How to do incremental building of an addition
I would like to build an addition to my house and I would like to take an incremental approach.
Basically, I would like to have a contractor build the weather tight shell, the addition is two stories over a basement, and then I would like to finish the house in stages. For example, do the electrical wiring, then rough plumbing, then sheet rock, etc.
The reason for the above is that I do not want to borrow money to pay for the addition and I do have enough saved up to build the weather tight shell.
I did the same increment approach when we finished the basement of the house and it turned out to be a two year project because we have to redo the pluming and heating, pour a new slab, spray insulation, sheetrock the walls, etc. The local building department, Worcester MA, was good enough to keep the permit open for that period of time.
Given that this will be a one to two year project, I wanted to spray insulation immediately after the weather tight shell was up. The intent is to keep the interior of the addition warm enough during the winter so we could work in there.
So, I was wondering if I could spray foam on the exterior walls before putting in the wiring. I’m thinking of using open cell foam.
-David
Replies
Rough in the exterior wall wiring with some kind of raceway system EMT, PVC conduit or Smurf tube. Then you can run the wire later. Set boxes wherever you think you will want them (be generous) ands run the raceways to some accessible place.,
I did this with masonry walls in my addition and it worked out great. My origibal oplan changed but since I just had a raceway going to each box, they could be configured however I wanted. It may have added an extra hundred dollars or so to the materials cost but the flexibility made it worth it.
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I home run every box to a central J box so anything can connect to anything else but this is basically one room.
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David
Run the plumbing b/4 electric-wire moves around easier than hard pipe-same goes with heating.
Check with your building department again, make sure they will leave the permit open long enough, and make sure you know what must be inspected when.
You are making a lot of extra work by not getting the wiring in the walls. It's not difficult to cut channels in the foam and run the wires later, but it's so much easier I can't imagine putting off the electrical. Conduit will just add to the cost so I don't see the benefit.
You don't need to get everything in the wall, but I'd recommend getting your boxes and the wire roughed in.
Another option is to only have an inch or two of foam sprayed in now and top off the bay after your rough in inspections are passed and you're ready for sheetrock.
Personally I'd add 2" of rigid foam myself - at the stage you're at there isn't anything to get in the way and if you are careful about how you rip the foam it will fit snug but you won't have to force it. The last time I priced sprayed in foam I could install the pink closed cell for half the cost of the same thickness of open or closed cell - if you are doing the work it would be an even greater savings. Open cell foam is popular because of price and not performance regardless of what the guy selling foam has to say. If the cost of open and closed were reversed the debate over open vs closed would go away since closed is simply better.
Sounds like a great project :)
Quote:Conduit will just add
[quote]Conduit will just add to the cost so I don't see the benefit
I suppose that depends on if you are building a house to live in for a while or one you are selling.