Seal a basement window properly


The windows in the basement are often neglected, in some cellar rooms, the owners often do not come all year. But there is often a need to seal basement windows here. However, it is about sealing against conventional humidity and cold draft, but not standing in light shafts water or even flooding. Below you will learn step by step how to properly seal cellar windows - but also under what circumstances it takes more than a simple caulking.

Seal basement windows, save on heating costs and gain living comfort

Basement windows are often neglected when it comes to sealing, because you are not so often in the basement. This can cause unpleasant cold bridges, which are triggers for icy floors on the ground floor. With corresponding leaks in the basement windows, the heating costs rise dramatically. With simple means, you can seal your basement windows and thus reduce heating costs again. Even the unpleasant floor-radiating cold that can hardly be contained in otherwise well-heated ground floor rooms can significantly reduce this.

Basement windows seal with water in the light shaft

But there are always requests to seal cellar windows under different aspects. For example, when, after intensive or long rains, water rises into the light wells and threatens to penetrate through the basement windows into the basement. In almost all cases, the cause is in a wrong drainage system around the house (not water-permeable soil layer, old and broken drainage, etc.) to seek. Even if you were to seal the basement window, the water would still be around the house at the same height and could penetrate into the masonry.

Seal a basement window properly: properly

In case of heavy rain, water penetrates from above into the cellar shaft

A rare exception, where you should seal the light shaft itself, is when the water does not seep fast enough in heavy rains and threatens to penetrate cellar windows. Since next to the window, the masonry is threatened, in this case advised to already mentioned sealing the basement shaft. If you are looking for waterproofing options for basement windows at risk of flooding, the installation of special flood protection windows is recommended. The following step-by-step guide will help seal basement windows against cold drafts, as the other causes mentioned here require a different approach.

Step-by-step instructions for basement window sealing

  • Suitable sealing material
  • grease- and silicone-dissolving cleaner
  • Carpet knife or scissors
  • Candle or tealight
  • spatula
  • possibly an easel or ladder
  • possibly work lamp

1. Preparation

If you do not want to seal all basement windows, but you are looking for leaks, you should use a candle or a tea light. Guide the steady flame along the window frame where the closed window rests. If it comes to a draft, see it immediately at the flame.

Preferably perform this search on a day of extreme cold outside. Cold drops down and the pressure of the cold air builds up so strongly on the low-lying cellar window (for example in the light shaft), the draft becomes correspondingly strong.

Beware in boiler rooms! Hazardous and easily flammable vapors can form here. Therefore, when sealing these basement windows, it is best to consult the responsible chimney sweep, as to whether sealing is permitted at all.

2. The sealing from the basement window

Depending on the basement window you will need different sealants. If it is a heavily distorted window with large gaps, a tubular or u-shaped rubber sealing tape may be the best choice. Otherwise, tape manufacturers will also provide appropriate adhesive sealing tapes.

If necessary, carefully remove old seal residues with the spatula, then clean the side of the window to which the tape is to be glued with the cleaner. Then fit the gasket and glue firmly. To do this, keep the window closed as soon as possible after pasting.

Tips & Tricks

Do not keep your basement windows closed all year round. Moisture can also penetrate through the masonry. Moisture can also flow down the cellar access with the cold. This moisture must be able to escape. Otherwise, damp spots will form on ceilings with condensation that tends to mold. The mold spores can be distributed throughout the house.

It is essential to observe the ventilation regulations for heating in the basement. The responsible chimney sweep advises in detail.

In the case of cold sealing: if it is not possible to seal it because of a cold floor in the rooms above the cellar for a variety of reasons (for example heating regulations), consider insulating the cellar ceiling from below, from the basement room.


Video Board: Basement Waterproofing | Seal Leaks With Expanding Foam - TXU Energy & Energy Star