(Structural) engineer or architect?

Someone I know has a basement which only extends to about 3/4 the width of her house; the rest is a crawl space. The part with the crawl space also has only one floor above it, while the part with the basement has two floors above it.

She is thinking at this time of having the crawl space part dug out and the basement extended under the entire structure. But she’s also thinking of at some point down the road of adding a second floor to the part of the house above what is now the crawl space. So she’s concerned that whoever redoes the foundation now should make it strong enough not just to support the one floor which is currently above it, but also to support the second floor that she might one day add. Question is what type of expert she needs to make sure this is done correctly.

Personally I think of an architect as someone who can draw up plans for what needs to be done and an engineer as someone who assesses what’s already in place. Since much of what’s being contemplated here is already in place (i.e. the first floor plus the crawl space foundation) I’m thinking engineer. But perhaps it’s really supposed to be an architect.

You need an engineer to confirm the plans are safe. A reputable architect would arrange everything.

An engineer would be able to design a safe foundation as well as verify someone else’s design. An engineer might not come up with as interesting a design as an architect, but it would be safe, assuming he/she knows in advance that it would eventually hold 2 stories.

I would think the architect is who you go to, and they will have their work checked by an engineer. The architect should be reasonably competent at the engineering stuff, otherwise they would have to keep revising their designs.

Although architects have a familiarity with building codes, they are generally not trained in performing detail structural analysis and selecting structural materials and components to meet building code structural requirements. On new building construction, the architect often works hand in hand with the general contractor to execute the architectural design, and the structural engineer will work with both (probably retained by the architect but can be hired separately by the general contractor; it just depends on the arrangement) to ensure that the design meets structural requirements (including, depending on location, seismic, wind, drainage, and other requirements) and that the requirements are correctly executed in construction (e.g. the correct width and spacing of studs in load-bearing walls, bracing, et cetera). The structural engineer is ultimately legally responsible for the integrity of the structure and if building within a municipality will have to sign off on final as-built plans with their Professional Engineer stamp.

In the case of add-on foundation work as described by the o.p., it is probably unnecessary to obtain the services of an architect. The plans (foundation drawing and specifications) can be prepared by the structural engineer as part of their work. If you are hiring a general contractor to oversee the work (recommended) they will hire the structural engineer and deal with the permitting and inspection, and while they are at it can evaluate whether the existing basement foundation is adequate to support a second story. (Almost all residential basements are capable of supporting two and even three stories by default, but if this is an older house or one that has been built piecemeal it is good to check this out before starting the whole process.) The general contractor will hire the excavator and oversee the reinforcement to support as well as the contractors that pour the new basement and do any finishing work. Building a new foundation under existing structure is fairly specialized work so you want to find a general contractor who has experience with this and has contractors who know what they are doing and are fully bonded.

For adding a partial second story, you’ll almost certainly want to consult an architect, but if it is just a basic frame out (e.g. just adding a room connecting to the existing structure) they aren’t really going to be doing much more than drawing a construction plan. Depending on what that structure is and the applicable building codes you may or may not need a structural engineer to do anything more than a consult to verify that the plan meets codes and there aren’t any gross errors such as excessive spans and unsupported load bearing walls. You’ll mostly be relying on the general contractor and his framer to construct and do any modifications to the existing structure to secure the new framing to the first story, hence the need for a good general contractor.


I don’t think any of this is correct.

I once had a house built, and though we had a general contractor, he was a very hands off guy and I dealt extensively with all the subcontractors directly. There was no structural engineer involved. The architects plans contained all the details about which material (type, size etc.) was used for which part of the structure, including all details such as width and spacing of studs etc. etc. Plans filed with the township were signed/stamped by the architect only. (The contract with the architect called for him to make inspections at various points along the way, but the real inspections that mattered were done by the local building department.)

Perhaps it’s different where you live. (This is in NJ.)

It varies from jurisdiction to jurisdiction. In NJ, at least according to state law, an architect can taake responsibility for most such projects, though the municipality can insist on more.

Reputable architects or GCs will be familiar with local and state/provincial/territorial law. It would be very unwise to take especially specific advice from anyone else, not only for obvious safety reasons, but just because of the fact that every place will be different in terms of what the law says and how to best interact with relevant authorities.

