I have a 1970 rental house that is prone to flooding the crawlspace approximately 1 week a year.

To clarify, the whole section of land, yard, and streets are under a foot or more of water, due to excessive new construction developments that all drain into this area of town. This is the only house that is affected.

So, there is nowhere for excess water to go during really heavy rains. Due to the crawlspace being flooded many times over the past 10 years, the floor joists are shot. The floors have sunk down approximately one inch and when you try and jack them up, the floor joists collapse.

I have several rentals and my son works with me. He thinks I should just donate the house to the city and walk away. I was wondering if it would be feasable to pour the crawl space full of concrete to eliminate the crawl space and turn it into a slab foundation.

This house is approximately 1500 sq. feet and in great shape other then the floors.

  • your son is a wise man.
    – Ast Pace
    Jan 14, 2017 at 4:13

2 Answers 2


You certainly wouldn't pour dozens of yards of concrete in there. You'd remove the organic soil, fill it with sand, and pour a 4" slab on that after setting up the plumbing.

Alternatively, look at an internal drain tile loop, along with some ventilation. It would be fairly easy to trench in perforated and socked pipe inside the footing. The tough part would be getting through or under the footing.

  • Thank you for responding ......what would be the difference between filing with sand, or gravel before pouring a slab ? Also how would you support the walls if the floor joists need to be removed befor pouring concrete ? Or just leave the floor joists ?
    – KW21
    Apr 2, 2016 at 3:43
  • Please don't ask new questions in comments. Whether to use sand or gravel is a question for someone looking at your project in person. Often sand requires less compaction, but there are other factors. The weight of the structure will probably prevent the foundation wall from moving, but again, I'm not there.
    – isherwood
    Apr 2, 2016 at 15:18

First, re-grade & sculpt the yard as well as possible. Mound-up the front to create a dam effect & also create relief gullies along the house sides so surface water can flow readily around the house & can't sit to soak-in. Like, your front door may be a step up from the front walkway, you'd re-grade up to the door threshold & do a flush new walkway. And/or, install a high street curb. And/or, install a Storm Drain with surrounding catch basin or swale that the Town won't...on your property with a large diameter pipe to the back yard or wherever.

Otherwise, I'd have to say totally fill-in the crawlspace & only do gravel & the concrete slab within the joist height. Get the house out of the new "water table" entirely. You won't have joists to ever get damaged again & you'll have an easily replaceable floating wood floor as the only future concern. This would also address any Radon issues you may have.

Of course, institute whatever permanent technologies of waterproofing that you can. Ranging from jacking up the whole house & down to digging out the foundation to install waterproof membrane or thick plastic sheeting that's used for cheap shower & tub surrounds. Protects the foundation from rotting out due to future saturation. Concrete's great, but it isn't indestructible.

Personally, I'd stay away from any Gravel-Based or Landscape Fabric systems or assemblies, they just clog quite quickly & become completely worthless wastes of money & effort. So, no Drain Tiles, French Drains (unless they're true French Drains being an open gutter catch connected to solid exit piping), no Sump Pumps & no interior "Water Management" nonsense.

  • Thank you for your response ..... I have already built up the dirt around the foundation...... Problem is the whole yard and beyond gets flooded even the street and the street has to be closed down ....I do like your idea of filling crawl space with gravel and only pourind
    – KW21
    Apr 2, 2016 at 3:13
  • And pouring just a slab....... Any suggestions on how to pour a slab on existing house? Can I pour a slab with current floor in place ? If not how can I support the house while tearing out the floors and joists? By the way the main support beam may be rotted also
    – KW21
    Apr 2, 2016 at 3:19
  • Also I thought about raising the house one concrete block .....
    – KW21
    Apr 2, 2016 at 3:26
  • Do you think I can remove the flooring and subfloor and leave the current floor joists and pour a slab over existing joists? My concern is supporting the walls and house during the demo
    – KW21
    Apr 2, 2016 at 3:34
  • I meant dirt, but if the crawlspace's bottom is level with the yard then a deep tamped bed of gravel for flow-through would be far better. You'll need foundation inlet & outlet holes. Raising the place needs a Lifting Company. But, you can do a filling of the joist & rim joist dimension. Do it piecemeal, room by room. Begin with dry wedge-in & shim-on block(s) between every other joist. Remove floor & joists, aluminum tape bottom & sides of stud wall's sill, fill the voids with mortar-in block(s) & big long lag bolts, go back to 3-step your dry block areas, crawlspace gravel fill-up & slab.
    – Iggy
    Apr 2, 2016 at 8:31

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