It may look nice, but did your builder avoid the most common mistakes when creating your home extension?

Error 1 – Excavations and foundations

The first part of the house extension is usually with the foundation and you will be surprised to learn that at least 25% of the foundation is not placed directly under the walls on top. Digging off center or in the wrong position is quite common and in one particular case I had a builder excavate for a two room side extension on the wrong side of the line that was installed. His ignorance doubled the cost of excavations and foundations in the blink of an eye.

Error 2 – DPC membrane and waterproofing course

This part of the expansion of your house is a minor but vitally important job. If done poorly, moisture can get into new walls in a matter of weeks and over a year or cause serious moisture problems.

On a site I inspected a few years ago, the builders had used plastic debris bags to form a layer of moisture protection instead of using the correct width dpc roll.

Mistake 3: Extensions are rarely square

The vast majority of home extensions do not have 1 square corner. At least 98% of the builders I have met in the last 30 years had no idea how to verify if the tract on the house they were building was in fact square with the property.

Error 4 – Services on the Floor

Time and time again I have come across copper pipes and electrical wires being laid directly into concrete floors without any kind of coating or protection. Copper pipes corrode quickly when directly encased with concrete, as the cement practically eats away at the copper. As for the idea of ​​electrical wires running around the concrete without any sleeves, that just gives me the creeps.

Error 5 – Windows and doors

You may think this is an easy job, but again, it is quite common that the height of windows and doors are often mismatched because the floor height was not placed correctly or the mason made a mistake. Ideally, all you should see at a garden entrance is the wooden threshold and not a small wall below it. In some cases you don’t even see the threshold because the frame was set too low and this too is simply poor workmanship.

Error 6 – Floor heights

New floor heights are amazing in the many ways they can be messed up. Probably the worst case scenario is when they are too high, usually resulting in a step up from the main house, all because the builder didn’t drop the ground a bit more when building the extension.

Error 7 – Ventilation to the subsoil

When building a side or rear extension to an older property with ventilated subfloors, it is critical that you continue to provide ventilation through the new extension floor. It’s a simple task that costs a fortune, but eight times out of ten the builder doesn’t bother and the end result is usually dry rot within a few years.

Error 8 – Isolation 8

Some years ago extensions were built with little or no insulation. I am happy to say that times have changed and you are now required to have insulation in your walls, ceilings and floors. Most councils now insist on additional dry lining with insulation backed board for breeze block walls, so make sure your builder will accommodate. Also make sure they put at least 100mm of insulation on the concrete floors. If you don’t tell them, they won’t bother and building control may not notice.

Error 9 – Drain

This has to be one of the easiest tasks that is invariably done poorly or indeed missed as much as possible.

When adding a full-width extension, you should always let rainwater through from the main roof. Time and time again you see this water being allowed to discharge into the extension roof, which is simply not supposed to happen as it will always lead to premature problems.

The other point, of course, is that rainwater should not be discharged into soil piles and should have its own means of entering the sewage system or absorbing it. If your builder messes up, it’s usually a big problem to fix it at a later date.

Mistake 10 – Invasion

I saved trespassing for last mainly because it’s an unknown word to builders and most homeowners, but it can be quite the nightmare if it happens on your construction project.

Invasion is where you build over the boundary line. Most people think this relates only to the physical terrain, but in reality, time and time again you see pipes, gutters, and caps clearly encroaching on other property, which can be a nightmare to correct.

In most cases, the builder carries out the encroachment out of sheer ignorance, but may leave you with a hefty bill to correct or, indeed, legal fees should your neighbors sue.

Resume

The best way to stay ahead of the game is to stay informed.