I have a SIP home (2500sf ranch style, rectangular hip roof) I love the home and it works for me. I remember when I was looking into building 8-9 years ago that the SIP structures I seen advertised had the SIP building structure self supporting with some just having a large single beam across the center of a cable roof design. The main question is if they are all glued and screwed together.....why the need for added post / beam. I feel as if I could drive a train over my home looking at the size of the glu-lam beams the engineer put into it.

sled4fun,

SIPs are great at spanning over a space but its the connections at the panel ends that take a lot of stress when the SIP is loaded. Its the beams that alleviate the stress on SIP connection points. The OSB skins have only so much nail holding strength so it is unwise to over stress the material.

sledforfun;

as a general rule SIP buildings do not need a post & beam frame, most need a ridge beam, although on some small homes we have also eliminated that need as well. the larger the building the more support internally you will need possibly with more beams or bearing walls.
Very large spans in commercial structures would require a frame to go across large spaces

I understand what you guys are saying about wider spans and such. On my home the plan check from the county questioned the sips load bearing ability and made us increase the roof panel thickness and the type of connections used (no snow load). They look like silent floor beams between each panel. The home is about 35' X 78' hip roof and the beams they made us use are 18"x6" Glulams supported by 6"x6" uprights. I think that most inspectors are not educated enough on the loads that sips can take and demand that roof spans be built as if the sip has no structural support at all.

Posted By sled4fun on 22 Feb 2011 07:25 PM
. I think that most inspectors are not educated enough on the loads that sips can take and demand that roof spans be built as if the sip has no structural support at all.

This is common even with engineers, overdesigning is a cheap way for engineers to ensure extreme safety at your expense.

There is a way of not using a ridge beam with OSB Sips for a simple gable roof. It involves attaching 'collar ties' to lumber splines at each vertical panel joint (4 ft o.c.) about half way down the pitch to create a kind of 'A' shaped truss out of the panels/collar ties.

Your project does sound over designed. 6x18 beams at 4 ft on center between panels sounds excessive.

The Glulams beams are laid out in this type of configuration >------< across the center of rectangular shaped home with each end point going to each corner of the home. The splines are like a silent floor joist on 4' centers between each panel. Each roof panel is Insulspan 11" thick by 24' long and it is a 5/12 pitch.

Now that you gave a little more detail, it doesn't sound so overdesigned. Your roof panels with 'I joist' splines sound about right. You would have to give more detail about your beam spans and how they are supported within the plan to get a sense of their design. You should mention your location too because you say you don't have a snow load, but you may have a high wind load or a seismic load. I have a feeling your engineer designed it just right.

By the way, if your home is 35 feet wide and your roof pitch is 5 in 12 and your roof panels are 24 feet long, that means you have 5 foot overhangs on your roof, which is not common, but may also justify the roof panel thickness and spline choice.

Ok I looked at the Insulspan drawings. So much on relying on memory. The house is 42' x 68' (2' overhangs w/front & back porch) The Glulams are supported at each connection bucket 6x6 post and again about mid span of the main Glulam beam and at each corner via 6x6 post. The home has 9'sidewalls and I live just east of Sacramento, CA. 1300ft elevation and have gotten 4" total snow over a 7 year period.

sled4fun;

the problem isn't that it is overbuilt, it is built for an anticipation of a much greater snow load

Posted By cmkavala on 23 Feb 2011 05:32 PM
sled4fun;

the problem isn't that it is overbuilt, it is built for an anticipation of a much greater snow load

Maybe that is why the footings are so deep and wide too. My nephew said that he usually sees that massive of a footing on a two story home.

Sometimes the heaviness of a beam is partly because of seismic design. More meat at the connection point to resist movement.