Retaining Wall Drainage

I’ve previously posted about the importance of Drainage Behind a Retaining Wall to minimise the forces acting on the wall…. here is some advice on how to make sure it works.

You should aim to properly drain surface water away from the wall.

Then you need to consider drainage of water in the soil.

There are two sorts of retaining walls as far as drainage is concerned:

Permeable Walls (water can drain through the wall)

Examples of permeable walls are:

With permeable walls the water should seep out anywhere on the face.You still need to put a drainage layer behind the walls. This will ensure that there is a clear path to the seepage points and that any dirt is filtered out rather than staining the face of the wall. It can be worth using a drainage pipe behind the wall as extra security against water pressure building up.

Impermeable Walls (water cannot flow through the wall)


Examples of impermeable walls are:

  • Reinforced concrete walls.
  • Block Work or Brickwork Walls (see this link: Besser Brick Walls)
  • Sleeper walls…. With a plastic backing.

With these walls you need to make special provision for drainage.

Either:

  • Weep holes which are specially constructed holes through the structure at 1m, or less, spacing.

or

  • An  Agricultural Pipe(a perforated or slotted pipe see this Link Aggi Pipe) discharging to a surface water drain. A good idea is where possible have discharge points with silt pits (see this link: Silt Pit) at both ends of the wall.

Drainage Layer

  • For the drainage layer I would recommend  at least 100mm thickness of 10mm size, or smaller gravel.
  • If you are going to have a pipe the width of the drainage layer should be 50-100mm greater than the pipe diameter.
  • Isee lots of people use a geotextile round the pipe. In my experience thegeotextile can get clogged with silt and stop the drainage occuring.

For responsibility for Boundary Retaining Walls see Fairness

See Why Aggi Pipes Have Slots In The Base to learn more

 

Epoxy Coating: The Ideal Treatment for Your Garage’s Concrete Floors

Guest Post by Elisaveta Doncheva

More often than not, focusing on finding ways to increase a home’s resale value leads to obvious alterations and upgrades, such as furnishings that freshen up the interior and landscaping that gives the outdoors a nice finishing touch.

And yet, something as simple as treating the concrete floor of the garage with a little TLC could be the change that brings about the biggest impact.

In addition to the functional purpose this home’s feature has, which is handling the pressures from heavy-duty use from your vehicles or machinery, it also has an undeniable aesthetic role which may be somewhat understated.

To avoid deterring future buyers, or even an eyesore for yourself that could also be dangerous and risky for you, your vehicles, your machinery, tools, and what is not present in the space, it’s time to make some improvements.

Don’t worry, it’s as simple as adding durable epoxy coating for concrete to get the desired makeover.

You’ve got a range of versatility available, differing not only in price but carrier agents too, giving you the chance to choose from solvent, solid, and water based.

Is It a Good Idea to Put Epoxy On the Garage Floor?

It’s a type of coating that’s meant to last for years and years, and it truly can with proper floor maintenance.

If it’s good for commercial purposes in industrial applications that require the best of the best in terms of floor protection, why should it be any different from residential applications?

When applied, there’s a specific permanant chemical reaction happening which gives this material some exceptional qualities for the surface it’s added to.

To give you an idea, the following are just some of the benefits you can expect to reap once you treat your floors with the suitable resin and hardener mix.

The Smooth and Shiny Appearance

The floor can make or break the space’s appearance, and all it takes to get it from drab to fab is a nice layer of epoxy coating for concrete to get smooth and seamless elegance.

Even though elevated aesthetic may not be your goal, least of all for a utilitarian area like the garage which serves as a parking area, workshop, and storage for your seasonal equipment or home-brewing equipment, the sleek and elegant touch would surely increase the overall curb appeal.

And, you can have fun choosing the coating – for a polished ambience, why not pick one of the eye-catching metallic mixes?

A mixture with details from mica or quartz equally makes for a unique aesthetic that additionally doubles for better traction of the floor too, so you amp the look without sacrificing the function or convenience.

