I have an existing roof on my house that is pitched and creates a cathedral type ceiling underneath. I am considering increasing the pitch of this roof, for ascthetic reasons mostly, but also to add insulation to the roof, which I don't thick is adequetly insulated. There is no attic space right now, so I cant' be sure of the insulation, although it gets hot in summer time. I want the final roof to be 12/12, and to do this, I would need to raise the ridge by about 2'. From the ridge, I would then run rafters down to the bottom of the roof fascia. Instead of raising each rafter up and causing a mess, I am considering building a structure over the exsiting roof, and then sheathing over. That way I don't disturb the ceiling. I was thinking of also doing this in phases, keeping the existing shingles on as a I go. What do you think?

So, you want to leave your existing roof intact and build a new roof on top. Then, use the new dead space between the 2 for insulation?

I think, the first question needs to be, how are you going to carry the load of the new roof structure and, can your existing roof/walls support their share of that load?

A couple of things to consider:

that amount of work on the existing roof deck is going to pop existing sheetrock fasteners, so plan on patching, retexturing and painting the ceiling anyway.

The new roof cavity space needs to be ventilated above the insulation.

A couple small pilot holes through the existing ceiling may be able to confirm the existing insulation thickness. Easy to patch.

If you frame over the existing sheathing, creating a new cavity above the existing roof deck, the local code may require fireblocking in the newly created cavity.

You could leave on the existing shingles, but doing so may conceal decayed framing if there has been previous water intrusion and some areas of the shingles would need to be removed to install the new framing.

Also, adding new framing over the existing, changes the structural loads - it adds weight to the walls, roof beam and foundations...or is the exiting framing trusses?

You would need a permit, and an engineer or architect in your local jurisdiction to run calcs and coordinate structural and waterproofing details and connections.

Don't do it; do it once and do it right. While you may (structurally) be able to get away with adding a second tier on top of the original roof its not the greatest idea. Granted, unlike where I live you probably don't need to account for snow/ice loading, but such building is still alot more load on the existing structure.

You also really don't want to hide any current structural problems or amplify any deficiencies.

At least in my area it is highly unlikely that you would ever get a permit to modify a structure in that way.

With all of the repair you would need to do after such extensive work just pulling the old roof off and installing a new one may be comparable in price. It'll certainly be worth more when you go to sell your house.

Well, I talked about it with a contractor friend. I was asking him mostly about the loads and if this is a doable project considering the added weight. He said that sheathing over an existing roof is a common practice, mostly they remove the old shingles, and put new sheathing down on top of the old sheathing. Saves time and money. The only difference here is that I would be building a small truss on top and then sheathing over that. I mean I could pull up the existing sheathing, and build the trusses to the existing rafters, and then I would only have the weight of one layer of sheathing. So then the only real added weight would be the new pitched up rafters.

I'm sure that this may be doable and has been done before sucsessfully, but you should have a design professional give their input to make sure that it meets local building code.

Do yourself a favor and involve a Structural Engineer. There are lots of variables in the design of building systems that need to be considered; wind loads, snow loads, seismic considerations, etc., depending on what part of the country you live.

Have the existing structure evaluated and the new roofing system designed. This will also save your builder a lot of greif, as he will have a design to build to rather than making it up as he goes along. Believe me, this will be money well spent. I preach this to clients constantly, as I am a Civil Engineer. I have been dragged into numerous projects during construction to "fix" a problem that arose during construction. Believe me, this gets real expensive and causes heartburn when a problem stops a construction project dead in it's tracks.

Wouldn't you sleep a little better knowing that your roof has been properly designed? The Engineer may also be able to give you pointers that can actually save you money during construction.

Speaking from personal experience, it typically is much more cost effective to have building projects properly designed the first time. Projects become alot more expensive the second time when the work has to be redone.

Better check local buillding codes. Around here that would not be allowed. Fire codes wouldn't allow a roof over a roof. It traps smoke and fire causing danerous conditions for fireman.

You may be able to tear off 4' at a time and add a room and attic type truss. This will give you the added pitch your looking for (12/12) and a bonus room with a second floor.

The fact that you now have a cathedral type ceiling now doesn't mean you can add a second one over it. There is a lot of stress pushing out on the tops of the walls with this type of construction. Adding weight just increases the amount of force pushing out on the tops of the walls. This could cause a collapse. I've personally seen it.

