Saturday, February 11, 2012

The main types of foundation walls


The different materials you can build with to make the foundation walls of your custom home.
Block Walls:
Block walls have been around for a long time. They are made of cement and are hollow on the inside. Block walls are constructed by placing one block on top of the other, staggering the block ½ a width every row as they are laid. You mortar between each block as you lay them and then pour concrete down the holes to stabilize it. The blocks are hollow making them lighter to lift and place, it also makes them cheaper to buy. Block walls can be cheaper depending on your labour rate, but with today’s labour rate ever climbing block walls have become the same price as other types of foundation walls.
Some drawbacks of block walls are that they are only stabile when they have pressure from above straight down. If you have a large amount of pressure on one side of it like water soaked ground without support on the other side of the foundation the wall will fail and collapse. Insulation has to be added to the inside of the wall to keep heat in the basement. If the waterproofing fails on the outside of the foundation, water will penetrate the block and fill the cavity in the block. Overtime the water will make its way up to the wood rim joist where it will eventually rot it out.
Block walls that are above grade have to be parged to ensure water does not penetrate the block and cause damage; also it is to give it that finished look. If water is allowed to penetrate the block and then it freezes it will cause major damage with cracking and shifting in the wall.
Concrete Poured Walls:
Concrete poured walls are poured concrete into wood forms that are placed on top of the footings. Usually forms are made of plywood with 2x4’s as backers and reinforcement. Once the forms are assembled to the desired height and width then the concrete is poured into the forms and allowed to set. Once the concrete is dry, the wood forms are stripped away and what you have left is smooth concrete walls. Concrete can be more expensive then block walls but it is less labour intensive so it can end up being the same cost as a block walls. The difference with a poured concrete wall is that it has strength to take pressure from all sides. Concrete walls are good at withstanding large loads vertically and horizontally. Unlike block walls, concrete walls do not need to be parged when they are above grade, they are already finished.
Poured concrete walls need to have insulation placed on the inside of the walls.
Concrete walls can be easily engineered to act as retaining walls, take extremely large loads and can be shaped into curves or rounds.
Concrete walls when properly engineered can withstand shifting, cracking and poor soil conditions.

Insulated Concrete Forms:
Insulated Concrete Forms or ICF are two pieces of polystyrene that vary in length and height. They are held together with plastic webs making them into blocks that have a hollow core that is filled with concrete varying in sizes from 4” to 12”. They are installed like block walls but do not require mortar to hold stay together. Once the walls are constructed, with rebar as reinforcement inside the forms and the braces in place, then concrete is poured down from the top of the wall. A vibrator is used to make sure that the concrete makes it around all the webs that hold the wall together. Once the concrete is dry you simply remove the bracing that was put in place to keep the walls straight. The insulation stays in place.
ICF blocks are light and easy to manipulate while building the foundation. The labour is cheaper then block walls but slightly more the concrete walls. The ICF blocks are the expensive part; ICF foundations are the most expensive way to construct a foundation. ICF walls are as strong as a poured concrete wall vertically and horizontally.
What you get when you build an ICF wall is a pre-insulated foundation wall that has an average insulation value of R-22, but since there is no air transfer the wall performs like an insulated R-40. Even if you insulated other foundation walls (when building with concrete or block) you would never be able to achieve this level of performance. ICF walls give your basement that feeling of being above grade with the basement being warm and damp free.
You have to parge the ICF block that shows above grade for finishing purposes and to protect the ICF block against UV rays that will erode the foam on the outside overtime.
All three of these main options have to be waterproofed below grade; the waterproofing for all three of them is pretty much the same. The only thing you can’t do with an ICF foundation is use tar to coat the walls for waterproofing. If you are having a house built, you should never allow a builder to use tar to waterproof your foundation.
                These are the main three options you have when you are building a custom home, there are other options but these are the most popular and the most widely used by architects and contractors. All these foundations must be placed on top of footings and inspected by the building inspector before they are filled with concrete.
If you are looking for a price on a foundation, or a whole custom home feel free to email me at robabbott@villagebuilders.ca or visit our website at villagebuilders.ca
Rob Abbott
Operations Manager
Village Builders Inc. 

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