What is a better foundation, concrete block or poured?

[canfossi]

I am in the process of getting quotes for a slab on grade foundation with 4' high frost walls for my 2 storey home, as I am in Ontario and it gets cold in winter here. Which is the best concrete block or poured or does it matter? Thanks Chris

[moopups]

Check out a poured footer with mortared blocks up to the floor level. There are blocks known here as 'lientals', they feature a missing 1/4th, running length wise. This is the cap row of the mortared blocks with the missing section turned inwards. This way when the floor is poured the hollow centers become part of the pour. This is known as monolithic pouring and is rather strong. All added weight of the walls are placed directly on the 4 foot underground footer, which is placed on undisturbed earth as to your local building code.

[Farmer Willy]

Best wall would be reinforced poured concrete. cheapest might be the block. Depending on the crew the wall could be formed and poured in a day, another day to strip the forms and backfill. Both would work, concrete would resist lateral shifting better (assuming a keyed footer).

[Ramblin Wreck]

A properly constructed poured wall will last longer than a properly constructed block wall. Both will way outlast the original owner/builder. In our area, cinder block walls are less expensive, but most are now using poured walls...due to building codes I think.

[michiganfarmer]

I think most of the posters are correct that concrete is stronger and more durable. I like block because I can do it myself, ans I can always drop some re-rod in the block and poor all the cores. I cant, however, make my own concrete forms for walls.

[ET1 SS]

One year ago I had to make the same decision.

an eight inch thick concrete wall, is an eight inch thick concrete wall. Whether it is poured from a truck into a form, or if it is stacked blocks and filled with concrete. Either way will produce a 8 inch thick solid wall. by surfing manufacturers websites AND code, both are considered absolutely the same. both types of eight inch thick concrete walls are still eight inch thick concrete walls.

Either method you should use lots of rebar. Either method allows you to use lots of rebar. [one bar per foot, both horizontally and vertically]

Pouring can be done in three days. day 1 the trench is opened, and the forms are set. Day 2 it is poured. Day 3 the forms are pulled and backfilled.

I got estimates for doing both. Two estimates for contractors to pour the footing, and one estimate for the concrete blocks, the concrete to fill the blocks and the rebar all to do the labor all myself [all summer long]. then I got a third estimate, and I told them what my estimate was for building the foundation myself, the third foundation contractor matched the estimate for me doing it myself.

[Selena]

Not sure how homeowner's insurance works in Ontario but during my recent experience with switching insurers, I was asked did I have a cement (poured) rectangular foundation. Will cost more to pour but may cost less to insure.

[Thoughthound]

I asked the same question of my father in law (retired master carpenter).

He said, in his experience, both are strong enough, but the monolithic pour was better at keeping moisture out of the basement.

[Jennifer Brewer]

Originally Posted by Thoughthound

I asked the same question of my father in law (retired master carpenter).

He said, in his experience, both are strong enough, but the monolithic pour was better at keeping moisture out of the basement.

And here is where the true difference lies.

Maybe not today, maybe not tomorrow, but a block foundation, given access to water, will leak. those blocks are porous.

[ET1 SS]

Originally Posted by Jennifer Brewer

And here is where the true difference lies.

Maybe not today, maybe not tomorrow, but a block foundation, given access to water, will leak. those blocks are porous.

Those blocks are made of concrete, and then filled with concrete giving a solid concrete wall.

Any concrete wall foundation in the ground should be coated with something to make it water-proof. My foundation I coated with tar and a layer of Styrofoam sheets before it was backfilled. and as we backfilled it, we made a french-drain around the foundation [a 12 foot wide sheet of felt, wrapped around a layer of stone and a 4 inch perforated drain pipe, and then more stone over the top of the drain pipe, and finally the sides of the felt were wrapped over it like a big burrito, right up against the foundation wall styrofoam].