The Increase in Protection

Instead of serving as the base, the garage floor epoxy is a layer added over the already sturdy concrete floor, taking up the role of protector for the underlying surface, shielding it from impact as well as wear and tear that might result in cracking and crumbling.

Since there’s more than one layer added, usually you get a thick coating that covers your precious concrete flooring, giving it an increase in durability.

This explains why upon application the possible defects of the floor might have magically disappeared with each and every layer of the coating, offering a sleek and smooth finish.

It’s exactly this that gives you peace of mind since usually defects can be the opening points for moisture to make its way through and damage the concrete little by little.

The Increase in Strength

Impacts, shocks, extra weight – you name it, the coating can handle it all.

Unlike other coatings, epoxy stands out from the rest with its incredible tensile strength, and the secret lies in the addition of the hardener, specifically the polyamine material.

Depending on the type of epoxy and hardener you choose, you can significantly increase the concrete’s ability to stand up to all the pressure you’d put it through.

If the bonding with the underlay surface is good, you can expect there to be strength in the resistance to peeling and tearing too so you won’t have to worry about those heavy loads.

The Increase in Safety

The garage that doesn’t have windows or proper illumination can easily become a place that compromises the safety of anyone going inside, but this too could become a thing of the past with the simple addition of a few layers of an epoxy concrete floor coating of your choice.

This is due to the material’s ability to reflect the light, which results in the brightening up of the whole area.

Moreover, with certain mixes of epoxy and hardener, it’s possible to increase the safety to reduce the danger from slipping accidents.

If a slick surface isn’t your thing, and you wish to further boost the safety, you could add your own ingredients to the mix, including polymer grit, gravel or sand.

The Resistant Properties

It is more than resistance to water and moisture.

It is also resistance as well as heat, chemicals, and even impact, it’s an investment that more than pays off in the long run.

The thicker the layer of coverage, the more of these incredible properties you can expect.

The Long-Lasting Result

As mentioned, this is a covering option that keeps on giving time and time again if we keep its resistance properties, strength, and durability in mind.

As such, it’s a much more reliable and convenient option than other covers in the likes of concrete paint, or tiles, especially if we consider the lack of need to redo the epoxy layering for many years.

The Eco-Friendliness

Sure, it’s a chemical, but that doesn’t mean it can’t be eco-friendly in its own way.

As it’s not that difficult to install, needing only a few essentials, and it doesn’t need to be recoated that often, it’s more helpful for the environment than other alternatives.

If you think about it, it’s quite cost-effective too so your budget won’t be significantly impacted once you take care of the proper installation.

How Do You Take Care of Epoxy Floors?

We’ve already discussed the outstanding properties of epoxy, including its durability, but it wouldn’t hurt to get in the habit of maintaining it to ensure it lasts as long as you expect it to, or even more.

Sweeping to get rid of dirt, dust, and debris is the basic step you should implement, followed by mopping.

Getting rid of stains should be done immediately after they occur, with an emphasis on using epoxy-suitable products, from cleaners to the right tools for the job, to avoid scratching the coating yourself.

Also, remember that prevention is better than cure, and in the case of the coating, it’s advisable to protect it from heavy objects by using the appropriate mats and furniture pads. A little care goes a long way!

Contracts – Site Possession

Under the terms of a “Standard’ Building Contract you will be required to grant the builder ‘Exclusive Possession’ of the site once the builder is ready to start.

This means that the builder is responsible for, and is able to control, all people coming onto the site during the construction period.

The reasons for this are:

  1. Safety – The builder is responsible for the safety of everyone on site.
  2. Scheduling – Its harder to effectively schedule trades when you could be delayed waiting for other people to complete work.
  3. Cost – If the builder’s workers are delayed by having other workers in the way it can mean extra costs.

Practically what ‘Exclusive Possession means for you is:

  • Before you go onto the site you should contact the builder, who may only allow you on site if accompanied by the Site Supervisor.
  • If your bank, or building inspector, want to go on site to check on the works they also need to make an appointment with the Site Supervisor.
  • You may not be able to have other work done at the same time by other people. For instance:
    • Landscaping.
    • Home Automation.
    • Swimming pool or Spa installation.
    • Additional Electrical work.

