Problem with roof concept

[MrtnBuilder]

Hi,

According to the administrative decision, we must have a pitched roof with a slope of between 30 and 45 degrees.

 

The roof surfaces can have different slopes; it's important that they are within the 30-45 degree range.

 

We currently have a foundation slab, along with the underfloor heating system and the sewage system.

 

I've marked the sewage outlets with red circles on the ground floor plan.

 

The attached document also includes the floor system design. We can only move the ground floor walls so as not to encroach on the underfloor heating system.

 

As I mentioned, the problem arises with the roof. The building is rectangular in shape with an attached garage.

 

Due to the administrative decision, the building's height, measured from the entrance to the roof ridge, including the roof layers, cannot exceed 950 centimeters.

 

We planned a hipped roof on the building, but it's not possible. Here's why:

 

The building has two floors, each 290 centimeters high.

 

With a total height of 950 centimeters, we're left with 370 centimeters for the roof, including the ceiling between the floors.

 

(290 + 290 = 580)

(950 - 580 = 370)

 

The building has a front elevation of 1611 centimeters and a side elevation of 1186 centimeters.

 

We can't create a hipped roof on the building because the facades are too long and the roof is too high.

 

The only solution I came up with was a multi-pitched roof. Unfortunately, I'm not an expert in this field, so I have no idea what such a roof should look like if the entire building, including the roof, was below 950 centimeters.

 

The ground floor drawing shows walls. The elements drawn with dashed lines are beams that could also support the roof.

 

We plan to build a roof using prefabricated trusses.

 

Do you have any ideas on how to solve this problem?

 

Thank you for your help.

[JiAngelo]

Where's the problem?

30-45 degrees equals 7/12 to 12/12.

 

Side elevation 1186 ÷ 2 = 593 run

 And 370 rise ÷ 593 run = 7-1/2 pitch.

A 7/12 pitch = 342.37 rise.  This gives you room for lumber and shingles.

 

Try 7/12 front to back and make the front gable 7/12 as well initially.  Then increase the front gable pitch without the ridge exceeding the 7/12 ridge.

 

Here's an image in case the above isn't clear.

A 7/12 all hipped roof should work fine too. 

Girder over the heated floor areas so that all trusses bear on ex. outside foundation walls.

Edited 7 hours ago by JiAngelo
Errors

[MrtnBuilder]

Thank you very much for your answer.

 

With a single hipped roof, as you wrote, the height will be 343 centimeters.

 

Assuming the rooms are 290 centimeters each:

 

(290 + 290 + 342) = 922 centimeters.

 

Assuming we have 922 centimeters, it will be difficult to fit the ceiling between the floors and the roof finishing layers.

 

The ceiling between the floors will be approximately 40 centimeters (a wooden ceiling with acoustic insulation layers and underfloor heating on the first floor).

 

In this situation, after adding 40 centimeters, we have a total of 962 centimeters without the roof finishing layers.

 

Unless I'm miscalculating and misunderstanding something?

 

In this situation, unfortunately, the roof would be 30 centimeters higher than the administrative requirements, which state that the maximum height of the building cannot exceed 950 centimeters.

 

Is there any way to divide the hipped roof into smaller sections, which would reduce the roof span and its height to the ridge?

 

Thank you again for your help.

Edited 6 hours ago by MrtnBuilder

[MrtnBuilder]

the height of the rooms is 290 centimeters because we intend to install a mechanical ventilation system and install beams in the suspended ceilings, after lowering 20 centimeters for the installation, there will be 270 centimeters of clear height in each room.

[Joe_Carrick]

In most jurisdictions the building height is calculated to the average roof height, not the ridge.  Double check the local codes.

I also note that 270 cm is approximately 9 ft.  Do you really need that much ceiling ht for the entire floor area?  Ducts can be run in just central room ceiling as well as in the attic, depending on the design.

[MrtnBuilder]

15 minutes ago, Joe_Carrick said:

W większości jurysdykcji wysokość budynku oblicza się na podstawie średniej wysokości dachu, a nie kalenicy. Sprawdź dokładnie lokalne przepisy.

Zauważam również, że 270 cm to około 9 stóp. Czy naprawdę potrzebujesz aż tyle sufitu na całą powierzchnię podłogi? Kanały wentylacyjne można poprowadzić zarówno w suficie centralnego pomieszczenia, jak i na poddaszu, w zależności od projektu.

 

Unfortunately, in Poland, the building height is measured from the lowest point of the building entrance to the roof ridge, including the roof finishing layers.

