Double Wide Rebuild

[Howkeh]

I am please to have found this site. Lots of people with lots of knowledge. Please ignore the flag, I thought I would just pick a weird one. I live in Quebec. Anyhow...

I am thinking about purchasing a double wide (built in 2002) that has a mold problem. At least it had it before it was abandoned two years ago and before they tried to do some abatement. Two superficial visual inspections do not show much mold problems. Much of the inside is stripped, some walls are bare to the studs, carpet has been removed, most counters and appliances are gone, frost has burst one toilet tank, the roof is leaking around skylights and vent, etc. To be on the safe side and (more importantly) to increase cold weather efficiency, I am planning to rebuild almost the whole inside of the building.

1) I was planning to rebuild the whole inside envelope by adding a second 4" wall with offset studs to the inside of the exterior walls. I would add a new vapor barrier on the inside of all exterior walls and effectively (at least theoretically) seal out any remaining mold and add a significant amount of insulation. My goal is "super insulation". Is this approach practical? Or should I insulate from the outside? I am concerned about having to move bathroom and kitchen drain holes and electrical outlets, but much of the inside is damaged anyways and I don't mind the loss of living space. I want to add a few windows on the South side though, so exterior work may need to happen also. Opinions?

2) To super insulate I need to worry about the ceiling even more than the walls. Insulating on the inside of the ceiling does not make much sense to me since it will lower the ceiling and does not address the leaking roof issue. I really would like to eliminate roof vents and skylights. It seems to be troublesome to have that many openings in a roof. I am thinking of stripping the roof, change what is needed and add an insulated roof-over with a metal roof or something other less eco-sinful than asphalt shingles. I would like to add over-hangs and eaves. Has anyone done something like this lately? Opinions? Construction ideas?

Does this whole project make sense at all? I don't mind the work and hate to throw away things, but I am worried that rebuilding a mobile home (where everything seems to be glued in place) is more trouble/costly than building from scratch.

Thanks.

[JD]

Hi and welcome to the forum.

First I would recommend hiring a licensed mold remediation crew to deal with the mold problem and require a certificate when they are done. From what you wrote, the mold is still there whether you can see it or not. Mold spore roots penetrate deep into porous surfaces like wood, sheetrock, paneling, etc. Bleach will not kill these roots/spores. The work needs to be done properly with testing on type of mold, hepa filter - zero pressure air control, total removal of some surfaces and proper treatment of the rest.

Once the mold issue is handled, I would not use a double vapor barrier as this will be begging for another mold problem. With the mold removed, you could double the wall thickness and treat the wall as a single cavity. Vapor barrier should go on the warm side of the wall, depending on your area's average weather. If you were to add a second 2x4 wall, you could stagger the studs so they don't line up with each other. This is an excellent soundproofing method used in music studios and live sound rooms. I would also block under the subfloor for the added wall. Both walls can be insulated with standard batt insulation.

An insulated metal roof is an excellent way to insulated the ceiling. If you were replacing the ceilings, replacing the existing insulation with better insulation would also be good. Probably cost prohibitive if you weren't already replacing the ceiling. If you remove roof ventilation vents, you may want to add powered gable vents to the wall to make up for that ventilation. Depending on you climate zone, you may still need a vent on the roof to assist the powered vent.

JMO
JD

[Howkeh]

Well, thank you for the quick and informative response.

I am told that some abatement has occurred regarding the mold, but the seller is covering his/her rear end by saying that "the entire extend of the issue is not known". I have not been able to get any official documentation. They did quite some "looking" around in the walls and such. A former occupant told me that the issue ion his opinion has originated in the wall at the laundry machine but I cannot see any water damage in the walls there.

I was not planning to use a double vapor barrier, but as you said, only one on the warm side. I will strip the walls of their paneling. They are usually glued, right?

To block under the sub floor I have to remove the insulation under the floors, correct?

Are there any construction drawings anywhere available for those who can do it themselves (or think they can) to construct a light weight roof-over (2x4 or 2x6 rafters) over the existing roof? I am sure the ceiling is insulated (home was built in 2002) but I want to heat my new home with the sun and a candle. OK, a large candle.

The roof vents should probably stay. Air needs to flow. I meant to say, I would like to re-route bathroom and kitchen vents as well as skylights that penetrate the roof.

Questions, questions. I am sure to be here often if I buy this thing.

Thanks.

[Greg]

Hi & welcome. The home is new enough that you might get lucky if you contact the manufacturer and get the build prints.

It sounds like the seller is trying to place all & any costs associated with the mold. Depending on the price it could be a deal or a money pit. Depending on your ability and how much you want to risk, you may want to have an inspection doneby a Mold company. Greg

[JD]

I agree with Greg and you that the owner is trying to cover his butt. I am not sure that would fly in most states though. If a building, apt or mobile home is sold as habitable, then there would not be a mold issue.

I find that it is the exterior wall panels that are glued and not the interior wall panels. Probably to help keep the walls from racking. Not all homes I have worked on have these walls glued. Yes, to block under the new wall, you would want to go through the bottom, unless you were repairing that floor, in which case you can block from the top. I would say that the blocking is optional, as you should be right next to double rim joists.