If your builder says your other tradies or contractors can go on on site make sure you get their permission in writing with any conditions clearly stated!

Rural and Large Blocks

If you are building on a rural block, or just a large urban block it can be worth marking out, and even fencing, the house building site.

You then give the builder possession of the house building site only, and work on the remainder of the block.

 

Did your builder allow you to bring your tradies on site?

 

For similar posts see Contract Conditions

 

Insulation Basics – Brick Veneer Walls

This post will help you understand how much heat you lose through walls. A previous post has explained ‘R’ and ‘U’ values

When considering insulation a typical Australian brick veneer wall would be:

Element

R value

Outside surface air layer

0.03

110mm brick

0.08

25mm cavity

0.12

R1.5 Insulation

1.5

Plasterboard 10mm

0.06

Inside surface air layer

0.12

Total R value

1.91

U value = 1/R

0.51

The heat losses or gains for 150 sq m (fairly typical external wall area) of this type of brick veneer wall at 15 degrees above, or below, outside temperature will be:

Area x ‘U’ x temperature difference = watts per hour

150 m2 x 0.51 x 15 degrees = 1178 watts per hour

Heating/Cooling Requirement = 1.17kw/hour

To change the U value calculation simply change the value of the element or add an element in.

Example 1 Changing the Insulation to R 2.0

New Total R = 2.41

New U = 0.41

Reduced Heating/Cooling requirement to 0.92kw/hr

Example 2 Adding a reflective building wrap to example 1 (increases cavity R by 0.18

New Total R = 2.59

New U = 0.39

Reduced Heating/Cooling Requirement to 0.87kw/hr

Remember this isn’t the total heating requirement as heat is also lost through windows, ceilings floors and ventilation.

 

See Insulation for similar Posts

For Posts about Green Building see Sustainability

Retaining Wall Fairness

In Western Australia subdivisions are usually completed with retaining walls in place on the boundary so that all blocks are level.

For the rest of us if we are faced with a sloping site a retaining wall may be needed before you can build…………..but who pays?

Here are a few examples

Block A is sloping down towards the boundary and Block B is fairly flat

Block A has to build up their block and should be the only one to pay. The wall should be within their block.

Block A is fairly flat and Block B Falls away from the Boundary

Block B has to excavate their land and should be the only way to pay. The wall should be within their block.

The slope affect both Blocks A and B

As one block has to be build up and the other has to be excavated both should share the cost. This however can a fairly complex with some of the issues being:

  • Should the overall cost be apportioned if one site has to be built up by 1m while the excavation needed is only 0.5m.
  • The location of the wall particularly on slopes.
  • Fences on the wall
  • What happens if you are keen to build but the other block is unsold or the owner is in no rush to build.

Each block having their own wall may be a solution, however these can’t be too close together (See this link for more: Retaining Wall) which may be an issue if you need to site the house near the boundary.

In cases like this you really need to make sure your lawyer sews up a watertight agreement on retaining walls before you buy the block.

This link: Understanding Retaining Walls gives an understanding of the technical issues

 

Understanding Retaining Walls

Its quite usual when you have a sloping site to need a retaining wall to make the land you build on level.

You might need a retaining wall just to have a flat garden.

Retaining walls are not simple structures.

They have to withstand significant loads and need to be properly designed and constructed to avoid failure.

Loads On A Retaining Wall

The sketch above shows a retaining wall. There are three main loads on this wall:

  1. A wedge of soil (shown as a grey triangle) tending to slide down. The size of the soil wedge depends on angle ‘A’ which will vary depending on the soil. Typically the loading will be over 1 tonne/m length for a 1m wall. The taller the wall the greater the load.
  2. The additional weight of a car (or any other above ground load, such as piled up dirt) which will be adding to the soil load. Say another tone per m
  3. If water is allowed to build up behind the wall the load is increased by the water pressure. Almost another tonne of force.