Unless your poured foundation wall is thicker then 8 inches, then it is still a 8 inch concrete wall just as a concrete block wall will be. both having the same amount of rebar in them. and both should have water-proofing on the outside.

concrete is porous as is concrete.

whether some of that concrete was first poured into blocks and later stacked and filled with more concrete; or if it was all poured at the same time. concrete is still concrete.

[uncle Will in In.]

If you pour an 8' foundation and have a full basement, you will add greatly to the quality of your house. Also greatly improve and ease the heating and plumbing for the house. You are right, it increases the cost quite a bit. With a full basement you could get by with a smaller house. Come to think of it nobody asked me did they. Sorry

[Wildtim]

Check local codes, around here most municipalities won't allow block foundations anymore.

Block is weaker, not when dealing with vertical load, but when exposed to lateral force it doesn't hold as well. To many seams. In other words with either your house will stay standing but with block you are more likely to get cracking at the morter joints, even in filled rebared block, that may admit more water than a solid one piece wall.

[Shadow]

Pour concrete, no matter how wellyou build the house if the foundation ever has a problem of any kind the house will follow, This is not the place to save money.

[Beeman]

There is no possible way that block can be as strong as continuous pour of concrete. First off block generally are lightweight so they are not the same concrete you would pour. The joints of the block are mortar mix, not concete, so that would be the weaksest point and where block walls have the tendency to crack.
I didn't think block met building codes fo most northern areas.

[Farmer Willy]

As expressed by others the block and poured walls are not the same. The block wall would be composed of 3 different materials, granted all are masonry, but all three are of a different composition. Yes, you can fill the blocks with concrete, it will be a stronger wall for the effort, but you will need to vibrated every core if you expected them to be grouted completely, otherwise anticipate it to be honeycombed inside. You can reinforce the wall horizontally with lath, but unless you notch the block or use very thick mortar joints you won't have the horizontal steel that you can use in the poured wall. All this being said, will block work? Of course it will work. Is it best? Not really. It probably is cheapest, can be done at your own pace. Check out your local building codes to see if it is acceptable. Either way insulate the slab.

[Ross]

The name completely escapes me but the solid poured concrete walls made from styrofoam forms so its insulated inside and out as it's poured are probably your best option here. You don't say where in Ontario, so that "cold" reference can mean anything from wimpy wet SWOntario cold to respectable E Ont cold to why on earth do you live there, N Ont cold! No matter poured is best, and I still prefer the tar coating and sand back fill, over that plastic "bubble" wrap and native soil back fill.

[ET1 SS]

Has anyone heard of 'ask the builder'?

http://www.askthebuilder.com/439_Pou...ck_Walls.shtml

Q.

What is the difference between concrete block and poured concrete foundation walls? Which one is better? The lot I am going to build upon has a seasonably high water table. Which of the wall systems would insure a dry basement? Diane J., Redwood Falls, MN

A.

DEAR DIANE: I think it might have been easier to answer a question such as: Is a glorious sunrise more beautiful than a magnificent sunset? The truth of the matter is that both building materials - concrete block and poured concrete - can yield superior foundation walls so long as they are installed correctly. All too often builders and sub-contractors fail to realize the limitations of certain masonry materials. When this happens, foundation failures are a common occurrence.


The first thing to realize is that concrete block is made from poured concrete. The primary ingredients in concrete block happen to be: Portland cement, gravel aggregate and sand. These are the same ingredients you would find in a poured concrete foundation. The only difference being the size of the gravel used in each application. Typically you will see gravel stones as large as three -quarter inch diameter in a poured concrete foundation. A concrete block may have gravel no larger than the size of a pea.


Poured concrete foundations are solid through and through. This happens by default as the plastic concrete flows from the ready mix trucks into the foundation forms. The typical concrete block foundation is not solid. The concrete blocks that are used to build block foundations, by their very nature, are hollow.