I believe that in PA, at least, licensed architects are required to have engineering training. I had an uncle who was an architect who told me that Louis Kahn (whom he knew well) was the last architect in the state without it and he had to have an engineer approve all his plans.

If your general contractor was “a very hands off guy” and you had to manage the subcontractors directly, what was the general contractor even doing to justify his fee beyond pulling permits? Coordinating subcontractors is (or at least should be) the job of the general contractor and is why they get paid a significant percentage of the construction cost.

I’m not familiar with building codes and requirements in New Jersey, and it may be for residential construction that approval by a “licensed professional” is not required (especially if it is not in a large municipality) but in seismically active areas some type of structural assessment is generally required in large municipalities even when it is just a modification to an existing structure, which is a real pain in the ass when you are just extending a room or putting on a sun porch. Whether that can be done by a licensed architect or requires a structural engineer depends on municipal codes and the type/use of structure, but I would assume anything that modifies the foundation will at least require an evaluation of soil compaction and drainage. Then again, I’ve never worked on individual standalone residential construction and it may be fore structures under a certain square footage and height that structural evaluation is not required as long as it falls within some pre-specified conditions.


That’s really it- the architect will draw up the plans for the additional space, but the engineer will verify those and more than likely draw up an engineering drawing showing the details of how it needs to be made.

So you’ll have a architectural drawing showing how the space should look- dimensions, where, how, etc… and then an engineering drawing showing the nitty-gritty of how it should be built- what sort of wood, what sort of foundation, fasteners, etc…

The kind I’m most familiar with is municipal design type stuff- I used to work for a civil engineering firm in college. We’d get the “land plans” from the architects- they’d show how the streets were to be laid out, what sizes and arrangements the lots would be, and all that sort of thing. The engineers would take that and translate that into a series of drawings that would show what sort of concrete the streets would be made of, and how thick it needed to be. It would also show where the water, sewer and drainage pipes would be, how big they’d be, what they’d be made of, how deep they’d be, and so on. The construction companies used OUR plans to build the subdivisions, not the architects.

I agree that the general contractor would be the one who would determine if an engineer is needed, and engage them. When we had our closet/bathroom redone, we had an architect (a buddy of mine) draw up how we wanted it to look, and the GC just built it off that- no engineer needed. But it wasn’t structural work, just framing and drywall for the most part, with some plumbing rearrangement.

As someone who worked with both disciplines, most design firms have both architects and engineers on staff, or have contracts with same. As mentioned, the architects do the design and the engineers tell them whether or not it can be built as designed, structurally, mechanically and electrically.

He hired, and (for the most part) paid the subcontractors, ordered the material and the like. However, once the subcontractors were hired or showed up, I had kind of a free hand to deal with them directly in terms of exactly what I wanted done, who was doing what, when they were scheduled to show up, and the like, without having to go through the GC.

It was really an ideal situation for me, actually. (It also helped that the GC was a great guy, personally, and in addition to being hands off, he was also pretty flexible about all sorts of things.)

The International Building Code assigns the same foundation requirements to residential buildings that are “two stories or less”. Adding a second story is not a higher class of foundation. When I added a second story to part of my house in 2005 I specifically asked the chief building inspector if I needed to dig up part of the foundation to inspect the width. He said “No”.

I did consult a Professional Engineer I knew concerning some non-standard construction for the new roof structure I designed to cover the entire existing portion of the house. Previously the house had a main section with a hip roof and a wide enclosed porch with a shed roof. They were self supporting. I wanted to rip all that off and build a 30’ wide, high-pitched gable roof. This required tie beams to span the entire 30 feet to triangulate the roof. He approved my design but said I would only need to hire him to sign it if the city requested it. They did not.

Depending on the age of the building, what @mixdenny said is likely true. The more important problem I see here is trying to dig out a crawl space to turn it into a full basement. Logistically that’s very difficult and going to be quite expensive. The only access to the crawl space is likely from the basement, not from the outside, so it would need to be hand-dug and taken out in 5-gallon buckets. Slow and very labor intensive. Also, to avoid disturbing the existing crawl space foundations and footings, it could only be dug out to within a few feet of those, depending on the type of soil. So if the space isn’t very wide to begin with then there’s going to be even less usable space left. If the desire is to use the full width, then the existing foundations and footings may need to be demolished and replaced while also temporarily holding up the room above, somehow.

