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willkess
Filling in sunken area in workshop.
willkess

I just bought a home in Santa Fe, NM and am in the process of converting a room into a workshop.

The floor is slab on grade and looks like it has been in place for at least 20 years. In the middle of the room there is a 3.5" step down to a lower slab.

I was thinking about pouring concrete to match the level of the higher slab and then use a self leveling finish across the whole room.

My plan is to put down tar paper so the new slab doesn't bond with the old and use re-mesh as my reinforcing. The articles I have read also recommend using a concrete mix which is sand and cement and no coarse aggregate. It looks like it will take about 24 cu. ft to accomplish the project.

I think I have thought it through pretty well but I want to put it out there and see if anyone has advice or recommends doing the project a different way.

Thank you in advance,

Will

dj1
Re: Filling in sunken area in workshop.
dj1

It looks like you got all your ducks in a row...good luck.

Send pics of the before, in process and after, if you can. Just load them on photobucket and post the link here.

ed21
Re: Filling in sunken area in workshop.
ed21

I don't see why you wouldn't want the slabs to bond. No need for tar paper. When joining slabs usually drilling and inserting short lengths of rebar or bolts to make sure the slabs don't move is done. Reinforcing probably isn't needed, but mesh may help to prevent shrinkage cracks.

dj1
Re: Filling in sunken area in workshop.
dj1

ed,

I think he is talking about a small "pit" in the middle of the room. Very simple.

He mentioned that some say to use a mix of sand and cement only. For a workshop, I would add gravel to the mix.

ed21
Re: Filling in sunken area in workshop.
ed21

That's what I implied I thought. Reinforcing not really required for filling a small pit even though some wwf in the new slab wouldn't hurt. Securing the perimeter shouldn't be required. Aggregate won't hurt as long as it's floated.
On second reading of first post I see that it looked like I said to secure the perimeter. Not what I meant to say.
I was also questioning the need for a bond breaker like the tar paper mentioned.

willkess
Re: Filling in sunken area in workshop.
willkess

Ideas on using less concrete. The compressive strength does not have to be very high.

Here's what I was thinking

1. Add an inch or two of gravel to get my slab closer to 2.5" thick.
2. Use Sakrete Maximizer to get a higher volume per weight.

Here's a pic of the fill area.

Jack
Re: Filling in sunken area in workshop.
Jack

You don't say what kind of workshop you are putting. If it is going to be a wood working shop I would consider running 2X's and putting down a wood floor. Wodd is much easier on the feet and tools.

Jack

Mastercarpentry
Re: Filling in sunken area in workshop.
Mastercarpentry

You can use a standard concrete mix for this, 2500# (sackcrete) will do. What you want to do first is what will matter the most! Etch the lower floor with muratic acid diluted to 50%- ventilate well during this process as the fumes will be mean! Doesn't take a lot, just get it all wet. Let it sit 15 minutes. Normally you'd then rinse with a hose, but if that can't be done you can spray lightly with clean water and use old towels to soak up the left-over acid. Do this well, you may want to apply the water and towels 3-4 times to be sure you get it all. Rubber gloves' old pants that you will throw away, and rubber knee pads are a must, eye and face protection also a good idea.

Once the floor is completely dry, liberally apply a concrete bonding agent such as "Acryl 6o" with a brush or roller. Give it 10-15 minutes to penetrate then pour the floor and finish to suit you. With a 3 1/2" concrete thickness the floor should be fine even if it doesn't bond well, but the better the bond the better the floor will be in the long run. It's not good to go much thinner so I wouldn't use a 'fill' to reduce concrete costs. Cover the finished floor with plastic for a few days to slow the curing and help avoid shrinkage cracking. Don't drill or drive fasteners into the new floor for at least a couple weeks- a month is much better. If you want to seal it, that needs a week's time after the plastic is removed. This will give you a 'forever' floor and no problems in the future.

Phil

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