Assistance with Self-Build Home (yes I know.... but please at least read the post) 1

[Beenjammin]

Greetings all,

Before I post, a little about me. I am an electrical engineer and I have worked in the field (doing real work in the past). I have worked and built things most of my life including designing and building from scratch kitchen cabinets, extensive remodeling projects (think removing interior and exterior walls repositioning headers etc, plumbing, electrical (of course), and some HVAC as well.

I need some help building a small house 24x24 (but might expand one dimension 16"-32"). It is a very simple design. Block basement 2 stories above. I am using floor trusses to make clear spanning easy and attic trusses. I have been doing the design myself and 3d modeling it in sketchup. Right now I have a house site, an installed and approved septic, and electric run there with a transformer sitting just waiting to be energized.

Here is the trouble. On some of the nit-picky details I was getting help from a family member (an architect) who unfortunately died a few weeks ago in a tragic accident. I have reached out to some others, engineers and architects. Everyone who knows anything I have reached out to is too busy to help a self-build person finalize the stuff I need help with. I am hoping to either get some help here or if you happen to be a qualified person who can help, I don't even mind to pay for some assistance. I am under the gun a little bit to get things going as I am soon to homeless (again thanks to local housing market craziness) and I am insanely busy with my regular job. I am not sure asking the forum and bogging people down with amateur questions is a great approach. What does anyone think?

I need some assistance with footer sizing, wall details like is putting the door and windows here okay, header sizes, and one biggie is the porch coming off the second story bedroom I know it is possible with ledgers and such but how to practically do it is another issue and I do not trust the local framing crews to just "figure it out" (in fact I might be doing most of the framing so I don't have to worry about the labor situation around here).

I should mention that there are no building codes where I am building (it is in TN) so no permit requirements or red tape (except septic which is done and electric). Of course I wish to build better than the code minimum as I am trying to get a mostly maintenance free house that stands the test of time.

Thanks in advance for any helpful ideas and feel free to PM me (if that is possible on this forum, I am a long time lurker here on the forum, sorry) if you have an interest in proposing something to me.

Regards,

 

[DoubleStud]

Everything is on IRC and you just follow tables.

https://codes.iccsafe.org/content/IRC2018P7/chapter-4-foundations

 

[Eng16080]

Given your unique situation, your best bet might just be studying the IRC code, as mentioned above. The Wood Frame Construction Manual and other similar references should also be of value as well as general carpentry/construction resources.

I would try to get a local engineer on board if you can, but this type of project probably won't be appealing to most engineers.

 

[SWComposites]

and there have been some good framing articles in Fine Homebuilding over the years.

https://www.finehomebuilding.com/design

 

[met33]

I'm not a structural engineer, but I'm in the middle of a home build now. Although I have a builder and I hired an engineer for key structural aspects, I ended up doing a lot of the design work myself based on the IRC and other resources, so I have some opinions and experiences to share.

The IRC has most of what you'll need, but it takes a lot of study to be able to apply it correctly, even for simple structures. It took me way too long to figure out that the section on braced wall lines would tell me how many windows and doors I could put on each wall, how close to corners they can be, and so on. I could give many such examples... It just takes a while to find what you're looking for, and sometimes you'll miss things because you don't know what you don't know.

I also found the IRC lacking in some areas, especially footings and basement foundations. For example, the minimum anchor bolt spacing of 6' is too far apart IMHO if your basement walls are on the taller side, are backfilled most of the way, and/or if you have clay soil. I'd suggest looking at Minnesota's amendment to IRC section R404.1, which recommends shorter anchor bolt spacings: Link.

I also think the minimum footing thickness of 6" is on the thin side, and I question whether plain masonry basement walls should be built so tall... Many of the failed basement walls I've come across while researching my build were plain block walls.

Some other thoughts:

1. Getting a geotechnical engineer to evaluate your homesite might be worth the money, given that you're building a basement. Soil bearing capacity (for proper footing sizing), depth to bedrock, water table, etc., could affect your foundation plans.

2. Overbuild your foundation if you can afford it. It's one of the most expensive things to repair in the future if it proves to be inadequate. A few extra yards of concrete and some extra rebar will seem practically free compared to a repair.

