Slab or Crawl

The are many differences between a slab on grade / concrete floor and a wood floor system.  The main topics surrounding both systems are heat differences, durability, and future repairs.  Let me start out by defining each in as few terms as possible.

The slab floor is usually 4 inches of poured concrete on top of compacted soil and when finished is even with the top of the foundation wall.  The wood floor is typically built on top of the foundation wall with joists spanning from end to end where possible.  There are other applications of course, but I’m concentrating on the wood floor system that rests on top of the foundation wall.  Let’s move to the pros and cons of each.

Slab: 

• no steps
• no squeaks
• impervious to minor flooding
• permanent
• repairs to plumbing very difficult and costly
• less expensive to install tile
• stays cold, in floor heating very expensive

Wood: 

• steps likely
• squeaks possible
• may need replaced due to minor flooding 
• semi-permanent
• repairs to systems not difficult in crawl space
• less expensive to install hard woods
• stays warmer because it’s wood and insulated

That’s the short of it, here’s the why:

The concrete slab makes it possible to eliminate steps depending on the grade around the home.  With a crawl space you typically have steps although there are ways to eliminate those.  With a concrete slab floor you don’t have a crawl space to enter for maintenance, or a place for bugs and possibly animals to hide.  The main issue with not being able to access underneath the floor is that your plumbing is still located underground.  If the plumbing underneath a slab floor were to fail then you have a fairly large job of removing concrete to get to it.  That being said, the instances of that happening are relatively low.  The overall life of the systems below the slab is certainly debatable, but that’s another post altogether.

Concrete is a fairly permanent application with little movement in it.  Like all materials it contracts and expands with the changing temperatures, but it is not generally noticed by homeowners.  The wood floor system is made up of a bunch of smaller parts.  Everyone is probably aware of the squeaks and other noises associated with wood floor systems.  This can be taken care of by proper installation involving adhesive and even screwing down the sub floor, but nothing says squeak-free like concrete.

Heat loss or gain is another area to consider.  The concrete slab lays on a bed of crushed rock and fill dirt.  The only way to maintain heat in the slab is by laying a heating system inside the concrete.  This is fairly expensive in our area since our winters are fairly mild, and it is a practice not used by many.  The colder floors are normally noticed when tile is laid directly on the concrete which transfers the cold to the surface.  There’s no way around it, it stays cooler than ambient temperature.  The crawl space and wood floor system will keep the tile noticeably warmer, although there is a greater expense on the installation of tile on a wood sub floor than on concrete.  Likewise, if you are leaning towards hardwood flooring, installation on wood is much easier than on concrete.  You can nail directly to the wood depending on your product choice, but with a slab, some manufacturers require glueing the hardwood to the concrete which adds quite a bit of labor. 

I have lived on both floor systems with the last 15 years of my life spent on slab floors in three different homes.  For a number of different reasons slab is still my first choice for a one level home.

This article is based on my experience as well as information gained from knowledgeable people in the industry.  The above is the opinion of the author.  I would love to hear your opinions on this topic.