The other question then is how sound that room above is to begin with. While the foundation and walls are likely fine to build on top of (again, considering the age of the house, if this is some 1870s farmhouse that’s a much different story), the ceiling joists may not be adequate, nor the window and door headers, so you could be ripping off the ceiling and the walls above all the windows and doors. A job like this is very complicated and likely not worth the cost just to add some unfinished basement space and prep for a 2nd floor addition that may never happen.

I did design a 25’x25’ master suite addition for a client a few years ago who wanted the option to build a room above it later. That required making a wall down the middle a bearing wall, which it wouldn’t have been otherwise, and putting full size ceiling joists at 16" on center over it, and then roof trusses on top of that. The space where the stairs would go also had the joists headered off and then filled in. That way, if they do decide to add that room above, they just pull off the trusses and the infilled framing around the stair opening, with little to no damage to the ceilings below. Had we not planned for the future 2nd floor, then the roof trusses would’ve just clear spanned the entire addition with no bearing wall in the middle. The way we did it added a marginal amount of cost to the new construction, but doing it afterwards would be much harder and more expensive.

Sometimes tearing things down and building anew is cheaper than multiple changes. So she should look into the costs of removing the one story addition and crawlspace and building the new basement extension and two story addition all in one go.

You do not need an architect, but you will probably need a architectural draftsperson to draw up the plans. You certainly need an engineer, and you need a skilled contractor that knows what he is doing and how.

I am the latter, and I work with engineers often and we usually consult back and forth because they know what the end result needs to be but I know what the practical options are to get there.

A project like this can be expensive for what you ultimately achieve in the end. It may be worth it. There will be some foundation specialists in the area. I would talk to them first to get an idea what they will charge. Prepare to be shocked.

[emphasis added]

I didn’t want to be a wet blanket, but yes, digging out under existing structure and then figuring out how to pour a new foundation is going to be really expensive. It will almost certainly be a piecemeal pour for the floor alone, which means having a truck come out multiple times, as well as having to figure out how to support the existing structure and still have safe access underneath. If there is some particular reason for not just totally replacing the structure—especially since the homeowner in question is considering adding more structure atop it later, for which I assume it was not designed—then it might be worth trying to figure out how to temporarily separate and move that structure out of the way so a contractor can do a straightforward excavation using normal heavy equipment and a single pour. I’m sure that won’t be cheap, either, but at least you won’t have people excavating by hand in an overhead environment, and then figuring out how to get adequate access to even set up the forms and pour the foundation.

Either way, I have a hard time imagining that this scheme would cost less than new structure even with the current price hikes on materials. If the old structure is desirable because it is heritage construction or for aesthetic reasons, consider salvaging materials or reusing part of it as a façade rather than trying to build all around it. Having worked on rehabbing older buildings, I would say that a lot of older construction is really solid but was also never built in a way to accommodate additions or meet current codes, and can also come with some real surprises once you start getting into it.


The idea of tearing down an entire ~2,000 sqf house (plus 1 car garage) in good condition in order to add about 250-300 sqf to the basement is a complete non-starter.

It’s a ridicuous idea in any event, but it’s even moreso in this particular situation. The fact is that the impetus to expand the basement is not from the homeowners themselves, but the basement is primarily used these days as a meeting place for a social group/non-profit that they’re involved with, and that group needs more space and broached the idea of expanding the basement. The group is willing to pay some reasonable amount (if she commits to let them use the place for at least the next two years) but they’re not paying for rebuilding the entire structure and neither is she interested in moving out.

They were supposed to have a contractor come by last week to give an assessment (I had strongly advised her not to rely on this contractor’s assessment but to have a structural engineer/architect sign off, hence my question in the OP), but I haven’t heard anything from her since two weeks ago and don’t know how that went.

Possibly he said it’s not economically feasible, as people are suggesting. I actually saw a building in an area I frequent in which this was recently done (it was a house which was converted to an office building) and it didn’t seem like a huge deal from what I saw, but I could be wrong. Either this basement expansion will happen or it won’t, but one thing that will definitely not be happening is the entire house being torn down.

Nobody was suggesting tearing down the whole house, just the 1-story part with the crawl space and possible future 2nd-story addition. 250-300 sf is rather small and the overhead/cost per sf is going to be lousy, if it’s even feasible to do for such a small area. Without more information (age of the house, location, style, prevailing construction costs in the area, etc.) there’s not much more advice to be given here.

Which post recommended this?