Customer has a house about 30 YO with plain concrete slab for a patio in back. The concrete “cracked” (whatever that means) so she had a wood deck built on top of the concrete. I don’t thinik they used PT wood, as it is in pretty bad shape, and now she wants to have the wood deck removed, and the old concrete slab removed, and replaced with a brick paver patio.
I have not seen the old concrete slab yet. Here’s the question: Assuming the concrete is not broken up, and still relatively flat, can I use that as a base for the bricks, or should I remove it?
Replies
You just need to determine if it is a single cosmetic crack or if the soils are still likely to be moving. What soil is under the slab and if there is steel in it.
If the slab is sound, yes.
But your rep is on the line. If it moves and cracks the new grout joints or unsettles the bond brick to slab then she won't love you any more.
How much elevation do you have availabe? You might be able to pour over it with another thin float and wire.
After you determine the cause of the crack and that is corrected, you may be able to level a sand base and lay the paver bricks on top of the patio, which would be very easy to do after you figure out the edging detail.
I was in a similar situation that turned out to be caused by a cracked gutter drain tile that ran underneath the slab.
There were other problems caused by this, such as water seeping through a basement window well and into the basement.
As soon as we moved in the house the gutter downpipe was cut off and diverted onto a hose and away from the house.
After contemplating several options, I ended up sledgehammering and jackhammering away the 12x16 slab and dry laid a 12x30 paver brick patio in a 90-deg herringbone pattern.
The dirt base was slope away from the house and plate compacted.
Plastic was laid, then gravel was plate compacted.
Landscape fabric and then sand and brick.
Ended up using about 5 tons of gravel to raise up one end of the patio to near level for the brick paving.
We went with brick mainly for possible future expansion of the house out onto the same area that would involve excavating down to the basement level. Take up the bricks, and already have sand and gravel for mixing concrete, etc.
Alan
I hadn't even thought about loose laid over sand or stone dust. I've laid then in mortar beds on a slab. The layer of sand would be more forgiving if there is slight slab movement.Excellence is its own reward!
I wish I could have mortared the bricks, which would have looked better since our patio is butted up to the house.
Although sand base is forgiving and easier to correct problems down the road, if the patio is butted up to the house, sand can be tracked into the house because whenever it rains sand is splashed out of the joints.
An occasional push brooming the sand back into the cracks and off the surface is part of the routine.
Also, weeds can pop up between the cracks.
Can't do much about seeds that land on top of the surface and germinate.
We do have a covered kitchen porch that steps up from the patio that is a good buffer to take care of dirt/sand getting tracked into the house.
I can see many advantages to a mortared patio but I wanted to be able to reuse the bricks if the patio had to be removed.
However, with a pergola that covers the entire area before the bricks were laid, excavating down to the basement may never happen....
Sounds like you're not sealing every couple of years. The sealer is like a wax: it seals the concrete pavers to protect them from fading and from any stains penetrating, it also forms a little bond coat over the joint sand which prevents both weeds and wash-outs..
Phill Giles
The Unionville Woodwright
Unionville, Ontario
Sealer ?
No such thing was mentioned anywhere while I was researching paving options.
You mention "concrete" pavers - I used brick.
One thing I wish I had used instead of sand is stone dust, which in hindsight compacts and holds together better and less likely to splash out from between the bricks.
I'll look into this sealer but besides the occasional sweeping, maintenanne was not what I had in mind.
I guess there is no such thing as maintenance free.
Thanks for mentioning the sealer.
Alan
Real brick, as in 'build a wall' bricks ? We get three types of "bricks": real clay and concrete architectural bricks, and concrete pavers. Virtually all "brick" driveways and patios in my area are made with concrete pavers. Some DIY patios are done with concrete architectural bricks. I haven't seen clay pavers in 20 years, but that doesn't mean there aren't any around. PS: I just had my driveway done last week: concrete pavers that look like cobblestones; interesting pattern, three colours and three different paver sizes.
Here are some random sites with care instructions for "brick" paving
http://www.sealpro.com/pavers.htm
http://www.unilock.com/
http://www.aldonchem.com/mt-pavers.htm
http://www.goldenlook.com/sealer.htm
http://www.menco.com/Concretesealers.htm
http://uni-groupusa.org/.
Phill Giles
The Unionville Woodwright
Unionville, Ontario
Thanks for the reference links !
As far as I know, the paver bricks we used are "bricks" made for paving. They don't appear to be a concrete product.
We get ours from Pine Hall Brick, which is based in North Carolina and is an advertiser in FH.
They offer two grades - heavier duty one is for areas where vehicles such as dump trucks are anticipated in the future.
Otherwise, the regular pavers are sufficient for normal car traffic.
Here is the page showing the "bricks" we used.
It's the red English Edge and we laid them in a 90-deg herringbone.
http://www.pinehallbrick.com/pages/pg_paver.htm
I do notice concrete pavers are more popular in California and many variations of them in Canada.
In our town, many folks are beginning to use concrete grass pavers each weighing about 40-lbs. Offers good drainage and looks great with occasionally mowed grass. For our driveway we may use that.
Alan
Phill, Just a note for your information. Clay brick pavers are very common in my part of the world (North Carolina). There are miles of sidewalks paved in red brick pavers on both the University of North Carolina and the N.C. State campuses. I've done numerous residential jobs in (clay) brick pavers. These jobs have included brick floors inside as well as exterior paving. Some of my projects have consisted of fully mortared brick over a concrete slab; other have been set in stone screenings with no mortar joints. Brick pavers are different than face brick and must meet a separate set of ASTM standards.
