (Wx) of approximately 285 cm^3 is required for the load (=> 45x195 in timber quality K24) + a notch upwards for the long-term deformation, and then we land quite precisely on a 45x220 in timber quality K24.

By nailing them together over the central support (as you show), you additionally gain extra stiffness in the floor (depending on how the nailing is done). The overlap, however, will not be more than half a meter along the beam's length, and that is too short to have the proper impact. The beam ends need to be extended to the point where the support moment changes sign, which is approximately 1.5 meters from the central support along the beam's length. Therefore, the beams would need to be 6.5 meters long to fully benefit from the splice joint. Then the floor can be calculated as continuously supported on three supports, where the support moment becomes the dimensioning factor.

Which HE-beams are then required to support the floor depends on the largest span and the possibility of central support. Measurements of beam length from inner edge wall to inner edge wall, measurements of house width from inner edge outer wall to inner edge outer wall, and measurements of the placement of any central support are required. It is not impossible to place a beam, which does not necessarily have to be an HE-profile (it can also be a square or rectangular hollow profile of type VKR, KKR, or RHS). What is required, however, is that this profile be fire-protectively clad since all load-bearing capacity in the iron disappears already at +620C. Then it is easier to glue gypsum boards on a hollow profile than to clad an HE-profile.

Then the load from the beam/beams must be handled and transferred down to the ground. What does the foundation look like that they will stand on? Can it handle the point loads (which can be calculated in several tons)?

Return with more details, and I will see what is needed. Also, show how you intend to carry out the roof construction.
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Byggaren

 

[macaroni]

Hello Builder!
Thanks for the responses.

The roof should be a shed roof with trusses running in the other direction, i.e., supported on the outer walls. The span is 7 meters and the slope is 6 degrees. I would prefer to avoid load-bearing walls there. I'd rather go with really thick Kerto or glulam beams. Dimension? Felt roof? Metal?

I haven't thought about the points for the support legs for the steel beams. That was a wise observation. I'll check this. Today, there are basement walls built on rock in most places.

Regards,
Marcus

 

[Mikael_L]

Mikael L: A model I have seen is that the lower roof has an air gap that runs up to the upper wall and goes into that air gap. The transition is covered by a metal flashing. See image!

Yes, that looks good. You also get the advantage of the sun's heating of the facade creating natural convection.