 

Regarding the roof height, assuming I'm 30-40 centimeters short, I would have to lower both rooms by 20 centimeters. Unfortunately, I don't know why, but I have a ceiling joist in every significant place where ventilation ducts could be passed through, so after talking to the contractors, they said I would need to lower the ceiling. It's also possible that sewage pipes would be required in some places in the ceiling, so the room height is such that we don't have to worry about the height of the building and the rooms.

 

Regarding the sewage system, it's possible that a ceiling passage will be required because the design was changed after the sewage system and foundation slab were installed.

 

Unfortunately, we had to terminate the contract with the company that was supposed to build the building due to constant delays. They then stole the money we paid for the materials and fled the construction site.

 

We had to change the design to be able to financially continue the investment, hence the extra height in the rooms.

 

[Joe_Carrick]

Have you considered using open web floor joists so the utilities could be run thru?  That might help.save 20 cm.  It might also be possible to change the direction of floor framing in some areas to accommodate duct running between the joists.

[JiAngelo]

It appears the 950cm is to be measured from ground level outside the entrance, not the sill of the entrance itself.  If that is true, what is the elevation difference between ground level and top of the first floor deck (entrance sill.)? 

[MrtnBuilder]

11 minutes ago, Joe_Carrick said:

Czy rozważałeś zastosowanie belek stropowych z otwartym środnikiem, aby umożliwić poprowadzenie mediów? To mogłoby pomóc, oszczędzając 20 cm. Możliwe byłoby również zmienienie kierunku konstrukcji stropu w niektórych miejscach, aby umożliwić poprowadzenie kanałów między belkami.

 

The plan I attached at the beginning included truss beams. Unfortunately, intermediate beams supporting the ceiling must run beneath these beams (these are the beams shown on the plan as dashed lines), so I'm not sure if it makes sense to do this, since I'll have to lower the ceiling anyway to accommodate the beams supporting the trusses. Another option was to place the supporting beams directly into the truss, but in that case, it would block the access to the utilities. I don't know what to do in this situation.

After the company stole my money, I'm left to my own devices and don't know how to handle all this. I encounter problems with every solution. I'm starting to doubt whether this building can even be built given the 950-centimeter maximum height

Edited 5 hours ago by MrtnBuilder

[MrtnBuilder]

8 minutes ago, JiAngelo said:

Wygląda na to, że 950 cm należy mierzyć od poziomu gruntu przed wejściem, a nie od progu samego wejścia. Jeśli to prawda, jaka jest różnica wysokości między poziomem gruntu a szczytem tarasu na pierwszym piętrze (progiem wejściowym)? 

 

That's exactly what they came up with, which isn't very smart because the foundation should be slightly higher. In my case, the ground is sandy, so it's only 10 centimeters lower than the entrance to the building, but there will also be a terrace on the ground, so the design shows that the ground is level with the entrance to the building, therefore the ground and the entrance to the building are at the same height.

[MrtnBuilder]

2 hours ago, JiAngelo said:

Where's the problem?

30-45 degrees equals 7/12 to 12/12.

 

Side elevation 1186 ÷ 2 = 593 run

 And 370 rise ÷ 593 run = 7-1/2 pitch.

A 7/12 pitch = 342.37 rise.  This gives you room for lumber and shingles.

 

Try 7/12 front to back and make the front gable 7/12 as well initially.  Then increase the front gable pitch without the ridge exceeding the 7/12 ridge.

 

Here's an image in case the above isn't clear.

A 7/12 all hipped roof should work fine too. 

Girder over the heated floor areas so that all trusses bear on ex. outside foundation walls.

 

In this difficult situation, is there any other option to divide this hipped roof into several smaller sections, which would allow for a lower height to the ridge? Unless dividing the roof would require the roof to be constructed individually, rather than using prefabricated trusses?

In that case, I'm not sure it makes sense to do it at all, as the roof would be extremely expensive if the prefabricated trusses had to be abandoned

[JiAngelo]

I think Poland permits mansard roofs.

I specified 2900mm for each floor, 400mm for the second deck and changed the roof pitch to 2 degrees at 9000mm.  I added a decorative perimeter rail above the 9000mm point that still manages to be under 9500mm from the first floor deck.  The roof itself allows grade to be 430mm below the front door and you will still meet the authority requirements.

 

 

 

 

[JKEdmo]

6 hours ago, MrtnBuilder said:

The only solution I came up with was a multi-pitched roof.

