Is it OK to change label alignment inside a form if labels vary greatly?

Question

I am designing a form that asks for a lot of data in the form of

Short Label [text input]

However, in between all those short labels there's suddenly longer questions such as:

Are there other buildings on or near your current building site?
( ) no
(o) yes,
    registered as: [number]

and finally, classical opt in/opt out checkboxes like

[x] I already have the required documents for this builduing site.

Without giving it much thought I used left-aligned labels for the short input prompts, but top-aligned ones for the longer questions. Then I read more about the whole alignment issue in Luke Wroblewski's book "Filling in the blanks" and he strongly advises against any change in label alignment inside a single form.

No I am left with the following bits of information from the book:

Top aligned is suitable if the form should be completed quickly and information is well known.

We have several prompts for post addresses, which would fit the description, plus: top-aligned would allow me to arrange fields in the well-known layout (street/nr in one row, etc.) and still have separate labels for them. Also, this would not result in a change of alignment for the long text questions.

Left aligned slows the input process, but can be advisable if users need to consider what they enter and makes it easier to scan the labels

After the addresses there's technical data to enter, which is not well known and which users will possibly want to scan to better understand the context. Plus, top-aligned simply looks... dragged out or unnecessary lengthy for this multitude of really short prompts. (Coordinates, power usage, some this/that/other radios)

So, firstly: When deciding for a unified alignment for the short ones, both options seem equally reasonable to me. Is there any other effect of the alignment that might tip the scales one way or another? For example, I assume that separate top-aligned labels for street/nr/zip code, etc. make the form more accessible for screen readers (as opposed to one compound label for each row to the left) - but I haven't looked into this yet.

And secondly: If those short ones were set to be left-aligned, this would result in multiple-line labels for the textual questions, which I think breaks the reading flow from question to answer. Would this be enough to warrant a change of label alignment between the short prompts and the textual questions?

In any case, are opt in/out checkboxes a special case, which can be positioned at the start of a line, or should they also align with other input fields? (I have seen both on the web)

Answer 1

I think the answer here is to understand the rules, and throw them out if they don't work for you in this case. But take a look at the whole form before making decisions - does it look consistent? Does it flow smoothly? Have you asked other people with less invested in it what they think?

As long as a particular type of input is consistent, and the flow through the form feels smooth, then it should be OK to play about with alignments. But make sure that you are doing this for good reason (as it looks like you are), not just for convenience.

The only one I would have questions about is the check boxes, which may be better aligned to the right of the questions. These require going back to the left after reading across to the right. All of the others maintain the top left to bottom right flow, well enough.

In my opinion, of course, and based on what you have said. But keep the main flow in the right direction and you should be able to play with the details a little.