Personally, would not recommend a wood framed roof-over installed onto the home. All homes roof loads are built close to the specs of their climate zones. ie. 20LB, 30LB, 40LB, roof load or snow load. Adding framing, sheathing and a roof would certainly push a roof over this load limit. I have seen them done successfully, but most times I find bowed ceilings and floors. This is just my opinion. I am sure others would disagree. The metal roof Mark shows in his Mobile Home Repair Manual would allow you to add polyiso foam panels between the existing roof and new roof panels.

JD

[Howkeh]

Yeah, the building blue prints. Sure would like to have them, and I called the manufacturer, but...

The serial number is supposed to be on the walls of the master bedroom. It took us a while to figure out where this might be. It turns out that it was a walk-in closet and the walls have been removed in that area. So, no serial number at the moment.

About the roof, I figure there is an air space above the blown-in insulation. Would an insulated roof-over on top of the existing roof actually do anything if that air space is still there? I mean, what is the point of insulating a layer of fresh air, no matter how thin it is? Would I not have to fill that space first?

Also, when I remove the shingles I remove a lot of weight. If I add a metal roof (plus framing, and sheathing) will I add this much more?

BTW, can one walk on modern metal roofs without causing damage?

Yes, I am planning to be right next to the current interior walls. I guess I will look to see if blocking is necessary.

I will ask if this building is considered save for occupation right now.

Thanks!

[Greg S]

In my opinion the feasibility of what you are asking depends entirely on how cheap you can purchase the home. Do you know the value of a similar double wide in your area. If so I would be looking at paying maximum 50% and reduce that by the estimated repair costs. Repair costs should only include necessary work to bring the home back to what it was not the additional work you intend to improve the home. You should probably only pay about 30% of ARV.
Question: Are you planing on residing the home. As you have mentioned new windows etc, if residing I would add additional insulation on the outside. This would be more cost efficient and a lot less work than adding all new interior walls and additional insulation.

[Howkeh]

The town considers the building inhabitable. At least it is not condemned. And I have the serial number now.

I hope to purchase the home and land for much less than it was worth just a few years ago. As a matter of fact, I will put an offer in based on the value of the land alone minus the costs it would take to remove the mobile home (which I do not want to do). I might get a good deal but still don't have a home to live in.

If I insulate on the outside (which makes a lot of sense to me) I will run into trouble with the short roof overhang and I have to rip out the inside anyways in several places to address the mold issue. And I do want to change the layout. I will have to prioritize. Don't we always.

At this point it is all about the roof. If I can add insulation without too much trouble it makes sense to look into adding more insulation to the walls as well. No sense in adding more to the walls if the roof stays the same. If I can add overhang I can insulate the exterior rather than the interior.

I still am not sure how to add insulation to this sort of roof. It is apparently blown in mineral wool. 4" rafters, 16 on center. Asphalt shingles. No vapor barrier (at least that is what the manufacturer said yesterday o the phone.). Currently the roof is R30. I would like R50. How???? Complete rebuild?

Luckily I get most of the labor for free and shortening my commute to work by 110 minutes per day gives me almost 9 working weeks additional time. That will help.

Thanks.

[JD]

2" thick polyiso foam panels will give you about R16 that you would be adding to what you currently have. This can go under the metal panel roof that Mark describes in his Repair Manual. Personally, I would not go more than 2" thick on the foam panel. Even that is a lot when installing the fasteners to the roof. There is just too much soft area between the 1x4 lath strip and the metal. But polyiso is very stout and should make a good base for your roof. It is used for this purpose all the time. Mark's book also shows how to make an overhang to your home when installing these roofs.

The polyiso board is pretty expensive, maybe $1/SF. a 24x60 is ~$1440 worth of foam board. Styrofoam board is a little cheaper at about 70 cents a foot, but it is about half the R factor and not nearly as strong.

JD

[Howkeh]

R16 is good. But what do you do with the current air space above the blown in insulation and the fresh air that flows there? To add insulation outside air has to be stopped from flowing between layers of insulation, right?

What is this book you are talking about?

Thanks! Good info.

[JD]

This space would require the same venting as it would without the insulation. Now I don't have experience with this kind of roof in very cold or humid climates. I install foam insulated roofs here in Fresno, where we have mild winters and mostly low humidity. So I don't know for sure what this type of roof would be like there. But I would think that the roof should be vented with actual vents and some sort of plan. The permeability of the building materials should be considered in the plan, but not the direct method of venting.

JMO
JD

[Howkeh]

Yes, I agree some sort of ventilation seems proper. Fro ma scientific principle point of view, I just cannot figure out the benefits of adding insulation above a vented air space. It is like being out in below freezing weather with a jacket that lets wind get in. I have one like that and I sure notice the cooling effect even though the jacket is mighty warm if I keep the air from flowing through.

I can see that adding insulated panels will decrease heat gain since the hot roof will not radiate hot air into the interior. But heat loss?

How about a self-supported roof-over? You know, 4x4 posts that carry the whole second roof and rest on the same slab.

Thanks