Basement as a living space – what details are important?

Our CEO was asked if it is feasible to convert the basement into a living area and what are the main problems that arise? Ert Soasepp, our CEO sheds some light on the matter.

1.What are main problems that might arise when people decide to reconstruct the basement as a living area?

Reconstructing the old basement into living areas is a popular solution to increase living space, especially in fully developed areas where extension works are not possible. In my experience in the construction sector, I have seen basements in all kinds of conditions and dealt with various obstacles in reconstructing these basements as dwellings. The problems are generally the same, as the basement is not originally designed to function as a dwelling. Usually, the basement is damp, water leakages are quite common and old basements often have degraded structures, water vapour condensation, unpleasant odours or growth of fungi. If the causes of the aforementioned issues are not eliminated during construction, similar issues might appear after finishing of basement reconstruction works. Construction faults could lead to interior damages and render these dwellings inhabitable. Disregarding such issues could result in toxic air and lead to health issues.

2.What should you focus on when planning this type of construction works? Is it ventilation, water barriers or something else?

First and foremost you should start with a building inspection to find out possible flaws in structures when planning to build dwellings in the basement. The aim is to find solutions to reduce the pressure of, and create barriers to keep off surface water, capillary moisture absorption into structures, air humidity, water condensation, and possibly reconstruction of the structures.

High surface water due to precipitation and melting of snow.

Also important is the ground of the lot and building height as compared to the neighboring lots. We have had an instance when the lot under construction had clay soil. Clay absorbs water quite slowly and the water from melting snow flowed to the loam soil of the lowest lot and water was basically leveled with the ground.

One possible solution is to use draining materials near basement walls, for example, sand or gravel. Rain water has to be directed into the rainwater system and drainage has to be installed as instructed by the manufacturer.  When backfilling the ground, the surface of the ground has to be designed to slope away from the building.

Water vapor and capillary absorption.

Previously, the main purpose of constructing a basement was to use it as a storage to preserve goods, and because of that, the room could be quite damp and cool. There is no layer of barrier on outside structures nor to the floor to keep off moisture and no isolation on structures. As a result water vapor condenses into the water near cold outside structures.

Start with outdoor constructions first.

First, you need to clean the walls with a pressure washer and remove all torn layers. Any surface roughness which exceeds the requirements of isolation material manufacturer has to be plastered or covered with concrete to form an even surface. When you are trying to pick out hydro isolation for the outdoor walls, you should make sure that the installed material does not act as a vapor barrier and any moisture could dry to the outside of the room. I recommend you avoid hydro isolation which leaves a thin layer of protection on the surface, as over the years water pressure and vibrations could eradicate the protection. Hydro isolation layers should penetrate the wall and close all capillaries in walls and under the foundation by using injection technology. Then, outdoor structures need to be insulated and the insulation materials must be protected from external effects as required by the manufacturer.

If you wish to avoid outdoor construction, it is possible to use hydro isolation and insulation inside of the basement, but I wouldn’t recommend it. Outdoor constructions are left without insulation and walls stay cool, which means that water condensation could appear on walls, resulting in mold and dampness in rooms. If you decide to use this type of construction, you need very precise calculations to find out the exact dew point and find a way to dry out the moisture in case of water vapor barrier leakages. Even if the technical solutions are correct, the outdoor walls stay wet as a result of external effects and the risks stay very high. Initial cost savings could easily be replaced by expenses to restore the foundation and carry out necessary outdoor construction works.

Indoor works of the basement

Existing floors have to be demolished and any unwanted surface has to be removed. Water draining surface, insulation, and hydro isolation need to be installed. In the case of the latter, the joining of foundation and floor has to be 100% moisture-proof. Before constructing the floor, you need to check the height of the sewerage connection point, which could be lower than the drainage of the basement floor. In that case, you have to have an overpumping system. Floors have to be covered with concrete, walls need vapor barrier solutions and air circulation or ventilation system. When people are present and use dwellings, they produce moisture. On average, one person produces approximately 1,5-2kg of moisture per day, in extreme cases up to 4kg per day. Ventilation has to be technically sound and air-conditioning norms have to be met. Otherwise, we would have excess humidity which leads to damages. The main idea is to have clean and fresh air and any moisture is directed away from the dwellings.

Before you cover the walls you should make sure that there are no signs of fungi on the surfaces. In addition to that,  you need to check that the building is not located in the area where Radon levels exceed the norms, otherwise, it needs to be directed off from under the building. In conclusion, moisture has to be dried out of the structures and then you can start with interior works.

3. If there is a definite plan to reconstruct the basement – is it something a DIY-person could do or you should prefer an expert?

Basement reconstruction work is not simply following the instructions on material installation or online advice. The solutions have to be based on the building condition and surface characteristics. Prior to construction, building expertise has to be carried out and a full project for construction and special design works must be in place. Without a construction plan, I would not recommend starting basement reconstruction to a DIY person nor an expert.

4. If someone wants to buy an apartment which has already been built in the basement, what should they check so they can be sure their new home does not pose any risk to their health?

In case of new developments or previously installed basement dwellings, I would start with documentation, photographs of the construction, and the project. If the documentation is incomplete or the construction works have been carried out according to the pre-project, I’d say not to buy.

An expert should look at the current situation and they should pay attention to all aspects mentioned above. Thermographic analysis could help define the quality of work.

You should discuss warranty policy and ethics with the developer or owner. If there are any faults, would they carry out only cosmetic works or look for and solve the underlying issue. Cosmetic maintenance is temporary and the construction faults will come up again even after the warranty is over.

5.Tallinn Kalamaja area has many apartments where some dwellings are on the ground floor and other parts in the basement. There are two types of solutions: some have built a kitchen and a living room in the basement and bedrooms on the ground floor. Others have a kitchen and living room on the ground floor and bedrooms downstairs. Which solution is more feasible?

If technically everything is correct – including planning and construction, then both solutions are feasible. The main question is the buyer’s budget and gut feeling. The allocation of rooms between the basement and ground floor could affect the budget quite significantly. It is not a hard rule, but in some cases, building wet rooms in the basement could be overly expensive. Personally, I would prefer to have private rooms, such as bedrooms and wet rooms in the basement and kitchen and living room on the ground floor.