Also depending on the type of weather you have, if venting is not proper condensation will rot the roof deck and ridge beam, seen that one also.

As an insurance adjuster... this type of claim may not be covered.

So its an open beam ceiling right? Very nice to live with inside but they are notoriously inefficient when it comes to heat and cold infiltration.

I would consider two options before you attack the structure, because once you cut into it you will be seriously opening your wallet.


1. Consider reroofing using an insulating "styrofoam" panel system under your roof sheathing. Its designed for use in roof systems that have no air space. Air space between your roof and ceiling acts as a buffer zone by the way, which is why homes in your area usually have nice attic spaces. Also consider switching to a very light colored roof...... like white. It will seem like Xmas all year but your heat performance will double.

Other factors that can help keep your structure cool are light exterior walls, good glazing with tint or Low E, and climbing vines on trellis panels on your south facing walls. A vine can decrease wall temps by 10 degrees.

2. If you have an already high ceiling build down into the space and install cosmetic beams to retain the effect and put your insulation above. Thats not as easy and proper appearance would be dependent on your plate height as well.


Raising the roof is good in dance clubs, but hell in reality. Prepare for planning hell as well. They will not want to approve it, which means you will NEED and engineer.



cheers,



oh, i almost forgot. You could build a Parasol roof system to shade your existing structure.

existing roof (3 tab, etc) tear off is an equal weight trade when replaced with a like product. look into poly-iso panels. light weight, high r value. they fasten w/long screws then resheath. spread out over the entire roof, the sheathing shouldn't add a high load. prob less than a reshingle over an exsiting roof. see if continous ridge venting will provide the air flow you need. you have to make an ajustment at the facia boards due to the added thickness.

What is the typical procedure? I would have to submit for a building permit, with plans, etc. If approved, can I then hire my own crew to do the work, or do you have to have a "licensed" contractor? Finally, is a post-alteration inspection required?

Typically you need to get plans and then submit for the building permit. At least around here it doesn't matter who does the actual construction as long as they stick to the plans. You will probably need to have it inspected afterwards to get your certificate of occupancy, but thats probably more up to your locality.

Everyplace is different so check with your local inspector. Most places now require a design plan based on the building codes. This would show current construction and purposed changes with inspections based on what your area requires.

Thomas

Do a search on your City regulations on line. Many city & towns have fairly decent web sites. This is where I always start when looking at new job in a town that I never worked in before.

Check out the San Antonio website at

http://www.sanantonio.gov/dsd/residential.asp

Seems like a real user friendly site with alot of good information. The FAQ section should answer most of your questions.

It can be intimidating talking with building department. Many times these guys aren't too friendly. Often people are taken back by this attitude, but these guys have to enforce the Code requirements & typically fight with contractors/homeowners; the constant conflicts kind of turns them crusty. Typically they have no tolerance for the rooky questions. I am used to dealing with folks up here in the Northeast, the attitude may be different down in Texas. DO NOT go in there with a "I pay your salary" attitude; they will remember you & go out of their way to bust your balls!!!

Start doing your research online; you get to browse thru regulations while sitting at the house in your PJs drinking coffee. Try & educate yourself on the process before meeting with the guys at the building department. It will make things less stresfull for you. Go in with a little knowledge, ask them if they could help to clarify questions you have & try and make friends with these guys. Like anything else, if you seem like a cool guy (many times the exception at their counter) they probably will be very helpful to you.

Many towns will allow the homeowner to self perform building projects but not electrical or plumbing.

Good luck with your project.

be careful to investigate the fire code.
In MA, when you pull a permit to add or change the primary dwelling, you now get the pleasure of upgrading your entire house to the new fire code for alarms.

Rich

I had a similar situation. I have a cathedral ceiling, which had no isulation, and would get very hot in the summer. When it re-roofed the house, I removed the shingles, and got down to the bare roof decking, then added 3" foam insulation, and then new decking on top of the foam. I also added a radiant barrier on top of the foam. Granted it doesnt work as well without an airspace under it, but still provides some benefit. Adding radiant barrier, and a light colored roof made a big difference in the house. Even in summer with 110 degree temps, the air conditioning usually doesnt come on until 3 or 4 in the afternoon.

if you go the the insulated panel route, ensure you use a closed cell product.