3. When I was looking into floor trusses, my engineer advised me that bottom chord bearing floor trusses on basement walls might not be able to adequately transfer lateral soil pressure (from the basement walls) into the subfloor diaphragm. He recommended adding plywood gussets on the ends, and some Simpson hardware, but I ended up going a different direction with my floor system. I'm not saying he's right, and I'm not saying you need gussets on your floor trusses, but I was surprised by it so I figured I'd mention it. If your basement walls aren't tall, or if your backfill isn't too high, it might be of zero concern.

4. I've spent a lot of money on my basement and related items, in order to have a tall, dry, finished basement with open spans and minimal risk of future structural problems. In hindsight, I might have decided to put that money elsewhere if I'd known how much it would end up costing. A standard height basement for utilities and an unfinished shop and storage is another story, and would be much more economical.

5. The WFCM high wind construction guides have some nice foundation and framing details. Here is the 150 mph exposure C guide (there are others): Link

6. If I were building a deck, I would consider making it free standing to avoid potential water leaks and wood rot issues at ledger connections. For a deck on the second story, I would want an engineer to design it and its footings/foundation.

7. Just my personal opinion, but I really like the Simpson SDWC screws for creating a continuous load path from roof to foundation. They have some nice framing diagrams for making all the connections on the Simpson site. FastenMaster makes a similar "FrameFAST" screw that basically does all the same things.

8. I used the ForteWeb software for preliminary design of floor joists. It's free and there are YouTube videos showing how to use it. It can also be used for headers and other things, if you know (or can calculate) the loading on them.

9. You should check to see if you're in one of the higher IRC Seismic Design Categories. It will affect everything in your build, starting with the foundation. Here is a PDF with some maps: Link

10. The APA has several great YouTube videos on meeting prescriptive code for braced wall lines, building for wind resistance, seismic resistance, etc. Those sections of the IRC made a lot more sense to me after watching some of the APA webinars.

 

[JAE]

So you say you know this, but this site is not for people to get free engineering services. It’s intended to be a site where engineers get tips from other engineers in their field of practice.

 

[Beenjammin]

All,

Thank you for the replies. I have looked a lot at the IIRC tables and various fine homebuilding articles in the past and also I have a copy and have studied several sections of the referenced wood frame construction manual. All of those resources are very helpful. However, they do not address everything I have some concerns about.

@met33: thank you for sharing your research and experiences.

On the foundation, yes I agree about what you say. Soil bearing capacity is something I have studied. I also noticed the new IIRC code seems to have changed for basement CMU hollow vs partially or fully grouted. I referenced local code in the most populous county two counties over where I also self-build a basement shed with a 1st story office (which was given away with the home thanks to a divorce which is the reason why I am trying to get adequate housing at this time) at any rate I noticed the references have changed to different footer thicknesses in the new code version. My property is steep and originally I was going to but the house on a hillside but the soil is fatty clay and would have required tall basement walls and the septic was going to be an issue with pumping etc. So I moved to the top of one of the hills (which also has a beautiful view). Up there I have excavated out about 6 feet and it is very hard rocky gravel soil, a 20k LB excavator can barley dig it (in fact some clean up with a jackhammer in the interior where the slab will be is needed. So I think my soil bearing capacity is very high. Also the chances of a lot of lateral pressure from the soil is unlikely based on my understanding plus I intended to fund the local rock yard (more than I already have with my 2000' driveway) to backfill to grade with gravel and then cover it with decorative stone. Furthermore, the basement will be walk-out so only one side will be under earth (the sides slope down relatively steeply) and I expect the basement walls to be 8' finished inside space with at least two CMU block above grade after it is all said and done. The first floor trusses would run perpendicular to the tallest backfilled wall however there is a staircase parallel to this wall so no all of the trusses run the full length for lateral support. As a example, this is one of the questions I have is about this. I don't care to reinforce the wall more or have some external buttresses or whatever. I just need some basic guidance. And how much I fill the blocks affects the foundation. I know it is not terribly difficult to solve these questions but I don't trust good-ol-boy advice if that makes sense and apparently I don't trust myself because I want some reassurance.

On the floor trusses, I need the open space so clear spanning is a big advantage for me. One of the questions that I have is supporting the two floors above because there is no double top plate on a floor truss supporting the floor above. I know from some research and having seen other builds there is a 2x rim band that can serve the same purpose but I am not sure how to size it. That is not something I saw in the IIRC.