Methods of Failure

There are 3 ways simple retaining walls typically fail:

  • Toppling Over
  • Sliding forward on the foundations
  • Breaking with the top separating from the bottom

As one of the main factors in holding up the wall is the strength of the soil at the foot of the wall:

    • DO NOT excavate in this area or steeply slope the soil away from the wall without checking with a designer.
    • DO provide proper Drainage Behind The Wall.
    • DO slope the surface below the wall gently away from the wall. You want to prevent the soil supporting the wall becoming soft and failing.

Regulations

Usually all retaining walls over a certain height (‘H’ in the sketch above) require a permit from the council, who will want to see that the wall has been properly designed.(Depending on the Council this height can be as low as 600mm)
‘H’is the difference in height between the upper and lower LEVEL areas.

NB The following walls all have an effective height of MORE THAN 0.9m.

In the case of the tiered wall above you would need to set the walls at least 2 x H apart (Even more in bad ground) before the walls could be considered as separate.

The reason why you don’t need a permit for smaller walls is to save the councils extra work, as they think that damage from a smaller wall failing will be fairly small.

It doesn’t mean you don’t need to make sure its properly designed if you want the wall to last.

What Can You Do

This is NOT  a lesson on how to design retaining walls just helping you to understand the loads involved so:

If you are uncertain its best to get it all checked by an engineer!

 

For advice on who pays see Retaining Wall Fairness

 

Render or Brick?

Rendering popularity comes and goes……………… However I think “Why pay more for a something that is only going to require painting in the future?”

As my old woodworking teacher once told me “There’s nothing wrong with being lazy as long as you are intelligently lazy.

That means getting the job done but saving effort, both now and in the future.”

Positive

Rendering does have its place:

  • It gives a good finish if you are building using Hebel blocks or Foam Panels (See this link: Rendered Foam Walls), which you may prefer to use as they have a better thermal performance than bricks.
  • The render, particularly if painted a light colour, will improve the thermal performance of the walls.
  • You need to do it for some of the Home Builder techniques such as straw bale housing, or even if your DIY bricklaying is a bit rough.
  • Its handy if you are renovating a house and the previous builder has painted the bricks.

Negative

Apart from the exceptions above here’s why I don’t like render as a final finish:

  • Additional cost at time of construction.
  • Is it really hiding the use of leftover bricks from previous jobs and perhaps poor workmanship by the builder.
  • It can look fairly flat and bland in large areas like the house below:

  • Future time cost and effort in repainting.
  • If you get building movement it really shows up, with a crack across a flat plain wall. It’s then very hard to satisfactorily repair and hide the crack.
  • Render really shows dirt, spiders webs,and water stains.

Bricks are making a comeback as people who have rendered 10 years ago now find that the additional cost was only the start.

Having a house painted every 10-15 years is an expense that basically starts at $12K. Personally I’d prefer a family holiday .

Render costs around $20,000 on a 30Sq home, plus painting, plus more for maintenance……Brick veneer requires a wash, at the most, with a low pressure hose.

Some people say the modern Acrylic renders are better than the cement renders but I remain to be convinced.

What do you think?.

 

Whichever you choose the most appropriate Brick Dimensions will make the walls easier to build.

More about selecting finishes including 24 pages of Check Lists in the ‘Selection / Pre-Start Guide’

 

Agricultural Drains

Agricultural drains (often called aggi drains) are used to:

  • Drain waterlogged ground.
  • Avoid soil heave by keeping your foundations dry (see this Link: Protect foundations)
  • Keep the soil behind retaining walls dry. (see this link: Retaining Walls)

Existing Drains

In the old days agricultural drains used to be constructed out of short lengths of clay pipe butted together without proper joints. (If you are building on a demolition site you may still come across these pipes.)

The water seeped into the pipe through these butt joints.

