More attic framing questions (with pictures)

As mentioned in other threads, I’m in the planning stages for renovating a walk-up attic.

The current situation:

Front-gabled roof, about 25 feet wide, and 45 feet long.
It’s a little over 11 feet in height to the top of the underside of the roof
The house was built in 1915, and has a slate roof
The current attic framing has 2x6 roof rafters, about 20" apart
There are 1X6 collar ties about 7’ off the floor, also every 20"
The floor joists/ceiling joists are 2X7", about 22" apart

The plan:

In the middle half of the roof, the plan is to pop out a 21’ shed dormer on one side. We would also put in 5’ knee walls on the portions that do not have the dormer. So, on the left side (non-dormer side), we’ll have 5’ knee walls running “North-South”. On the right side (dormer side), we’ll have 5’ knee walls for the first 12’, then the dormer, and then 5’ knee walls for the last 12’.

Here are some pictures:





Here are some of the questions I’m thinking about:

  1. Insulation issues aside, do I need to sistering the roof rafters for structural reasons? I will be hanging new ceiling joists from the roof rafters, which will also have drywall, insulation, etc. So, that is a lot of extra weight. Some of that extra weight will be transferred to the floor through the North-South walls, but a lot won’t be.

If I do need to sister them, what is necessary?

  1. I have floor joists that are 2" x 7", and are 22" apart and run ‘East-West’. They are about 25 feet wide, with a center line of support down the middle of the house running ‘North-South’. Are those going to be adequate? The plan was to cover the floor joists with 3/4" T&G.

  2. What I do I need for ceiling joists/collar ties? I currently have 1X6’s, which will be removed. In the two rooms without a dormer, they will span about 8’. If I put them on the rafters, they would be about 20" apart.


If you don’t get a structural engineer or architect involved with this, you are headed for a big fall.

Why are you asking such detailed an specific questions on a home inspectors board? You are asling for professional advice from people who are not qualified to design and spec your project. We can inspect it, once it is built, but we cannot help you build it.

Pay the money and have it done right!

I know that you are just trying to save money (always a good idea), but there is saving money and there is just being silly.

Get a local, professional, licensed and insured professional to help you.

Sure, it will cost you, but the job will be done right. You can pay up front or you can pay afterwards. But you WILL pay!

And it it turns out that the pro messes up, they will have insurance and you will get it made right.

Do not be penny wise and pound foolish!

I have made the same mistake. It ain’t pretty!

I don’t mean to slam you, just giving you my best professional advice.

Hope this helps;

The questions you are asking are the exact reasons why you or your builder must pull a permit.

The municipal requires builders to submit a plan (blueprint) with all the details you are asking about, before they issue you a permit to build.

Do you plan on pulling a permit?

Both Will and Dave make very valid points.

As a contractor specialising in this type of work I recommend you hire a qualified contractor familiar with this kind of work. The floor will definitely have to be re-framed to carry a live load, if you are adding a full dormer, knee walls, ETC, more than likely I would recommend a complete tear off of the roof, re-frame the floor with TJIs, this will transfer the weight to the outside wall, roof trusses, to lighten the load and conventional framing/insulation from there.

This is just my opinion without seeing it but I have ripped enough roofs off houses to know it’s better than trying to piece meal everything together, IE blending new construction to the old and meet code and then most of all you need to make sure in the end you have added value to the home and not taken it away.

Hope this helps.

The job will have a licensed, insured contractor and a building permit (they are very strict in my town with the inspections).

I posted some questions here as there seem to be a number of pretty well-informed people who have been thoughtful enough to answer some of my other questions, and I like to hear the opinions of people who:

  1. Aren’t trying to sell me something I don’t necessarily need
  2. Aren’t trying to get out of doing work

I’d like to get a feeling for what I should do, and make sure that I get all of that written out in the specs for the contract. I don’t want to bid the job out, and then have someone come back and tell me “I didn’t include beefing up the floor framing in my quote” and have a surprise bill.

I am sorry for misunderstanding you, Nathan.

Send me the specs (e-mail below) and I will do my best to help.

Hope this helps;

What other information do you need to know?

If you live in the US the IRC 2006 code book along with any city/town exception will dictate what you can do. If you look at the load chart for a live load it tells you what the minimum spans are based on what type of framing material you are using.

I’m getting the impression you didn’t like my reply as you have not commented it.

I think that would be cost prohibitive for me, and none of the contractors that have looked at it have suggested that. There’s always the “best way” to do things, but there’s also usually a “pretty good” way that costs half as much. I love watching This Old House, and the care and detail (and expense) that they put into all their projects. But we all can’t afford to live in million dollar homes.