On the ledgers, yes I was also trying to avoid the ledgers as well. That said the porch will be not very big and will be covered. The top level is a bedroom/basement and I want a view of the mountains from an upper porch. Think something like, 6' x 12'/15'. And so I am simply trying to figure out the best way to bring the roof out over it or if it needs to be the full length to make the roof work. Again, it isn't complicated, people do this everyday, I just want to do it the right way.

So it is questions like this that I am trying to solve properly.

@JAE I didn't ask for free engineering services. In-fact, I even stated I am willing to pay for some guidance since my architect died. I was kind of hoping someone might read this and say, oh I licensed in TN, I can help you out and here is what it might cost, let's talk or perhaps they know someone who could and would be willing to help just they this forum helps people. And of course I appreciate the resource sharing others provided. It is also why I put it in the general section because people ask a lot of different questions some as trivial as mine not related to building a skyscraper so I thought it was okay.

 

[Eng16080]

met33, you have a lot of good knowledge for not being a structural engineer. I agree with most of your points. In particular:

Overbuilding the foundation is something I often do, at least with the footings, especially if there's any concern with soil conditions. The cost of a 30" wide versus 24" footing is rather insignificant in terms of the overall structure cost, and as you say, foundation problems are not easy to fix after the fact.

The 6 ft anchor bolt spacing issue has been discussed excessively here. The bottom line is it doesn't really work by the numbers but seems to be one of those things that the code writers (and their lobbyists) aren't willing to change. It's a combination of the "it's been done this way for ever" argument and resistance by home builder associations. At least that's my take. In general, the top of foundation wall into floor diaphragm load path is something that is often not properly accounted for (by most engineers), yet it's generally rare to see a problem (in my experience).

I agree that a 6" footing seems too little. I would never go that shallow. Usually 8" or 10" for residential.

For decks, my preference as both a homeowner and engineer is to make them freestanding. The connection to the house is difficult to waterproof correctly and is the source of most deck failures, which usually occur 20 or 30 years after being constructed.

I'm wondering what your engineer actually did on the project. It sounds like you did everything that I would normally do if somebody hired me!

 

[Eng16080]

On the floor trusses, I need the open space so clear spanning is a big advantage for me. One of the questions that I have is supporting the two floors above because there is no double top plate on a floor truss supporting the floor above. I know from some research and having seen other builds there is a 2x rim band that can serve the same purpose but I am not sure how to size it. That is not something I saw in the IIRC.

Do you have a sketch of this? Are you saying the trusses are bottom chord bearing and you're not sure how the load transfers from the wall above into the wall below?

 

[bookowski]

Here's my $0.02 given your description.

You've got a square box with clear spans, I'm assuming a simple gable roof even though you didn't state that. If that's the case then there isn't that much engineering that I'd worry about in terms of sizing members (trusses will be sorted out for you by the truss guys). In terms of structure what you're going to struggle with the most is the detailing. You're unlikely to undersize anything so much that you have a major problem, but poor detailing could be an issue. I don't think it's worth you trying to solve the detailing yourself. I would recommend that you draw an overall section through the house, each way, at each unique condition, some simple elevations, and do some brief research on how you think that things may be detailed - that would be every connection/load transfer point (thinking about all relevant directions up/down/lateral). Circle each of these connection/detail areas. Then do your best to convince a local engineer to sell you a half a day or a day to meet you on the site, mark up your sections/details, give you notes, make sure that there's nothing obviously funky on site. Maybe record what he says, you can get a lot more info fast by talking than drawing. You want to make it as easy and clear as possible for whoever you find to help. Spoon feed it and you'll get a lot more out of it. If you just have a list of random questions you're going to get a lot of random answers.

I'd suggest the same for architecture. Even if you don't care about aesthetics it's worth it for the functional aspects and even money saving tips. This sounds like you're on a tight budget. An architect should be able to help you lay things out to simplify your plumbing, electric, hvac, etc. and save you more than he cost you. You should also get their input on envelope details. Improper flashing of a window etc. will cost you 10x more than the architect, never mind the headaches. Water and air leaks are probably the source of 90% of problems, spend your time on those details and also reviewing them and enforcing them in the field.