Current Method

Nowadays agricultural drains come in two types:

    • White slotted UPVC pipes with longitudinal slots which come in straight lengths (usually 6m long).
    • Black corrugated UPVC pipes with lateral slots that come on coils of various lengths.

For domestic jobs the black corrugated coils are probably the easiest option.

DON’T get the pipes with a Geotextile ‘Sock’ around the Pipe (see this link:  Geotextiles Around Drainage Pipes)

Laying Aggie Pipes

You don’t need to be a plumber to lay agricultural drains in your garden. Some advice for laying the pipes are:

  1. The pipes should be laid at a gradient of no flatter than 1 in 100 (1cm in 1m) to the point to which the flow will be directed. A gradient of 1 in 50 is better!
  2. When excavating a trench for agricultural drains you need to dig the trench at a width of at least twice the width of the pipe and at least 25mm deeper than the level of the pipe.
  3. Lay 25mm of 10mm gravel in the trench keeping it at the set gradient.
  4. Lay the pipe along the top of the gravel keeping it as straight as possible.
  5. Fill the trench with 10mm gravel to 100mm below ground level.
  6. Fill the last 100mm with topsoil.
  7. Make sure you have a silt trap before the point where you connect to the point of discharge.(see this link:  Silt Trap)

Geotextile around Drainage Pipes

Many articles about installing agricultural drains recommend that you place a geotextile in the trench before the initial gravel surround and then wrap the geotextile over the gravel afterwards.

You can also buy agi pipe with a geotextile “sock’ around it like this:

The idea is that the geotextile prevents the gravel,or the pipe getting clogged with fine materials.

Its something I used to do, but . . . I DO NOT  recommend this anymore.

The Reason

Practical experience has shown that what happens is:

  • If you wrap the gravel with geotextile the geotextile actually collects all the  particles on its surface and gets clogged up. This stops the water getting to the gravel and on through to the pipe.

or

  • If you wrap the pipe and put the sock around the pipe its only the very fine particles that get through the gravel but they then get caught in the ‘sock” in front of the slots. This again stops water getting into the pipe and draining away.

Recomendation

It far better to just go for a 10mm or smaller gravel surround.

This stops the larger particles.

Any fine material that gets through the gravel will be that fine it will easily pass through the slot and likely to get washed down the pipe.

 

See Agricultural drains for more information.

Wall Dimensions Standard Bricks

When you are deciding about building dimensions its better to take into account the size of building materials.

With brick veneer being so popular that means the dimensions of the bricks.

Make sure that all lengths, are based on either all complete bricks, or complete bricks with one half brick.

Similarly all heights should be based on complete bricks. Doing this has the following advantages:

  • Less wastage of bricks
  • Savings on labour due to less cutting of bricks
  • Stronger walls due to more regular bonding

The Work (design) Size of a standard brick is: 76 mm high x 230 mm long x 110 mm wide. These seem unusual dimensions but they are based on the old imperial dimensions of 3 inches by 9 inches by 4 inches.

When calculating overall wall dimensions it is normal to allow for 10mm vertical and horizontal mortar joint between bricks.

I have included  ‘Tables of Dimensions for Brickwork’ at the following two links:

Checking Bricks Meet Specification

Clay brick sizes may vary after they are fired but size variation between bricks averages out when blended properly during laying by a good bricklayer.

There are three dimensional quality levels for bricks DW1, DW2 and DW0

If you want to check the quality of the bricks the normal method of measuring is to measure 20 bricks dry stacked together against the work size of 20 Bricks.

  • Dimensional Category DW1 means the height and width will differ by less than plus or minus 50 mm from 20 times the work size, and the length will differ less than plus or minus 90 mm.
  • Dimensional Category DW2 means the height and width will differ by less than plus or minus 40 mm from 20 times the work size, and the length will differ less than plus or minus 60 mm.
  • Dimensional Category, DW0 means there are no requirements. This is usually reserved for non-standard shaped bricks and bricks that have been rumbled or otherwise distorted during the manufacturing process for aesthetic reasons.

Planning some building work in the garden? see Brick Fences

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