When concrete blocks are stacked on top of one another, you can look down through the center of the foundation. After the concrete blocks are laid, the voids can be filled with a cement-based mortar or poured concrete that contains small pea gravel. If the builder does this, then the filled concrete block walls are nearly identical to poured concrete walls.


But simply doing this is not enough to satisfy myself, code officials and structural engineers. Concrete and things made from concrete or cement tend to have fantastic compressive strength. Often it is measured in the thousands of pounds per square inch range. But the same material typically has only one-tenth the strength when you apply a tension or stretching force to it. Bending a poured concrete or concrete block wall creates tension. Backfilled soil against a wall produces tension as the soil pushes against the wall. Poor quality soil creates tension on a foundation as more and more weight is added to the foundation as the house is built.


You can strengthen poured concrete and concrete block walls by including reinforcing steel. Often you will see horizontal steel bars placed in the lower and upper sections of poured foundation walls. This steel often has a tensile strength of 40,000 pounds per square inch. This horizontal steel helps prevent vertical cracks should the foundation drop or heave. Horizontal wire fabric can also be placed in the mortar joints between layers of concrete block to achieve the same result in a concrete block wall.


Vertical reinforcing steel is also very important. This steel can be put in both a poured concrete foundation and a concrete block wall that will have the hollow voids filled with cement grout or pea gravel concrete. The reinforcing steel should be one-half inch in diameter and these rods should be connected to the poured concrete footer that the foundation rests upon. This steel should be placed every two feet on center.


Neither wall system will be waterproof. If you want a dry basement or crawlspace you must apply a foundation waterproofing system to the exterior of the foundation walls after they are built. In addition, a drain piping system needs to be at the base of the wall adjacent to the footer. This pipe is covered with two or three feet of washed gravel. The gravel is then covered with six inches of straw or a sheet of tar paper before dirt is placed over it. The straw and tar paper prevent silt from the fluffed up backfill dirt from clogging the gravel. The water that flows through the soil and makes it to the pipe is then drained to daylight if the house is built on a sloping lot. If the house is built on a level lot, the drain pipe often empties into a sump pit.

[Alex]

All we used are some big rocks with cement grout -- no problem.

The strength of the building, also depends on the structure. You can tell from looking at our freshly stained (first time in 34 years -- no stain before last year) Poplar log cabin that it is strong.

These huge logs vary from 10" to 22" diameter, are spiked with 12" steel spikes 6'-0" on center and alternating centers on each level. I drilled a hole 1/2 the log diameter at each spike and drove it into the lower log. At each notched corner I put 4 -- 12" spikes.

Sure the strongest is reinforced poured concrete. Reinforced concrete blocks are a second. But what do you need? But our cabin is not in an earthquake zone in northern BC. So, it's up to you -- depends on lots of things.

Good Luck,

Alex

[frugalville]

Good points each way. "Willy'... Good point about the 'modified monolithic pour'. That concrete that goes down in the brick would need to be vibrated 'well' to serve the intended effect. I called it modified, cause i was under the impression that a true monolithic pour is footers and slab at the same time... no cold seams.

Cold pour seams between trucks, pours, or block and concrete are not good.

Using the block and concrete to try to achieve 'nearly identical' wall as a poured one...

Builders today who use block probably are building for someone else. Ask someone who build their own house and you will probably get a different response.

Remember you can specify you wall pours, 3000-4000 psi strenght, fiberglass.. and so on.

Skip the extra few pieces of dental moulding, and treat yourself to a 10 inch pour. You deserve it.

Good luck.

[MississippiSlim]

If the blocks are filled with concret and rebar then the stresses will be the same on it as it will on concrete...it is still poured concrete. You can actually dry stack and fill voids and have the same strength. remeber, concrete is very strong in compression but weak in tension so the main thing is to have the proper rebar schedule no matter what you do. Also all blocks are not created equally. You have different fire hour ratings ......I would read up on construction there are some great books availabel as well as study your bulding code