Immediately thought of a mansard roof.  I'd imagine there's precedent for it in Poland.  Perhaps it can work in your case.

 

[MrtnBuilder]

I was thinking about a mansard roof, but from what I've read, the first part of a mansard roof has a high pitch, often 50-60 degrees, and unfortunately, in my case, only a pitched roof with a pitch of 30-45 degrees is permitted.

 

Does a mansard roof that only covers this range make sense? Is it even possible to create such a roof with only this pitch?

 

The building authorities also state that flat roofs with pitches of up to 10 degrees are permitted, but they can be used on a maximum of 50% of the roof surface.

 

Unfortunately, the problem with this roof is that I don't know how I could connect it to a hipped roof. In this case, the hipped roof wall would have to be higher to extend the membrane from the flat roof to the hipped roof wall.

 

In this situation, would the height of the rooms above the hipped roof have to be even greater?

 

Because if the flat roof is lower, there will again be a problem with the height of the rooms under this roof

[JKEdmo]

If the steep lower part of the mansard roof is in fact part of the second floor construction / perimeter then maybe it can be interpreted as "wall" rather than roof?  This would be a discussion with your planning / building officials.  I would contact them and see if the planning code can be flexibly interpreted to help your design.  Just a thought.

[MrtnBuilder]

28 minutes ago, JKEdmo said:

Jeśli stroma, dolna część dachu mansardowego jest w rzeczywistości częścią konstrukcji/obwodu drugiego piętra, to może można ją interpretować jako „ścianę”, a nie dach? Należy omówić to z urzędnikami ds. planowania/budownictwa. Skontaktowałbym się z nimi i sprawdził, czy przepisy planistyczne można elastycznie zinterpretować, aby ułatwić projekt. Tak tylko pomyślałem.

 

The administration allows a maximum of two floors in a building, so if we already have two floors, even the side part of the mansard roof is unfortunately counted as a roof.

 

Unfortunately, in Poland, such situations are not easily resolved by the authorities. Our officials usually don't help the investor, quite the opposite.

 

In Poland, to obtain a building permit, you must submit three volumes of documents, each usually over 100 pages long, and the wait for a decision often exceeds a year.

 

In this situation, I have no other ideas for this roof; I don't think I can simply build this house.

 

I tried to combine several hipped roofs in Revit to reduce the final ridge height, but I don't know how to combine them properly, I don't even know if it's possible to combine such roofs with a rectangular shape.

Edited 3 hours ago by MrtnBuilder

[JiAngelo]

Standard 7/12 hip trusses without their piggy backs above 9000mm would give you the look.  Instead of piggybacks you could install tapered plywood at the 10 degrees.

 

Its actually called a widows walk and the railing is decorative, not required unless there is rooftop access to the flat area from within.

[MrtnBuilder]

1 minute ago, JiAngelo said:

Standardowe kratownice biodrowe 7/12 bez łączników powyżej 9000 mm dałyby taki efekt. Zamiast łączników można by zamontować sklejkę stożkową pod kątem 10 stopni.

 

Właściwie nazywa się to wdowim chodnikiem, a balustrada ma charakter dekoracyjny i nie jest wymagana, chyba że istnieje dostęp do płaskiej części dachu od wewnątrz.

 

We don't need access to the roof from the inside. I'm more interested in whether it's possible to combine it with a hipped roof and how to do it correctly without sacrificing the height of the rooms underneath.

In Poland, flat roofs are among the more expensive roofs due to the lack of knowledge and fear of installing this solution.

But in my situation, where the maximum building height is fixed, this is probably the only possible solution?

[JiAngelo]

I didn't say you did.  I was saying the rails are decorative and not required unless there is access there.

 

Here's your trusses with a 2 degree flat peak.

This is hipped with a girder (circled in green.)  Flat top trusses start further back and above the garage trusses.

Below is gable ends, 7/12 front to back main house and 7/12 left to right over garage.  I think you could raise the front pitch maybe 5 degrees and not impact the flat roof?

 

Every number you've requested is represented in the story pole below and I'm under 950cm (500mm)

 

I can't believe this doesn't put a smile on your face.

[MrtnBuilder]

37 minutes ago, JiAngelo said:

Nie powiedziałem, że tak. Mówiłem, że szyny są dekoracyjne i niepotrzebne, chyba że jest tam dostęp.

 

Oto kratownica z płaskim szczytem o nachyleniu 2 stopni.

