Friday, June 19, 2015

More retaining walls

Welcome to our blog, Menfranco general blog,
and this post, More retaining walls
These retaining walls: 
Dear readers in this post, we are going to continue to talk about retaining walls, since there are a few things that we have not yet said, as you know different circumstances call for different solutions, so let us continue to talk about retaining walls.
You see, when the block of land that you own is steep it requires a lot of work to be done, if you want a small portion of your land flat, so that you can stand and enjoy whatever is there to enjoy and do whatever you would like to do in the open air.  See the photo here under, they have built a besser retaining wall with an indent in it, mainly to give extra strength to the block wall and also to put this concrete slab and use this indent with whatever they want to do next. Note that above this block wall there is another sleeper retaining wall, these sorts of things are very costly, and one should really plan it out before one starts, anyhow under below we are going to write about a Besser block retaining wall, first just a normal strong retaining wall and after that we are going to build a leaning Besser block wall, somehow similar to the hybrid rock wall. 

This is just one type of retaining wall that we are able to show you

Besser block retaining wall
Besser blocks retaining walls require a reinforced concrete foundation with steel starter bars placed exactly if possible in the centre of the hollow part of the block, when you look at the wall from the front or back, and if possible a bit close to the side where the pressure of the soil is going to be, but that could be asking too much from the concrete man and the steel fixers. So for a start a proper profile should be set in place before you can even concrete the foundations, or fix the steel in the foundation, because all measurements need be known and easily measured while working on it.
This is a very demanding job and it is not really a do it yourself job that is easy to do. So the name that I have given this article DIY retaining wall would not apply in this case, you see I apologise because I was forced to use DIY just to overcome the problem of the title that happens when we start a new article and find that the name we have chosen has already been taken.
When you build a retaining Besser block wall and you want the wall to be as strong as possible, you should start laying the first besser block with an open block, this block looks like a square C, and you lay it with the open side facing away from the bank that it is going to hold back when everything is done, the corners would be built with normal blocks and most of the walls are built with blocks that look like an H, so that it is easier to fill up with concrete, once the wall has been built. Now while the block layer is laying the blocks, he will have to lay some horizontal steel bars between the courses of blocks as specified, if there is a real plan and specifications, or just use common sense, or copy from the specifications of a similar job he has done before, the vertical steel bar will be inserted from the top before or while pouring concrete into the blocks.
Now the reason we need to use an open C shaped block the first course becomes obvious now, because it is necessary that before we fill up the blocks we remove the mortar that has fallen down at the bottom of the blocks while we were laying them, you see we really want a very solid base and we want the concrete to bind around the starter steel bars that we have laid in the foundation and this is the best way to make the retaining wall as strong as we can. Once that is done we can fix a plank against the openings and we are ready to pour the concrete in the wall. 
Here we have to mention that for this retaining wall we have not mentioned any drainage yet, so what happen to the water that seeps behind the wall needs to be worked out, you see sometimes when we build walls this strong usually there could be a reason that we do not want any water past the wall, perhaps it is part of a base of a house being built, so, for that reason we have not even left any weep holes in the wall, because there is going to be a drainage pipe laid behind the wall surrounded by gravel. The wall might also be treated with some special paints to water proof it.
This is just one type of blocks retaining wall and I am going to write about another type, where we lean the retaining walls towards the bank or future back fill that it is going to hold up, this is a large job that we did years ago in a yard of a new large home in Redhill a Brisbane suburb. We are going to write it here, just to show you another type of retaining wall and the many ways that can be built.

Redhill backyard problem
Years ago we worked on this part brick house in Redhill, we say part brick house because the top floor interior was made of timber and was a brick veneer, the base was solid bricks and blocks, it was a large house and the block of land had two street frontage. It was on a steep hill and the difference between the front and the back yard was a lot, but the two street frontages was good, because the house was being built on the higher part of the block of land and was nearly flat there and almost level with the road, so there were no problem there, but the back yard was very steep, in some places could have been up to 45 degrees. When we finished the brickwork on the house we were asked from the owner if we could build some retaining walls, because the backyard was useless as it was. So after discussing the financial part how he would pay us; we started to discuss how we could fix the back yard building block retaining walls, and so it was agreed that we had to lay these block retaining wall leaning a few degrees towards the bank and there was going to be concrete stairs on one side, so that the back could also be entered from the back street and so working together with the owner we did the following.
Because you cannot build a very high wall on the road boundary, first of all a section of about 4 feet wide (1.2 m) was dug and a foundation was poured, with starter steel bars as needed and the main wall was set about a meter from the road where the first retaining wall was to be build, this was the main foundation for a start, some of the small foundations and other adjustment we had to work out as the work progressed.
The decision was that we had to build the wall leaning towards the bank for extra strength; you see when building retaining walls the weight of the retaining wall together with the weight of the foundation should be more than the weight that the backfill could move, if it is possible that you could build a very strong monolithic wall and foundation together this could be the best solution, in this case it could never be possible, because the job was too big, beside that you need to have a very wide and heavy foundation and also a very strong bond between the foundation and the wall, since this bond between the foundation and the wall is the weakest point unless it is concrete and poured together, but we were using blocks to build the wall, therefore it had this weakness at the bottom of the wall, so by leaning the wall towards the bank, the weight of the wall itself would be the first point or resistance.
Now, how much we should lean the wall was left to us block layers, because we for sure would have some problems, and there were several problems to overcome here; the very first problem is that if you have to return the corners it cannot be done, of course we had corners on the boundaries of the joining block of land, so we had to think how to overcome this drawback first of all, for this it was decided that we should not build a return corner as usual, we should treat them as separate, but we would place a corner steel rod every course, instead of every second course, as in the wall itself.
There was also the possibly that while we were building it, if we leant it too much it could fall on the inside, while we were building it, so we had to strike a balance. Knowing that this first wall was going to be no more than 3 meters high, we worked out that if we leant the wall 5 centimetre per meter, the top of the wall was going to be about 15 centimetre back from the perpendicular, the blocks were 19 centimetre wide and it would be okay, as once the wall was built it could stay up on its own without falling inside, but while we were building we should be very careful not to apply any extra weight on the leaning wall, just for fear that this could happen we added a couple of block piers behind the wall, this would not only make the wall safe for us while we were building it, but it also would make the whole wall stronger. 
Anyhow we built this block wall placed the reinforcing rods in place, we also built some concrete steps on one side of it, so that if you happened to be on the back road you would be able to go to the house, the ready mix truck came and the wall was filled with concrete and that was the first stage finished. We had to wait for this wall to become strong before we could backfill it, and then we would come back to built another retaining wall half way up the backyard to finish the job.
Dear readers, be warned that this type of work can only done from very experienced block layers, as it breaks all the rules in the building trade, but we did it and it worked. 

I may have to come back one day when I feel that there is more to say, but for the time being I believe that this article is becoming too long, so see you in our next post that we are going to call, Mix your own cement. 
This is: 
Menfranco general blog, 
More retaining walls
Next time with, Mix your own cement
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