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Guide – prepare and seal the concrete retaining wall

The following is a short list of products that are similar to those we used to prepare and seal the concrete retaining wall.

The list is very basic – Sealant, Stiff bristle brushes to clean the walls, and different types of paint brushes and rollers to apply sealant to the concrete sleepers.

Preparation – Scrub Brushes

Get the cheapest possible stiff bristle brushes you can find. The bristles need to be strong enough to scrub off any dirt away from the concrete sleepers. This will help with getting a better outcome from sealing the wall. If you try to seal over a dirty wall, it will not absorb and cover the wall properly meaning you may have to re-seal earlier than expected.

Heavy Duty Scrub Brush

Concrete Sealant

Concrete sealant comes in three finishes – Gloss, semi-gloss and clear. We selected semi-gloss which gives a slightly wet look without being overly shiny. We used about 50L of sealant for our concrete retaining wall. What was surprising is how much sealant gets absorbed into the concrete before you get to a point where you start covering the surface – you will need more than you think.

 

EnduraSeal 100% Acrylic “Wet Look” Semi Gloss Concrete Sealer Solvent Base – 5 Gallon

Paint Brushes and Rollers

Wide paint brushes 

We used a lot of wide paint brushes to cover our concrete retaining walls. These were great in getting the sealant into the corners and in between the stackstone pattern. Try to get something that is heavy duty as the course concrete and the chemicals in the sealant will destroy cheap brushes.

 

Heavy Duty 3 Piece(4,5,6 inch Professional Stain brush, Paint brush)

Paint Roller

If you have a flat surfaced concrete retaining wall, you can save yourself hours of effort by using paint rollers instead of brushes. We used rollers on the back side of the retaining wall. No need to spend a lot of money here as we got some of the cheapest ones available and they did the job.

 

You will need 2 coats

The instructions on all the sealants specify 2 coats, with about a 2 hour drying time in between coats. 

Our sleepers looked terrible with only 1 coat and its recommended to go with the manufacturers advice. Plus, you can see all the bits you missed and go over them again to make the wall look fantastic. I repeat – you will need more sealant then you first thought!

 

Part 2 – Retaining wall almost completed

Roughly two weeks after starting, the retaining wall is nearly completed! Another important milestone on the journey.

I cant state how difficult this job was, and its something that I definitely could never have done myself – certainly a job best left to professionals. The guys worked some big hours in the heat and moved literally tonnes of sleepers, posts and cement to get it done.

The retaining wall has finally given the front yard a bit of shape and some street appeal which it has never had before. Initial observations are that it is an extremely solid structure which will easily take the load of the soil which will be back-filled behind it. I have to catch up sealing the remainder of the wall but ill get to that when I have some free time.

The drainage system has been set behind the full length of wall and is now just awaiting drainage aggregate and back-fill (full details in this post).

Now with all that work completed, the next job will be to install the fence before moving onto the earthworks. 

Whats inside a Concrete Sleeper?

Have you ever wondered whats inside a concrete sleeper? I read that the Canberra Concrete Sleepers are reinforced with steel bars in the middle, but how can you tell if its really inside??? (not that I dont trust them!)

Well, during the work at our place, the landscapers had to cut a couple of sleepers and here is what we found inside:

Steel bars reinforcing the sleeper

There they are, two steel bars right thru the middle of the sleeper. Dense concrete surrounding it leaving little room for water to penetrate the sleeper
(Sealing the sleepers will protect it even more) . Colour is mixed right through the sleeper.

Above you can can see how the sealant was applied(needs another coat) and a cross section of the sleeper. So for all those that were curious to see whats inside a concrete sleeper, there you have it!

Part 2 – Good result from sealing the retaining wall

A few days after applying the sealer, it rained, and here is how it works to repel water away from the cement.

 

It really works, and the water beading on the surface is proof that it isnt soaking into the porous concrete.

 Hopefully this sealant will last a while and ill only have to re-coat the exposed surfaces every few years.

 

Part 2 – Retaining wall drainage

One of the more important, but often overlooked aspects of building a small retaining wall is the drainage. Without appropriate drainage, water will build up behind the wall causing erosion over time and loss of integrity.

  • Our landscapers are starting with a water proof liner on the back of the retaining wall
  • Then 200mm deep of drainage gravel will be installed immediately behind the retaining wall
  • Sitting on top of the drainage gravel will lie a 100mm slotted and socked PVC aggregate pipe which runs the full length of the retaining wall
  • The PVC aggregate pipe will be tested so that water will run down a small slope and exit near the end of our property close to drainage and natural ground run off
  • The aggregate pipe will then finally be covered with more drainage gravel before future soil backfill is delivered

This system is integral to protecting the integrity of the wall for years to come.

The diagram below is a rough example of what will be installed. Note, its not to scale but should have all of the key elements represented

 

Diagram of retaining wall drainage

Part 2 – Sealing the retaining wall

With the retaining wall being made from concrete, it should physically last for 20+ years without any worries or major maintenance required. 

However, a couple of minor issues related to the aesthetics do arise over time with coloured concrete, including:

  1. The colour starts to fade slightly
  2. Efflorescence caused by water and other material(fertilizer etc) can stain the wall

To prevent or reduce the occurrence of the above two issues, I sealed the wall with a concrete sealant purchased from the local hardware store.

 

To prepare, I used a strong bristle scrubbing brush to clean up the dirt that was stuck to the wall. After that was done, I gave all exposed areas two coats of the sealant, making sure I got to every little detail of the wall. I had to do most of it with a long bristle paint brush due to the nature of the patterned surface. I tried using a roller but it was just not getting to all the little nooks of the wall.

Needless to say it took a while, but I think it will be well worth it in the long run.

Here is what it looked like after applying the sealant. The sealant gives the wall a slightly wet look all year around and its not overly shiny. Here it is reflecting some of the light around sunset

 

I was able to apply the sealant while the landscapers were off site. With the weather being very hot and dry, the sealant dried in about 30 minutes allowing the second coat to be applied on the same day.

 

Part 2 – Its starting to take shape

It has been a week or so since starting this second job, and the guys have really got a lot done in a short period of time.

They are almost at the stage where the majority of the sleepers are set in place, and the drainage pipes can be dug in and installed.

The focus of the next few days is to finish the retaining wall and drainage so that they can move on to the framing of the fence.

 

Nice sunset

Got home in time to witness this beautiful scene from our backyard this afternoon. Nice way to end the day!

 

Part 2 – Some good early progress

A few more posts have gone in, which means that they have been installed all the way to around the front of the house.

They have also set some sleepers in place before levelling out and cementing the posts(next few days).

Each one of the sleepers weigh 45KG so its a bit of an effort to get so many set in such a short period of time. Great work so far.

 

Part 2 – The goodies have arrived

Very early this morning a truck unloaded all of the materials needed for the retaining wall. 

This delivery included:

  • 4 pallets of Sleepers (approx 60 sleepers)
  • A crate of post covers and post caps
  • approximately 25 posts, and
  • Cement mix to fix the posts

Soon after delivery, the contractors arrived and they they really got moving with and drilling the remaining post holes and fitting the first few posts.

The next few days will be focused on constructing the retaining wall and installing some of the drainage required. Should be an interesting week!

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