After the installation of windows and/or doors is done, Fenestrum provides the customer with a brochure where the process of use and maintenance is described thoroughly. We provide our products with a five year warranty. During this time we will remove all the defects that we are responsible for free of charge. In case our specialists identified that defects occurred due to the inappropriate maintenance or exploitation, we will remove them for an additional fee. The fee size is determined by the specialists after the visit. The hardware in windows and doors is provided with a two year warranty.


Fenestrum takes care of the clients even when the warranty period is finished. We will repair our products, change worn out components or cracked glazing, repaint the products and provide other necessary work. Our specialists will arrive to the customer’s home, assess the need for repair and arrange the necessary repair costs with the customer.


Below are the most important guidelines that every customer should follow to ensure the durability of windows.




When exploiting timber windows, it is necessary to understand that they are a high quality product which requires much more maintenance than plastic windows. Most often, the products are installed to an unfinished premises i.e. newly built houses, flats and offices where products are damaged during the finishing works – splashed with mortar, glazing and frame is scratched, various building waste come in contact with the moving parts of the hardware. Due to the inappropriate microclimate (temperature and humidity) in the premises, timber windows and doors warp or bloat. When timber windows and doors are installed in a newly-built premises, we especially do not recommend delaying the façade construction works and leaving wooden products for the cold season (autumn and winter) since the products will be directly affected by dampness and cold during this period


We recommend our customers to make sure that moisture absorbers are placed in the premises and they are ventilated enough during and a few months after the finishing work (plastering, concreting, and coating) because when humidity increases, mold can occur on the frame, windows can warp (leak, hardly open or close), varnished surface can become pale and timber can change its color. Coating and timber tint can change due to the building materials by which windows are splashed or had other type of contact with them. In this case, the products are damaged beyond repair.


During the finishing work, the products must be covered with transparent sheets, cardboard and so on, so that the plaster, coating, or paint do not come in contact with painted or varnished surfaces, glass, locks, hinges and other parts of hardware. It is recommended to keep taped sheets for no longer than 72 hours. After installation, it is necessary to scratch the sheet in a way that the dampness would not accumulate between the product and the sheet.


Having scratched the glazing or the frame, the product becomes aesthetically damaged. Such defects are rarely removed without changing the product or its separate parts.


When various dust that occurred during plastering, concreting or coating of walls falls in the cladding, it gets stuck, hardly work or sometimes even break. In addition, panels that close inappropriately can warp.


One of the most commonly neglected conditions when using timber windows and doors is the microclimate of the environment. In case of inappropriate microclimate, products bloat and warp. The can start rotting or molding, become leaking and hard to use. Clouded windows from the inside are one of the signs that the temperature and humidity relation (microclimate) is inappropriate. Timber windows and doors have to be exploited in the premises where the humidity level is not too high, since condensation on the windows and doors can influence the occurrence of mold, deformation of glazing beads and frame.


It is necessary to keep windows in such a way that an anti-corrosion coating or hardware would not be damaged or broken, respectively.


To prevent window or door hardware from breaking, do not load the window panel with an additional weight, do not support or lift it with additional items.


Do not put any additional items between the panel and the casing (wires or cables), the frame or the hardware can deform because of it.




Glazing does not require any special maintenance. Here are a few essential recommendations:

  • It needs protecting from the outside effects that encourages cracking;
  • Glazing needs protecting from slamming that can be caused by draught;
  • Do not leave open windows without supervision. It is advisable not to open them on windy days;
  • Do not stick any sheets on the glass (toned glass especially). Due to the different thermal stress the glazing can crack;
  • All toned glass area have to be illuminated or be in the shadow. If only a certain area of the glass is in the shadow, unevenly hot glass can crack.
  • If the glass is affected by a higher than 36o C temperature difference, the possibility of thermal cracking is very high;
  • The distance between the heating devices and the glass has to be no less than 20 cm;
  • The distance of stove and fridge from the glass has to be no less than 30 cm;
  • The temperature of heating devices next to the glass should not exceed 65º C;
  • Having started heating the premises, raise the temperature gradually not suddenly.
  • When using calorifiers do not turn a warm air towards the glass.
  • The risk of cracking increases due to the heating and conditioning devices near the glass;
  • Thermal cracking can occur due to the insufficient heat in the premises (especially if it is not heated during the winter);
  • The glass surface cannot come in contact with internal or external blinds as the glazing can crack due to the temperature difference. The distance between the blinds and the glass surface has to be no less than 2 cm.


