# Question a flat roof versus trusses



## hermitfarmer (Jun 22, 2004)

Hey got a question The back end of my barn/house I am thinking since it is butted up to the front of the house I am thinking about going with a slanted type roof for the rear. The width is 30x30 so not sure if I can stretch it across with out any interior support. The rear of the building is going to be the kitchen with a lean to on each side to store equipment. I had thought that a couple of treated 4x4 that would rest on the cement floor in the kitchen could be used down the center to support the roof. 

I am also looking for any ideas on putting telephone pole type deerhutning shed at the back to offer better sighting for the bottoms near the creek to use as a covered area a 2 for 1 option and Since I am smack dab in the middle of 70 acres so no neighbors to complain about what it looks like.


----------



## shawnlee (Apr 13, 2010)

As a carpenter and not being able to envision exactly what you have.......

I can only offer this advice....

A flat roof of that size will have very little slope, unless you have one end very tall and the other side fairly low.....

I tend to shy away from anything less than a 4 on 12 pitch that can be shingled......leak issues and roof longevity etc.

Just visioning what you laid out in your post and the use of one beam/support down the center and not knowing your snow load in the area...I would guess it would have to be at least 2 by 10s to span that distance.....basically 16 footers on a beam or joist hangers...preferably 2 by 12s at that span to ward off sagging over time and provide for ventalation and insulation...depending on climate..


I can evision the lumber costs coming real close to trusses at this point and 30 foot by 30 foot open is a fairly large distance without some dividing walls and would be cheaper to do a beam or 2 inside on the truss costs.


You could also stick build the trusses with one beam down the center, but would be more labor intensive this way.......


At this size and what you have planned a alternative is to go completely flat and do a proper flat roof type roofing material on it.....which is more exspensive and more critical that it is done properly so it does not leak.

If I had a better picture of what you have and what you have in mind, I could could give you better, more specific ideas of which would be more structural and cheaper and which way would be ideal and what you can actually do as far as options.......

From what I am understanding you are going to have a 30 by 30 kitchen of open space..?

Or is this 30 foot taking into consideration the proposed lean 2 on each side.....which is a totally different approach than I mentioned above......

Some pictures or even some understandable sketches with side veiws and top views would help everyone alot to give you better answers.


----------



## HermitJohn (May 10, 2002)

Flat roofs are a pain unless you live in a desert area. You save a little in initial material costs, but then have to live with PITA leak problems forever. 

If I were going to build flat roof, would used I-beam wood trusses rather than dimensional lumber to frame it. Those I-beam trusses are quite amazing in their strength and spanning ability and lighter weight than solid dimensional lumber.


----------



## RonM (Jan 6, 2008)

Remember, the steeper the roof the longer it will last..


----------



## Wylie Kyote (Dec 1, 2009)

A rule of thumb is, the flatter the roof, the deeper the ribs on the metal sheeting. As an old roofer I would not go with anything less than a 12 degree pitch.

Wylie


----------



## texican (Oct 4, 2003)

Flat roof and a couple inches of snow = epic roof failure. Our local constable built a dreamy little house w/attached horse barn. First snow came along crushed the backside of his barn.... he didn't calculate for the rare snow loading...


----------



## hermitfarmer (Jun 22, 2004)

Thanks what I had thought of was a slanted roof high in the front and slowy tappering off at the back like some older roof styles for out buildings. A flat roof never works you are right. I have the rest of the structure laid out like an old timey house om peirs so that air can flow under the house. My plan was to build the rest of the house later when I can get the money. I just paid off the front part of my land and I have just enough to do the roof or I can wait and build it with regular trusses. I have no problem with treated timbers 4x4 or 6x6 but with a trus system I can have the added advantage of a high roof and it helps in the south for that hot air to get as high as it can. 

As a thought to anyone building I have a small place that has the same type roof in the winter I made a channel that I put up 1/4 inch insulation to cover up the high truss area to keep my heating cost down some and take the 4x8 insilation sheets down in the summer. I wanted a slanted or shed type roof to use this as a midfied living space for myself. My plans were to lay out the lubing shower and sinks and then pour the floor in concrette. After that I wanted to use the cedar i have cut to run through a planer and finnish the walls. My thoughts I hope this lays it out better for you. The roof I have some new green metal roofing for the roof and I am not sure of the slope of the roof but it can be high in the front so I can slope it enough so I can have the sheds on each side and it will help with heat in the summer.


----------

