Calling All Plumbers and DIY – Tips on Remodeling a Bathroom

Remodeling a bathroom

Hello all, so we were thinking back on the many crazy situations we as plumbers run into on a day to day basis. The one thing that kept creeping back up into my head that may sound simple but continually poses problems to both the professional plumber and do-it-yourself homeowner is the rough-in and trimming of a bathroom. We know, we do this everyday it shouldn’t be difficult right? In the following article we’re going to give you the difficulties that can and will pop up from time to time on both the professional level and in the home.

O.K. so you’ve been asked to put a bid on some bathroom remodeling for a school in your area. Most times in this situation you’d receive a set of bid documents in order for you or your company can put together pricing for the job. For this article we are going to focus on the fixtures and trim and we will start with the lavatories because quite honestly its the part of the job with the most inconsistencies.

Remodeling a bathroomLavatories – So the plans are asking you to provide new lavatories for the project, here are the questions you have to ask yourself before providing a bid and or doing the work.

**As a side note the things mentioned below happen quite often. They are not uncommon in fact we see these issues on a weekly basis so it is a good practice to have these questions in an accessible part of the brain.

  • What type of lavatories are in the existing space? Are they wall hung? Are they drop-in? Are the existing bowls integral to the counter top (are the lavatories molded into the counter i.e.Corian or terrazzo?)? Why is this an issue? Because many times a set of drawings will have inconsistencies with what is to be installed and what is existing, for instance the drawings call for all new drop-in lavs but the counter top is to remain. However when you look at the job you find that the lavs are integral to the counter. This means the entire counter needs to be removed.
  • Another huge issue is lavatory size. You may see a specification call for wall-hung ADA lavatories which can be quite large, if the proposed bathroom is fairly old the existing lavs maybe small. Check the dimensions of the bathroom to see if you have enough space in the room  to accommodate the new lavs.
  • If the existing counter top is to remain and you’re just removing the existing lavatories and replacing with new, make sure the new lavatories fit in the existing opening. This applies to both undercounter mount lavs and drop-in lavs. Check the specifications.
  • Take extra precaution when dealing with lavatory faucets. Make sure the spread of the faucet matches the spread on the lavatory i.e. having an 8” center widespread faucet specified for a 4” center lavatory bowl or having a 4” center faucet specified for counter top that has existing 8” center holes drilled.
  • Depending on where the new lavatories are being installed, are there thermostatic mixing valves specified? They are code almost everywhere but are missed quite often on specs. Ask the question from the architect or engineer. Just let everyone know you’ve got it covered or that it isn’t specified so you’ve excluded it from your proposal. Either way you’re covered.
  • Is p-trap, stop and supply insulation kit specified? If the lavatories are ADA compliant insulation kits will be required. Make sure you have it covered or that it isn’t specified so you’ve excluded it from your proposal.

Water Closets/Toilets – There aren’t quite as many issues with water closets but there are some and here are the ones that will make your life miserable on occasion.

  • Make sure you know the rough on the existing toilets. Are they 10”, 12” or 14”. The waste rough in dimension on a toilet is the measurement from the center of the waste opening to the finished wall. Putting a 10” rough toilet on a 12” or 14” rough opening isn’t pretty and most times if the opposite happens the toilet won’t fit.
  • Many times when remodeling a commercial or institutional bathroom the owner will want to change out tank type toilets and install water closets with flush valves. As plumbers we love the thought but most buildings will need to have the branch piping upsized to accommodate the increased need for water.

Thanks for reading and we hope this helps when looking at a bathroom remodeling project.



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  1. When you say, in the last paragraph, “remodeling a commercial or institutional bathroom the owner will want to change out tank type toilets and install water closets with flush valves”, does this mean adding the inside wall mount steel frame and tank system, like geberit? Or did you mean something different. I have been planning some residential retrofits in my home with the wall mount system to make cleaning WAY easier, and I’m concerned I had not considered additional plumbing requirements for needed water — or did I just interpret your comment incorrectly? Which could be TOTALLY possible!

    1. Yes, I meant wall or floor mounted commercial toilets with separate flush valves either external or behind the wall. You should not need to upsize your water piping for the in-wall Geberit flush fixtures. Thanks for the comment, I’ll be honest I didn’t even consider the Geberit flush system when writing this article so I appreciate you asking the question. We’ve installed quite a few of those toilets and they work pretty well. Please be sure to find a plumber that is familiar with this type of flushing mechanism. You don’t want yours to be their first. We installed these in a controlled environment so we would get the hang of them before installing for real. If you need any help choosing a contractor in your area let me know where you live and I’ll gladly help. You can email me that information.


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