I'd also say that with a small house getting a good layout is more important than a larger house, less room for error or future reshuffling. A small house can be great if done well. Another reason to at least get a day from an architect. Again, if you're on a budget try to create a shell of the documents that is extremely clear and lets someone focus on helping you efficiently. You'll probably have trouble finding someone interested in a days work so make it as easy as possible for them (and promise that once the day is over you're not coming back next week with half a dozen follow up questions).

Good luck.

 

[met33]

Eng16080, thank you. I live in a rural area with minimal permit requirements and no residential engineering requirements. This makes it difficult to find structural engineers who are well versed in residential work, since there's not much of a market for it. The net result is that I learned a lot out of necessity.

Beenjammin, it sounds like you have a great homesite. With the foundation and framing you're describing, I would want an engineer to at least do a basic plan review and identify any areas that need to be engineered. This is easier said than done in areas that don't require residential engineering.

Regarding floor trusses, my experience was that very few engineers I spoke with have experience with them, and you can't count on the truss company to help you with the load path. They'll typically add a 2x4 top ribbon and let you figure out the rest. The 2018 WFCM has a detail showing a 2x4 top ribbon that is supplemented by blocking to transfer loads from above to below (Figure 2.12a). This article from Structure also gives some guidance: Link

 

[lexpatrie]

Well, I appreciate the post title......

I would contact the local structural engineer's association, there are "small guys" (like me) who do this kind of work, though as you already know, speed isn't something to expect, really. A lot of the "small guys" are actually one guy, and skill and qualifications (for the layperson) are tough to judge, but there's always the "he sounded nice and actually called back" criteria. If somebody rubs you the wrong way it's probably better to move on.

Another route might be the local "home design" services (usually drafting technicians, they've got a potential in road with an engineer they know, if you ask.)

On the wall pressure, I'd rather have the trusses on top of the CMU wall than stuck inside the walls.

Given the footprint I'd not absolutely be looking for geotechnical, unless there's that "hole to the earth's crust" that runs across your site like the one I got to handle in Hendersonville. ( At least I think it was Hendersonville), I'm not currently licensed in Tennessee, although they have decided I am not dead anymore.

The only way you can PM people off this site is some profiles have little riddles with their email addresses, or the feedback on the FAQ section will send an email to the creator. It's not set up for that.

 

[Beenjammin]

Thanks to everyone for the responses.

@ENG106080 thanks for you comments. Re: "Do you have a sketch of this? Are you saying the trusses are bottom chord bearing and you're not sure how the load transfers from the wall above into the wall below?". Yes it is related to load transferring through 2 levels of floor trusses. I do have a 3d model I made in SketchUp maybe later I can share if it makes sense to.

@Bookowski yes it is a trussed simple gable roof so all loads bear on the exterior walls and all trusses run the same direction top to bottom how I have it drawn out. Thank you for the excellent points on meeting with someone, duly noted.

@MET33 Thank you, I have a great spot, it is making lemonade from life lemons in this case and I got really lucky too. On the truss alignment with walls topic vs not, I have researched this also and wanted the expert opinion as well.

@lexpatrie Thank you for the suggestion, I had not thought about a local chapter. Based on your suggestion, I found this:

https://tn-sea.com/index.php.

It turns out that the president of the local chapter for my area works for a firm that I used to call on the EEs back a couple jobs ago. I will contact him and see if he has some advice for me of people that might be willing to assist.

Thanks again everyone, really appreciate it.

 

[Eng16080]

Re: "Do you have a sketch of this? Are you saying the trusses are bottom chord bearing and you're not sure how the load transfers from the wall above into the wall below?". Yes it is related to load transferring through 2 levels of floor trusses. I do have a 3d model I made in SketchUp maybe later I can share if it makes sense to.

It would probably be best to send a rendering (view) of the area and not the entire sketchup file. (Most people probably don't have sketchup and won't necessarily want to put that much effort into figuring out what the issue is even if they do.) In any case, I think I understand what your concern is. As I think has been already mentioned above, you want what's referred to as a ribbon board. Basically the end of the trusses will have a "cutout" where a piece of continuous framing (the ribbon board) is attached. Alternatively, you could use a full depth "rim board" (same depth as the truss), perhaps of LVL material (to minimize shrinkage) which would be attached to the end of each truss.