slab vs post and pier

[Tink]

I have converted to "slab life" as I am getting bad knees and miss being high enough with post and pier to catch the trades, along with the storage/workspace below. But slabs tend to be a bit cheaper in the long run, as less wood framing is to be done, which creates a shorter build time. In my past "life" as a builder, Termites, and other critters are usually only found at piping penetrations, whereas a post and pier, termite infestation is every pier, and up the post, along with the pipes as well.
Inspection of a post and pier is easy, but a slab, most is hidden on the average slab home.
A way to solve this, is if you are building your own and choose a slab foundation is plan all your waste water along a single line main trunk pipe about 3 feet away from slab, then run your laterals (branches) over to the appropriate plumbing fixture. An example would be facing front of house, garage/lanai (laundry) next up would be kitchen sink, along entry way to bathroom lav(sink), toilet, tub. 90% of all your plumbing is now out from under your slab, so if replacement is necessary, no real disruption.
I have not had the chance to deal with the required Engineering for all house plans yet, but a slab is easier to pass as the seismic hardware is easier to place, for the positive earth transfer point is your slab. I believe post and pier with the new change would have to be a hybrid of a typical "T" footing where shear is needed with piers between.


Community begins with Aloha

[Carey]

SR: As far as most of the pros/vs minuses... the first consideration would be your lot....
A lot with a lot of thick vegetation cover around & high ground towards the edges would not get ground floor breezes in a house near the center of the lot, one that has less dense vegetation and a smooth mounding towards the center would

Shear wall foundations required now can take almost as much concrete as some slabs, depending on the lot, but if you want to build over an very uneven terrain, with minimal lot leveling, then P&P would be the way...
Some homes are also built with very uneven terrain below the house, so that there is a high build-up P&P on one side & another entry side is at or almost at ground level...

My advice would be first:
Totally explore the lot (this can take some doing with most undeveloped lots here)
Take inventory of the existing terrain, the plants & neighbors plants and terrain (and for that matter the neighboring lots in total...as many issues here are with how well neighboring lot "mesh" with the lot you would like to develop
Try to visit as many existing structures here (esp. in the area they are looking to build), to get to know how well different designs & building materials are for your in-laws
Meet with some of the builders (esp with the "kit home" building Dept. at the lumber yards) to figure out in-law likes/dislikes in current designs here (again, see if you can actually visit some of the homes they have nearby the lot)

This "ground work" will give you more appreciation for which design to choose, as the reality is that the lot may be more a determining factor that any of the pluses & minuses you have seen here

I am saying this as we had planned to build before buying our house (fell in love with the location...& this was the choice). We had been very apprehensive of a slab after reading many posts, but have never had the problems that many here had warned us of (less bugs than any of our P&P neighbors, great trade wind ventilation, no mold at all...) These are all a result of the lot lay & the building materials, not the slab... the slab has been a dry base... as any slab or floor base on P&P SHOULD be.... we have seen a lot a problems when slabs stay wet (water draining toward or under the slab, vegetation growing into walls on slabs -kinda a duh...but have seen it often enough here...things like that are more incorrect planning & maintenance)

ETA: regarding termites.... since there are both subterranean & drywood here, ALL wood is game, & there are also powder post beetles & carpenter bees, so ANY wood you use anywhere in your house will be under attack -some woods that are termite resistant like teak are desert items for powder post beetles & carpenter bees aren't eating the wood so will drill through treated wood if they get a bite hold, but prefer a nice old piece of wood, hopefully away from your house,
& EVERY building material has some agent here that will try to destroy it (all metal here oxidizes (even the titanium plates at Imiloa are showing some weathering) Concrete, brick, ram earth & other build up materials have earthquake issues, plastic can be UVed into submission, even glass gets etched here.... so have a great time planning!

[shockwave rider]

The in laws bought a lot in the Hawaiian beaches/shores set of subdivisions, I am not sure which one, but they don't have to do catchment in their neighborhood so no worries about collapsing water tanks.

The lot slopes gently up away from the street, it is on the Mauka side of the road. They want to build as far as possible to the back of the lot, which puts it on the high spot, and all the neighboring lots are either lawns with small shrubs and trees or small ohia and ferns. Some tall hala is the biggest thing on the lot at about 20 feet tall, there doesn't seem to be any amazing lava features to save, so they are thinking of just bulldozing the whole thing, the Ohia already are showing signs of ROD on this lot and all the neighboring ones, so going out of their way to save the few bigger Ohia probably isn't worth it.

[Hunt Stoddard]

They can try the hybrid approach, part slab, part P&P. As everyone has said, there are pluses and minuses to everything. The key to being satisfied with the outcome is planning and intelligence. Perhaps consult with a creative architect, though custom homes plans can be expensive. The flip side is a boring prefab or package home. As anyone can tell driving around, there are lots and lots of boring and ugly as hell houses here. Try to do something creative, other than bulldozing the whole lot and going with a package home. Of course, again, tradeoffs, "creative" usually means expensive. Houses on uneven terrain are harder to build and more expensive.

If you have an enclosed carport, you probably want it slab. Laundry room on slab is not bad either, and actually if you can put your bath(s) on slab too it's not a bad idea. Put drain/septic in the slab but everything else in the walls. Almost all baths here on wood subfloor have rot around the shower/tub.

One disadvantage to a slab house, particularly with hip roof is that if you want to make and addition later, you have to remodel the roof framing. There is no good way to extend the roof down further as you could with a P&P roof with higher eaves. A lot of times you see people with near horizontal addition roofs (which leak at the seam), or you need to resort to building a roof OVER the existing roof, which can be awkward.

If you go P&P consider making it high enough to actually make the space underneath usable. Four feet is not really "usable" unless you're a dog.