personal liability is a factor to consider when assembling a crew and acting as a 'private contractor'. someone takes a header off the roof, it could cost you dearly. even so much as a "i hurt my back" could become a nightmare. get bids from licenced and bonded contractors. ask for past customers and get feedback. a good contractor should be more than happy to provide this info. ask the usual ?. was the work completed in a timely fashion? was the yard a pig sty when the job was finished?

when we did our roof (2 layers of comp), the contractor showed up with a scissor lift bed truck for hauling away the waste. a tear off crew of 8 or so and it was stripped and papered in 1 day. next day, 2 roofers and the shingling was done in 2 days. after all was said and done there was not so much as a piece trash in the flower beds.

k

This is my plan, by the way, notice that also, with this pitch change, I can also join the porch gable with the main gable. The jackasses that built the house left a 2' gap between the two gables, so that the porch always gets wet!






I have been looking into this radiant barrier also, as a way of getting better insulation.

http://www.insulation4less.com/prodex_Ffmf.asp

I have also seen these sheathing boards with radiant foil already on them. They are relatively inexpensive, when compared to plywood. I wonder if it would be better to use the prodex insulation, or the sheathing with pre-attached foil? Anyone?

http://www.solarboardosb.com/

This is not really off topic.
This reflects what we do here a lot, Like buying a car with the thought of fixing it up a bit and then realize there is more invloved than previously thought.

At leat the car you can cut your losses and get rid of it. The house might be a BIGGER problem if it goes wrong.

Don't do it. You can put radiant sheathing on top of the existing sheathing once the shigles are removed.

You could also put 1" fur strips on top of the existing sheathing lining up with the rafters. Put your radiant sheathing on that and re-shingle. the air gap with ridge vent will carry a lot of heat out.

I am not an engineer so I suggest you get a hold of one before doing anything you will regret BIG TIME.

Well, it's mostly for asthetic reasons that I want to do this. The ability to add radiant shielding insulation is just an added bonus. Plus, there is the porch area problem I mentioned, and the front siding under the gable needs addressing as well. Basically, my house needs a lot of work, and I figure I might as well make it the way I want it in the process.

Are those 2x4’s that you are proposing for the new roof rafters? As I understand your drawing, the bracing are going to distribute loads onto the existing 2x8 roof rafters, essentially making some type of truss. In order to properly tie the truss system together, the existing sheathing will have to be removed to tie the added truss components into the existing rafters, as you show with the plates connecting the vertical bracing into the rafters. Additional bracing will be required to deal with horizontal loads; we’re not just dealing with vertical loads on a roofing system.

Honestly, this will not be as easy to piece together as you may think. Renovating an existing structure is typically much more expensive than replacement; it will all be time consuming custom work, and man-hours are expensive and add up quickly. I am sure that there are a few contractors on here that can back me up on this. The shingles, sheathing & existing insulation will need to be removed before you start building your trusses. You may find problems with the existing roof or wall structures caused either by age, insect or water damage that will need to be dealt with when encountered.

What will all of this demolition & renovation work do to the interior finish? Kinda hard to say. I would bet my car that the interior will not escape this type of major renovation unscathed and will need to be refinished, possibly replaced! As has been stated above, at a minimum you will have cracking & screws popping thru the sheetrock. Sheetrock won’t deal with all the banging too well. Most likely the sheetrock will be severely damaged by the demolition & construction (think of what happens as all those little screws start to pull thru the sheetrock; all the weight being held by that many fewer fasteners), it might even pull away & drop.

You might want to evaluate the cost of the custom renovation vs. removal of the roof and replacing it with new trusses. Complete demo of the roof would go quick, and new trusses can be lifted in place & set within a day or two. Performing select demolition while protecting the interior and fabricating the custom trusses on the roof will take quite a bit more time. Give it some serious thought.

With the field built/modified truss that you are proposing, I will guarantee that your city/town will require engineered calculations and a stamp on your plans to ensure that this system will actually work before they will issue you a building permit. A design professional will have to inspect the existing structure, design (or at a minimum, back up your design with calculations) & certify that the proposed roofing system will meet the building code. Talk with the town building department & ask them what will be required.

With the radiant barrier, it would be easier to buy the boards with it already on. I put radiant barrier foil on my house, and it was a pain. It seemed like every time I would roll it out, the wind would pick up and blow it everywhere. As soon as I put the last staple in, then wind would quit. I think mother nature was having fun at my expense.