Jest ona zwieńczona belką (zaznaczoną na zielono). Płaskie kratownice górne zaczynają się dalej z tyłu, nad kratownicami garażu.

Poniżej widać szczyty, 7/12 od frontu do tyłu głównego domu i 7/12 od lewej do prawej nad garażem. Myślę, że można by podnieść nachylenie dachu z przodu o jakieś 5 stopni, nie naruszając płaskiego dachu?

 

Każda liczba, o którą prosiłeś, jest przedstawiona w poniższym słupku historii, a mój wzrost wynosi mniej niż 950 cm (500 mm)

 

Nie wierzę, że to nie wywołuje uśmiechu na Twojej twarzy.

 

I had no idea something like this existed. I wonder if they manufacture it in Poland and if anyone builds roofs on such trusses.

I've contacted several companies in Poland, but no one has presented me with such a solution.

Regarding the flat top of these trusses, how is it treated to prevent water from getting in? However, it's a part with a smaller slope, so it probably requires special solutions.

I don't know how the office will react. In this case, wouldn't they consider the roof to be without an angle or not sloping?

I don't know if they'll consider the roof to be flat on less than 50% of the total surface area.

Edited 2 hours ago by MrtnBuilder

[JiAngelo]

I can't speak to shipping with a the 2% sloped top chord, I'll ask our truss guys about this next week.

 

But we are currently doing a job now where we needed to stay under 35' and the truss company was building them with a flat top for piggyback trusses to be installed above.  They did this so that the trusses wouldn't be too tall, which requires extra expense to ship across our state.

 

We ended up changing the pitch from 10/12 to 9/12 and this allowed our piggybacks & shingles to fit under the 35' maximum.

But, we were prepared to install plywood flat over the top of the trusses, then add a tapered iso to give us the required 1/4" per foot minimum slope.  That equals 1.18 degrees, so 2 degrees is definitely above the minimum. here's an example of the tapered iso.

Here's a flat roof transition to sloped roof detail.  Ignore the gravel, a flat rubber roof doesn't need it.  The 2 degree slope will have water running off onto the shingles all the way around.

 

 

The good thing is this design has you 35.9cm under the authority's 950cm - in case they change their definition of ground level at the entrance. 

 

With the flat roof, I'd prefer the gable design so that I could install gable vents on the ends rather than hat vents on the 7/12 slopes or anything piercing the flat roof itself.

 

Hope this helps.

Edited 1 hour ago by JiAngelo
typos

[MrtnBuilder]

6 minutes ago, JiAngelo said:

Nie mogę nic powiedzieć na temat wysyłki w przypadku górnego pasa o nachyleniu 2%. Zapytam naszego fachowca od kratownic o to w przyszłym tygodniu.

 

Ale obecnie wykonujemy zlecenie, w którym musieliśmy zmieścić się poniżej 35 stóp (ok. 10,7 m), a firma produkująca kratownice budowała je z płaskim wierzchołkiem, na którym montowano kratownice piggyback. Zrobili to, aby kratownice nie były zbyt wysokie, co wiązałoby się z dodatkowymi kosztami transportu przez cały stan.

 

Ostatecznie zmieniliśmy nachylenie z 10/12 na 9/12, co pozwoliło na dopasowanie dachu piggyback i gontów do maksymalnej wysokości 35 stóp.

Byliśmy jednak gotowi ułożyć sklejkę płasko na kratownicach, a następnie dodać stożkowy profil ISO, aby uzyskać wymagane minimalne nachylenie 1/4 cala na stopę. To odpowiada 1,18 stopnia, więc 2 stopnie to zdecydowanie powyżej minimum. Oto przykład stożkowego profilu ISO.

Oto przejście dachu płaskiego w dach skośny. Zignoruj żwir, płaski dach z gumy go nie potrzebuje. Nachylenie 2 stopni sprawi, że woda będzie spływać po gontach dookoła.

 

 

Dobrą rzeczą jest to, że ten projekt umieszcza cię 35,9 cm poniżej 950 cm, które określa urząd - na wypadek gdyby zmienili definicję poziomu gruntu przy wejściu. 

 

 

Thank you. Maybe we can do something about it to build this building. Tomorrow I'll call a few companies and ask if they produce or know if it's possible to order such trusses anywhere in Poland.

Thank you again for your help; I was losing hope that anything could be done about the height of the building

[glennw]

Trusses should be easily fabricated on site with the correct hardware (nail plates, bolts, etc), timber, etc.,

designed by an engineer.