'preciate the advice. She wants the new patio tto be the same size and shape as the old one, about 14x16'. Location is south Texas, frost depth is about 1/4" (we had to scrape frost off the windshield twice last winter), ground is predominantly limestone a few inches down. Diging is a real chore here. I was considering a sand cushion on top of the old slab with loose bricks. What the hey...I'll give her a quote to do it either way.
Yes, I read through the site given on clay pavers. They appear to be popular in the South. We're almost totally concrete here. Says in the literature that you have to be more careful about staining, cleaning, and sealing the clay than the concrete, but that the maintence is important for either system..
Phill Giles
The Unionville Woodwright
Unionville, Ontario
And the fellows who repair and maintain those sidewalks in Chapel Hill are an amazing and skilled bunch of people. Hopefully, their skills are being passed along. Many of them were getting quite "venerable," last time I watched them work.
Two years after we rented our house, as we were preparing to buy it, the home inspector pointed out that the deck porch we were using seemed to be causing water damage in the basement. Sure enough, a little sleuthing and the removal of a few boards revealed that the deck was built over a concrete slab, and heavy rubber or plastic over top of the concrete. The slab was draining straight into the corner of the basement, one inch gradient over eight feet. We repoured over the slab, and strongly considered the concrete paver in sand base over top of that."I don't know what you could say about a day in which you have seen four beautiful sunsets." --John Glenn
Theodora, I'm curious as to why you would choose concrete pavers over brick pavers. In this area, they're about the same price. Do you prefer the looks of concrete pavers or are you under the impression that they are more durable? If installed properly, either of these materials should be good for a lifetime.
We never got so far as to make a decision between the two. I would have liked either, and as a southerner, I would have especially liked the brick. On the other hand, given my grey and white Cape Cod, some of the color mixes you can get in the concrete pavers and some of the shapes, cobblestone types, would have been attractive. I probably would have placed aesthetic considerations first, and then looked at other parameters. In particular, the thickness of the material, given that raising the concrete brought it up way higher, and I don't know about clearance under the door. That probably would have dictated stamped concrete. We never got around to doing the project. I'm in SE Ohio now, Chapel Hill is home territory. Where I live now is clay soil, and we are certainly famous for our pottery, but I don't think brick is a big deal here. I'll have to look up why or why not. It's certainly not the default siding/sheathing material."I don't know what you could say about a day in which you have seen four beautiful sunsets." --John Glenn
"I haven't seen clay pavers in 20 years, but that doesn't mean there aren't any around."
Funny how some times information pops up on here . Let me give you some.
In the hills of Arkansas , the soil is red clay and rock . We cuss it for not growing certain things. Many farmers have gone broke . The well water has too many minerals ,including iron, which comes from red clay. It packs well, giving our foundations stability. This is the place clay brick and pavers come from. Acme Brick company , is a major factory plant that employs many here . So clay pavers are a part of our life here every day. Seems that their distrubution needs to be improved .
Tim Mooney
Stone dust compacts better but will still track into the house and it is nastier to clean up when it does. Sand can just sweep or vacumn up. Stone dust needs a wet wipe to get it. Sealer doesn't help too much with either, just with mortar, IMOExcellence is its own reward!
And you are so right about rock dust as we have those plants also. We have flag stone here and the dust used to be given away until they found out how well it packed . For several years we used it instead of sand under concrete house pours.
Anyway , while it was free for the taking , many people used it on their driveways in the country. We hauled in sb2 which is crushed stone , and then over laid it with rock dust . Rock dust acts as a cement when water hits it , and becomes very hard . Our best compactor we have here. Problem is this ; It tracks in on the carpet and stays . Between rock dust and red clay , carpet here only lasts a few years under normal conditions. Seems the rock dust cements to the carpet when it gets wet and clogs , not turning loose freely, as you descriped. The red clay has acid in it , therefore discoloring fabrics. Rock dust is a major problem being brought into homes here . Keeps the carpet layers very busy. Seems there is always a negative to a plus.
Rock dust would be the choice to be laid under those brick , over a cracked patio. Rock dust instead of sand in a pour is very very strong . We did a lot of experimenting with it while it was free. Now its higher than sand.
Tim Mooney
If you decide to keep the slab, and your work extends beyond the slab. Make sure you have compacted and prepared the adjoining soil to keep up with the slab. Having part of your patio submerge below the slab will cause unsightly dips and bumps. Essentially the slab will show through so to say.
Get rid of the slab and any potential problems with it will be out of the picture. I had the same situation (deck over concrete) in my house when I bought it. Tore down the deck, broke up & hauled out the concrete slabs, dug down 8" min. to clay, placed 6" of well graded stone (3/4" minus) compacted and 2" of crushed limestone screenings compacted. Set the concrete paver bicks on that. Five years later, no problems.
Doing it right the first time . . .
Eric
If you decide to pull the slab out, and if there's access to the slab that is at least 6' wide, it might be worth a call to the local rental yard. There is a set of concrete shears you can mount on a compact excavator which will make short work of concrete structures less than 15'' thick, rebar and all.
As for tracking sand, I don't think I've ever had a problem with that. I've only used ASTM plaster sand, maybe that's why, I don't know. Maybe keeping the brick horizontally retrained so they stay tight is helping, too.
Anybody have any thoughts on minimum sand thickness? I haven't tried it yet but I'm thinking about compacting a few inches of crusher fines (rock dust isn't cheap here either) and then using a thinner layer of sand on the next brick patio. Seems like the job ought to go faster and stay looking good longer that way.
DRC