Nathan, I understand all to well about costs and I’m not there to see what you have for a house.

One other thing that has to be considered is this, you said you plan to put a dormer on, I assume it will be on the back? Typically what happens in an old home is when you stand your wall up to make up the dormer and to meet code it usually means that when you try to tie into the old roof your new roof will end up be flat, this is why I said you want to add value not take away.

Again, these are all issues that I deal with on a regular basis, sometimes it works sometimes it doesn’t and I’m not there to see what you have. Some exterior shots of the house would be great.

Nathan, I just re-read your original post and you say the roof is 11 feet high. If you remove 21 feet of that roof for a shed dormer here are some numbers I came up with.
92 5/8 for wall studs
6" for top and bottom plates
9 1/4 for rafters
This gives you a total of of almost 9 feet to the top of the rafter which on a 25 foot wide house will give you a slight pitch to the roof.

Again, I don’t know where you live but in my area snow loads would be another factor but I do think it could work, just not sure how you would tie the new roof into the old one.

Keep us posted, this is interesting and I would like to keep the communication going, especially throughout the project.

Like Peter ,I am a contractor who would like to give my .02 cents.
If I were you I would put the project on hold until you can afford an architect.I believe you are about to get into a "pay now or pay later situation.

An architect will answer all the questions your potentail contractors do not seem to be able to.Thus giving you peace of mind.Jobs have a way of becoming more expensive if you fly by the seat of your pants and don’t get the details you need in the beginning.

Frankly ,I’m already worried about your contractors if they think 2 X 7’s @ 22" o.c. spanning 12’-6" will be sufficient and then adding a dormer to that is asking for trouble.

It would be a shame if you could not finish your project due to running out of money because of unforseen problems that an architect could have answered.You don’t have to be a millionare,I suspect most of us are not,but you may wish you were if you don’t get started on the right foot.

Good Luck to you.

I agree with you to a point, if a contractor who has years of experience with this kind of work can design a remodel that meets or exceeds code and is approved by the building inspector, you will be OK.

I design all of my remodels which have never been rejected by code enforcement.
You do make many valid points such as how to tie the new and old roof together, load points, ETC.

Check out the pictures below of my projects, also I am designing a 27X55 ranch conversion into a colonial, I hope I get the job but the first round budget has come in at 160K, a little pricey for the house and the neighborhood. Remember this, Price VS added value.

DSCN2516 (Small).JPG

DSCN2695 (Small).JPG

DSCN2683 (Small).JPG

DSCN2689 (Small).JPG

DSCN2435 (Small).JPG

Peter ,
I do the same.

Without going back through the previous post I think I recall that Nathan conveyed that none of his potential contractors were able to suggest or had drawn up any type of project plans.
That is why I suggested he cut to the chase and get an architect.

Nice looking projects you have there and good luck getting the next!

How much does Nathan think an architect will cost? A good architect can save many times what his fee would be, ensure that all bids received are for the same scope of work, and solve problems in advance, helping construction to go faster and easier, and be solidly on the side of the owner. That sounds like a bargain to me.

Just one “tear-out-and-redo” can cost more than the architect’s fee. And what value is lost by living with a situation that would have been done right if an architect were involved, but wasn’t? Someone else said wisely that you want to add value, not decrease it. Architects know how to do that.

Maybe an architect might ask something like $2000. That will not necessarily raise the cost of the job by $2000. It may well reduce the cost of the job by more than that. Nathan may be being penny-wise and pound-foolish here, and as someone else pointed out, he’s asking for advice from a source where most, while they may be excellent inspectors, are not qualified or licensed to give it.

This was proven time and time again during my many years of building.

Nathan, you would do well to work with experienced and qualifed professionals. :slight_smile:

The house is a front gabled house. The dormer is going to be on one side, in the middle of the roof. It would be a “shed” dormer, where the tie in would be at the apex of the roof.

The construction plan is to build the walls inside the attic, take the shingles off the roof, and then cut the roof on either side of the dormer, raise it up (essentially the top of the roof is like a hinge), and then rest the new roof on the pre-built walls.

In my area having an architect do what you are suggesting costs around 18% of the total project costs (I know because I asked a few of them to bid on the project), which in this case would mean an architect would cost $15,000 - $18,000. Too rich for my blood.

Just to clarify, I’m not goingi to take the advice I get from an internet message board and run upstairs and cut the roof off my house by myself. I merely am taking the opportunity to kick around some ideas with people who might like to talk about this kind of stuff for fun. As I mentioned elsewhere, the project will have a licensed and insured general contractor, a building permit, and numerous inspections.

Never going to happen, you really need to re-think what your doing!!!