DIY Concrete Porch.
DIY Concrete Porch.
Hello.
Today we will talk about building a porch like this one, mostly from concrete, with a total cost of about $170.
The estimate is attached at the end of the video.
The choice of materials was determined by a limited budget, and the porch design had to meet several criteria at once:
• This is the ability to build a porch with one person;
• The absence of equipment on the site, such as a mixer or even a concrete mixer;
• and High maintainability and availability of replaceable parts.
The limited budget (in my case) plays a key role and in practice results in a number of disadvantages that you need to know about even before choosing the type of design.
Disadvantage 1. The depth of the foundation.
Usually, a trench for arranging the foundation is dug to a mark below the level of soil freezing.
In my region, this is 80 cm, and somewhere around 2 m.
It is generally accepted that at such a depth the soil under the foundation will not freeze, which means it will not increase in volume and will not lift the concrete.
Sometimes, however, the soil on the sides of such a foundation can also freeze and move the monolith a little, but this is rather an exception.
In the vast majority of cases, this is an excellent solution for a cold climate.
In my case, when arranging the porch, the existing concrete blind area around the house and a gravel-sand cushion act as a foundation system.
To do this, I simply removed the fertile soil layer, in my case it is 25 cm.
I additionally compacted the bottom of the trench of the appropriate depth with a layer of crushed stone and laid the remains of agrofibre with a density of 300 g / m2.
Then I filled the trench with gravel crushed stone of a fraction of 20-40 mm and compacted it well.
I filled the pores between the stones with sand, poured water over them, left it like that for a couple of days and compacted everything again.
But what about frost heaving forces?
Yes, they will be there, but what effect will they have?
I admit that the structure will locally be lifted by a couple of cm, but as soon as the frosts recede, the porch will return to its previous levels.
Unlike a concrete foundation, which, even if it lifts the edge of the building, will almost never lower it to its previous levels after a thaw.
A couple of such winters with an unsuccessful classic foundation under the porch and you will no longer be able to open the door from the house.
... On top of the gravel and sand cushion, I lay a wall of concrete blocks.
To prevent local movements from pushing the wall apart with frost heaving, I put reinforcement with a diameter of 12 mm at each level.
I am not against possible thin cracks, since their size will be restrained by the reinforcement.
Disadvantage 2. Waterproofing of the porch.
...Or rather, its complete absence.
You probably noticed that when pouring the upper concrete slab, I deliberately left part of the old porch.
Firstly, there is very strong concrete there, which perfectly bonded the fragments of a typical flight of stairs from the Soviet Union.
I realized that this pile is very difficult to destroy when I poured the concrete blind area.
In addition, the structure, being in the open air for 20 years, perfectly resisted the forces of frost heaving and looked more alive than all the living.
I decided that it was stupid to remove such a stable installation and replace it with a new one, which is unknown how it will behave during freezing.
It was decided to add a new slab to the existing monument.
Naturally, I did not perform waterproofing between the old and new concrete, for better adhesion.
But is it really necessary?
After all, concrete itself is not afraid of moisture.
I do not plan to cover the concrete slab with tiles, contact with wood and other hydrophobic coatings is also excluded.
The metal corners on the steps may be damaged, but they will last for a couple of decades, and they can be replaced in 1 hour.
In addition, in the future, it is planned to build a canopy over the porch ...
... The most difficult task was to make a collapsible formwork for the upper slab from the remains of old boards.
The upper slab has dimensions of 105x222 cm, with a thickness of only 5 cm.
Old films were laid to prevent the leakage of cement milk.
I used reinforcement with a diameter of 12 mm.
I poured concrete for the slab from M500 cement, washed river sand and crushed gravel of 5-20 mm fraction in a ratio of 3:4:5.
I tried to pour no more than 0.5 parts of water from each part of cement. After pouring the slab, I iron it and cover it with a film for 28 days, so that the concrete reaches the calculated strength.
Ironing concrete is when a layer of dry cement is poured over the fresh fill, followed by grouting.
There are different opinions on the Internet regarding ironing.
Many complain that this super-strong top layer peels off from the main massif.
Keep this in mind!
Then, instead of a welded frame