Building attached garage with different roof and ceiling specs??


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Hello all,


I am using Home Designer Suite 2014 and have just completed my first design for my planned cape cod home and love it (yay!), but have now moved on to completing the attached 2 story garage with bonus room above and am running into some trouble.


The garage sits directly adjacent to the house and shares the same back wall, with a depth that is a few feet less than that of the house (see attached image). The house has a 12"x12" pitch on the front roof plane that starts at the floor of the second story, and a 3"x12" pitch on the rear roof plane that starts at the 8 ft (finished) ceiling of the second story (so the back is fully dormered...see image).


Although the garage will have a gable roof and fully dormered back just like the house, it will need to have 7' (finished) ceilings due to height restrictions, and its rear roof plane will need to have a different pitch than that of the house. I would actually like to have the garage's rear roof plane start one foot below the finished second story ceiling height (so at 6') and rise at a pitch of 2"x12" to meet the front roof plane, which rises from the floor of the second story at a 12"x12" pitch (just like the front roof plane on the house). Then we plan to use the dormer tool to simply drop a large gable dormer on the front of the house. Our goal is to work with our height restrictions to still maximize our bonus room space above the garage. 


I was able to build the garage (for the most part) as a separate file, but when I try to add it to my existing home plan, I can't seem to build it's roof separately without messing up the roof on the home. 


The other garage problem I'm running into--even in the separate plan--is getting the plan to start the rear roof plane at one foot below the second story ceiling. I just can't figure out how to do it. I know it has something to do with the wall and room specifications, but can't figure out what. 


Sorry if this is a confusing post--will do my best to include as many helpful images as possible..let me know if you need others. Hoping the pros on here will be able to offer some insight. Thanks in advance!











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HI S.  a 2/12 pitch is pretty low , too low for Shingles ,so you'll need to use Roll Roofing in the same colour their


you are going to run into a few issues without the Manual roof tools of Pro  ( maybe Arch.HD too?) but there are a number of work arounds ( and some excellent out of the box thinkers here)and it looks like you are doing pretty well so far


usually you would set the garage second storey ceiling to 6' (72")  and then auto build the roof , then turn off the Autobuild Roofs and reset the ceiling height on the second floor to the normal 96" (84" in this case) ,try it on your separate plan 1st so you know how it works ,this process may mess up the house roof though as in Suite you need to turn auto roofs back on to get the garage to build, so all your settings there need to be spot on too and perhaps that roof complete with you new large dormer as it maybe not that simple to just drop on after.


not sure if you have seen these




might help to post your .Plan file too so anyone who can help can look at your settings etc and offer better help.



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I am confused! So this is just a guess.


Draw a wall down the center of the bonus room parallel to the ridge, about the center of the room.


Set the back room to have a ceiling height of 6'.


Build roofs. Turn off auto rebuild roofs if it is on. Delete the wall.

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I use metric so cannot help you with the roof. However I have noticed a few building issues. First congratulations you have done a great job.


You need to work out your rafter or truss spacing before positioning dormers. The dormers are also too close to the walls. The builder will have some issues with building these dormers. Your framing manufacturer will need an excellent Diagram to get these design angles right on the top floor and the attic area. You have not stated if you are having a crafted roof/ceiling with rafters or scissor trusses built. Also it is important to know the roof material first so you can design the spacing. Every roof has a different number of trusses or rafters depending on the weight of the roofing material.


 Your dormer ridges need a slight adjustment.


 However if you are just doing an outline of your wishes to hand over to an Architect or a draftsman what you have done already will give them a great plan to work with. and you could tell them what you are hoping for on the garage roof.


Have a look at the stairs though there are not enough stairs to reach the landing on the next floor.

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You have discovered the pitfalls of needing to rebuild a roof after you have made changes to a lot of your settings.


You need to do a lot of backstepping on the 2nd story main house floor.

You don't need to delete all the interior walls, but you DO need to drag them all back from making any room connections.

The whole floor needs to select as ONE room.  THEN draw the invisible wall that has been suggested.  The room created south of the invisible wall, should be set to 0 finished ceiling height.  The room to the north of the invisible wall should be set to the finished ceiling height of 8 feet.


Try rebuilding the roof to see if it behaves.

If all is good, then move into the garage bonus room.  Draw the invisible wall there also, and set the south room ceiling to 0",  and set the north room ceiling height to 6 feet.  Work with your roof pitches until you get what you want.


When the entire roof is correct (and ONLY when it is correct), turn off 'auto build' roof. 

THEN you can raise the bonus room ceiling to 7 feet, and the 6' slope ceiling will remain at the back wall.

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