How to knockdown rebuild an old house? Guide!

Knockdown rebuild an old house requires a significant outlay of money, so it is essential to know how to approach the entire process from start to finish step by step, what to renovate in each environment, how to do it and what to take into account when rebuilding an old house.

You have to have several things already known before starting to spend money, such as whether you want to build upstairs or knowing if you can build a second floor in the house , among other things.

How or where to start the knockdown rebuild of an old house?

If you are about to buy a house with the certainty that it needs to be knockdown rebuild, or if you are simply going to rebuild your house, the first thing is to make a diagnosis of the general condition of the house before anything else .

You have to inspect everything as much as possible, ceilings, walls, humidity. Although there are things that cannot be known until it is broken or opened, such as the state of the foundations or the facilities, for example.

But if we have a good eye for the appearance and aesthetics of the house we can have a suspicion of what period the house is from and be able to interpret what type of foundations it may have or what type of pipes for example (iron, copper, lead, etc.) but the real state we see when we discover and break.

Likewise, in an old house, it must be taken into account that the installations must be 100% renovated with hot and cold water, drains, gas and electricity.

The diagnosis of what needs to be changed and rebuilt is the basis for knowing where we stand, to know what we have to do and how to start, but above all things to control the knockdown rebuild and not get frustrated in the process.

The project and design of knockdown rebuild of an old house.

The second thing is to think about developing a knockdown rebuild project and a design , with this we will have even more certainty and control that we are going to do exactly. Are we going to leave the walls and environments as they are? Are we going to unite environments? Are we going to separate environments without walls ? Are we going to expand square meters beyond the original house?

All this is contemplated in a project and it is very important to do it to optimize expenses. The architect is the right person to go through the entire process and reach a satisfactory result.

A professional is trained to carry out all the steps, from making the diagnosis to knowing how to act, preparing the project and design based on the client’s requirements, to starting the knockdown rebuild.

Ideas and advice, what to maintain and what not in a reform?

There are many points and aspects to take into account, and in each one of them, proceed according to the aforementioned diagnosis. Below we will analyze each of these points taking into account some ideas and advice :

The walls and walls.

Unless they are in ruins and you have to demolish them on the walls, you have to look more than anything at the state of the plaster . That they are not detached or split, it usually happens that in the past a lot of lime was used in the plaster and this made them quite weak and this is noticeable when we want to make a hole, it is very easy for us because the plaster is very soft.

In these cases, if they are well attached to the wall, when they are hit with the fist they feel solid and not hollow, they can be left without any problem and a new thinner can be made on top .

What to do if there is no moisture in the walls? 3 possibilities.

  1. It depends on what level of humidity and where on the walls it is necessary to do one thing or another .

It can happen that the walls drip water from so much humidity, but this can be solved

For example, if the humidity is more than 1 meter above the floor level, it is most likely that the exterior plaster with the water-repellent insulation cracked and let in the rainwater that runs down the wall.

In these cases, the exterior plaster must be repaired with the water-repellent insulation and let the wall dry completely inside .

It may be that the joints of different materials, such as a window wall, have also worked a lot over the years and let moisture filter into the wall.

  1. If the humidity is seen near the ceiling, it may be for the same reason as above or because there is a water inlet through the ceiling or some hidden gutter .

It is very common to see halos of mold or fluff caused by excess moisture.

In this case, first of all, you have to repair the roof and completely cut off the entrance of water and then treat the wall

  1. If moisture is near or at ground level, the insulation layer is failing and needs to be repaired. And it depends on how the wall is built (hollow or common brick masonry) you have to make the corresponding arrangement.

If it is made of common brick, some intercalated holes are made every 15 cm and a liquid product is injected that acts as a water-repellent insulator, if it is hollow brick, the entire lap is channeled at the height of the plinths and it is filled with concrete and water-repellent.


Like the walls , you have to check that the structural part is fine , otherwise you have to remove it and make a new one. Once it has been decided that the structure is well , it is necessary to make sure that there are no leaks or water inlets anywhere .

In case of replacing the ceiling, it is necessary to know well the types of ceilings to install the most suitable one in each case.

If it is a flat tile roof.

The problem with the slabs is that if they are not kept properly insulated over time , they begin to have problems when they crack, water enters and the problems begin.

If you are considering replacing and making a new slab, it is useful to know the different types of slabs that exist so you know exactly which one to build.

If the building has a slab, the first thing is to isolate it from above . See if it has a carpet or subfloor with a slope and if it is necessary to remove everything until the slab is bare and make it new, and finally paint it or cover it with a membrane.

By making sure that we cut off the water inlet we can now repair the slab on the inside, the most common thing may be that it has burst in parts and the armor is exposed . See what state the irons are in, if they were wet for many years they are surely very rusty, you have to remove all the rust and paint.

If you have a slope with a wooden structure.

Another thing is to see if there are no rotten tie rods, and if so, it is surely because there has been a water ingress for a long time that wet the tie rod and rotted it, the tie rod must be replaced in this case .

In the event that there is a roof with a wooden structure, make sure that the borer bug has not attacked it . In these cases, it can be fumigated, but if the wood is heavily attacked, it will have to be replaced.

