Basement Concrete Slab Expansion Joints

I have a 32 year old home with a full basement. The floor was poured with the black fiberboard around the perimeter of the basement but has completely rotted away in places.

During the May 2010 floods here in TN the pressure of ground water caused water to shoot through these gaps and flood the basement.

I need to dig out this old material and reseal all the way around.

Do I even need expansion in a buried basement? Isn't temperature basically constant?

A Tennessean

Hi Tennessean,

The water shot up during the flood due to intense ground water pressure (hydrostatic) under the house (due to the flood) and if it hadn't come up through the expansion joint it would probably have caused the slab to float and/or severely break apart.

At any rate, a slab does shrink or expand from drying or temperature changes or as the sub grade compresses a little.

Basements are not usually subject to extreme temperature changes, but even in TN the slab temperature can vary considerably if the basement is not heated in winter. I lived next door to TN in NC for 27 years and I know what your weather is like.

At any rate, expansion joints are required by most building codes partially because no one knows how long the basement (foundation) will be uncovered or unprotected. I have seen basement slabs poured and left for weeks before construction of the house commences.

So, if the expansion strip has disintegrated or rotted away, dig, chip or chisel out what’s left of it and remove all the loose pieces with a vacuum cleaner.
Buy a new expansion strip and cut it to size. Slide the new strip into the joint and tap it with a piece of wood scrap until the top is 1/2 inch below the concrete surface. Caulk the joint with an elastomeric sealant.

Or, the top part of the bad expansion joint can be cut off and the space filled (Caulked) with an elastomeric sealant.

Sump Pump

You may want to think about putting in a sump pump (see above photo) with a battery back-up to protect your basement from future catastrophic occurrences or if groundwater is a continuing issue.

Good luck,
Carl

Walkout Basement Walls

What is your opinion about building a walkout basement with concrete on all sides except for the wall where the walkout door would be? Is it structurally as safe as a complete concrete structure or are there any issues to worry about, especially in case of flooding?

Sonia

Hi Sonia,
A walkout basement needs to have concrete walls for structural strength when the walls are less than 18” above finished grade (dirt), then conventional wood framing can take over.

Concrete walls, no matter what anyone else tells you, are always damp and cold...always…in any climate and in any season. So, it makes sense (and cents) to switch to wood as soon as the finished grade allows.

As for the wood framed walls strength, there is no dirt pushing on the wood framed walls, no hydrostatic pressure either as the wood framing is above grade, so the wood framing is fine.

As for the flooding part of your question, I hope you mean minor flooding such as flooding caused by a leaky basement.

One of the main advantages of a walkout basement is the fact that with proper waterproofing and drainage, the chance of a flooded basement is greatly reduced.

The chance of flooding is reduced because rain and runoff water have gravity helping them go around the structure and drain away from the house on the side where the wood walls are “at grade”.

A sump pump is still required with a walkout basement by most building codes, so that tells you that a walkout basement is not immune to flooding.

But flooding is irrelevant as to whether the walls are concrete or wood.

Carl

A House Is Only As Good As Its Foundation

I seriously want to buy a 1935 pier and beam bungalow.

It has had a lot of work, work that was done right according to my inspector.

But there are some things that still need to be done.

I just am not sure in what order to do them.

The big things are leveling, roof, replace a tub with a shower stall and refinish the hardwood floors.

Electrical and plumbing are very good and updated, as is the kitchen.

Can you help me figure out an order of priority?

Janet


Hi Janet

I would start with the most important item 1st, leveling the house.

A house is only as good as its foundation.

Courtesy: Foundation Repair Network

You want to take care of this first as the settling can and will continue and other major problems could arise, such as plumbing leaks, uneven floors, doors that won’t close (or open), etc.

As houses settle, they do so slowly (usually over many years) but they (the walls and floor joists) take the plumbing pipes with them. This slow settling process usually does no harm to the plumbing as the pipes are bent (or twisted) very slowly over time.

Leveling needs to be done as slowly as possible (months) so as not to stress the plumbing pipes but rather, slowly move them back to their original positions. Unfortunately, some pipes or seals may break during the leveling process.

Leveling needs to be done by a professional. It is not a DIY project.

It’s not real expensive; it’s just an agonizingly slow process.

Also, have the cause of the settling investigated and repaired if necessary. (Read “Foundation Sinking Repair”)


Depending on the severity of the settling, you can move up to the top of the house and re-roof while the house is being leveled.

I would not touch any plumbing jobs or refinish the floors until the house is level.

Hold off on the plumbing as the pipes in the walls and floor joists should not be tampered with until they are stable.

Hold off on the floors because as the house is brought to a level position you will see unevenness in the wood floors appear (if they aren’t uneven already). Refinishing will (should) fix these uneven spots, so wait till they stop being created.

When the house is level and stable, then do the bath and then do the floors.

You can find pros and cons to do the floors first, but I have always made floor finishing the last thing…after everybody’s out of the house for good.

I’d rather have the dust from refinishing to clean up (it can be controlled somewhat) than have to refinish the floors again because of scratches from tradesmen.

Then, clean up the dust and enjoy your “gem”.

Good luck,
Carl