In old houses it is common to find the wood attacked by the borer bug.

You also have to see the state of the thermal insulation of the roof and realize what conditions it is in, in case you have to place or replace it, you have to see what types of thermal insulation for houses there are and think about installing one.


Disarm and remove artifacts such as the toilet, bidet, sink and bathtub, if any. Strip all siding and tear down to remove and replace old hot and cold water pipes .

As in a new construction, in a reform the bathroom is the most expensive, that is why distributing a bathroom correctly is important. If the bathroom is in very poor condition , it will most likely have to be dismantled in its entirety .

With regard to the floor, it would be necessary to see what state the sewage pipes are in, and if they are old concrete ones, for example, the entire bathroom floor would have to be lifted to replace them with new PVC ones.

In an old house, the bathroom is one of the environments where there is more dismantling and spending money , practically it is to make a new bathroom.

The kitchen.

Something similar happens with the kitchen as in the bathroom, you have to disassemble the furniture, remove the coatings and break to change the water pipes and in this case also perhaps the gas pipes.

If necessary, according to the previous project carried out, the pipe must be redistributed according to the new kitchen design.

You always have to work based on a previous project and design, based on the plans to know how to distribute the kitchen and. If the house is very old, the most common is to redistribute since the way a kitchen was used before is different from the way it is used now.

Now it is very common to locate a bar or island for daily use, the furniture is already designed differently and there are appliances that did not exist before for the kitchen, such as a dishwasher for example, which requires an efficient location and its necessary plumbing. There are minimum measures for the size of a kitchen to be correct.

If we do not do all this thought of in a previous project, the knockdown rebuild process can become chaos and a bad experience.

The installations.

In an old and deteriorated house, we must bear in mind that we are going to have to replace all the installations and that entails an important part of the total reconstruction budget.

Hot and cold water.

Old water pipes used to be made of lead, copper or iron. This must be replaced by thermofusion pipes . Not only the pipes that are inside the walls, generally the uprights that go down and up from the reserve tank also have to be replaced by thermofusion.

It is useless to change only one section and leave the rest because we believe it is fine, where we activate the water again it is very likely that the old pipes will begin to suffer and they will have to be replaced with the reform already finished.

That is why it is better to think about replacing everything .

Sewers and drains.

Formerly the sewage pipes were made of concrete or iron, the ideal is to replace them when we work in the bathroom and kitchen , and also replace the section (if any) that crosses the house to the outside.

So inside the home everything that is new sewer remains, outside then we will decide whether to change it or not .


The same old epoxy pipes are ideally replaced . Although it may be that these are still in good condition and can be used, but for this you have to see a registered gas fitter (part of the project) who can guide us and recommend the best and cheapest option.


In the past, iron tubes or pipes were used to pass all the cables of the electrical installation, also the connectors, mouths or boxes were made of iron, so it is very common to find many rotten and rusty sections as well .

Currently, plastic elements are used that last a lifetime and are better when it comes to safety .

In addition, the cables were also used from a different section, so many installations would not support, for example, the operation of an air conditioning unit, so the wiring must be replaced with new cables, as well as adding a circuit breaker and safety thermals.

What to do with the facade in the reform?

Not only what to do with the front of the house, but also the rear facing the patio. This is exclusively, more than anything else, design and depending on the style of the house and the owner’s aspirations, a design and an action plan are drawn up.

How much does it cost to renovate an old house per square meter?

As a first point you have to calculate the m2 of the reform to have a base. Below we express the average values ​​in US Dollars to not take into account local inflation, these values ​​are designed in a comprehensive reform where everything is made new:

Type of environment.Price per m2
Bedrooms, study, dining rooms and living rooms.280 / 350 dollars.
Toilets.600 / 700 dollars.
Kitchens.400 / 550 dollars.

List of expenses in a reform.

The correct thing is to have the calculation and computation of construction materials before starting. This is a list of minimum expenses when you want to reform or recondition an old house:

  • Architect fees.
  • File expenses : Only in the case that it is necessary to present work plans.
  • Labor unions : Bricklayer, plumber, gas fitter, roofer, installer, painter, electrician, carpenter.
  • Guild materials: Various construction materials, pipes, paintings, entrance doors and windows , bedroom, bathroom and kitchen furniture, electrical appliances, marble, bathroom sets, taps, interior doors , etc.
  • Miscellaneous : Cleaning, front and patio gardening, blacksmithing.

Conclusion: Suggested steps to knockdown rebuild an old house.

Summarizing the steps we saw above on how to proceed to knockdown rebuild an old home:

Contact and hire an Architect.

To make a diagnosis of the general condition of the house and based on that and the owner’s claims, develop a design project and an action plan.

Find and compare quotes

Of labor and materials. The more information we have on hand to budget the less additional we will have during the knockdown rebuild process.

Contact labor.

With budgets in hand, decide and hire first the construction company and then the plumber, electrician, gas fitter, roofer, painters, etc.

Begin the knockdown rebuild.

We already have the project and the hired company only has to coordinate the start of the work.

Once the work is completed, the end of the work must be requested , in this way it is certified before the regulatory entities that said work is closed.

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