In order to keep your timber windows beautiful and undamaged, you must maintain varnished or painted coating every year. It is advisable to clean windows using measures specially for coating maintenance. When using such measures, the surface is covered with a protective layer, which protects products from dirt, coating becomes more elastic and shiny. You can apply these measures with a cloth or sponge. The surface does not require an additional polishing. Read the instruction manual and follow it strictly before starting. Painted coating needs to be cleaned and lubricated once a year (e.g. before the winter, and varnished coating – twice a year (best in the autumn or spring).


If coating of your windows and doors changed its tint, it most probably is a consequence of environmental effects (sun, weather, humidity).


Clean dust and dirt off the surfaces at least twice a year. Mold and lichen can occur in case of not cleaning them. Brush clean surface with a slightly wet cloth or a sponge. Do not use strong household cleaners as they can damage the varnish or it and timber can change color. In addition, strong cleaners can damage the glass or the hardware.


It is advisable to thoroughly read the instructions of cleaners and follow them. When cleaning mason or other surfaces near the window, cover or protect it in any other way. If an acid cleaner came in contact with the surface of the window, wash that spot with clean water immediately.


Do not use powder or other abrasive cleaners (rough or with hard spheres) since then multiple micro scratches will occur on the window.
We recommend hiring professionals for the window repaint.




Constant (at least once a year) lubrication of claddings ensures easy functioning and helps to avoid early wear and tear. We recommend using only machine oil with no acids in it for lubrication. It is also advisable to check the stability of screws and screw or change them if necessary.

The windows will function year after year and safety of the users will be ensured if the directions below will be followed:

  • Do not turn the handle when the window is opened;
  • Window panel cannot be loaded with an additional weight;
  • Window panel cannot be pressed to the embrasures;
  • No items can be put between the window casing and panel.




When cleaning the windows do not forget about gaskets as well. Various waste can tear or deform them. You will easily check whether the drainage holes are not clogged up by opening the window panel. Holes are in an aluminum dip on the bottom of the window casing. If there is waste or dirt in the holes then clean them, so that the water could run outside, otherwise it can accumulate on the frame and leak into the premises.

Mentioned holes are in the panels. If these holes are clogged, water accumulates between the frame and the glazing. Over time, the glazing starts to get cloudy from soaking in the water, selective coating oxidizes and stains occur. In addition, accumulating water moistures the frame (it starts to rot) and the glazing beads deform.




Clean plastic and aluminum parts with a mild cleaner and water solution. Abrasive cleaners can scratch the surface of these parts, damage the paint. You can use mild alcohol and water solution cleaners. Do not clean the glass with powder abrasive cleaners. Never clean a hardly removable dirt (paint, leftovers of building material and so on) with sharp items (rough sponges, cloths, scissors, knifes, shaving blades and so on). Using sharp items you can scratch the surface.


Fenestrum draws the customers’ attention to the fact that warranty services are NOT provided, and defects of the products are removed at the expanse of the customer if:

  • The product is mechanically damaged during transportation, installation, exploitation process or due to the inappropriate building process when the customer or individuals hired by one perform these actions;
  • The product was used with an opening and closing mechanism which had been adjusted by the customer and the timber frame or an opening and closing mechanism was damaged because of it;
  • The customer have not paid for the products;
  • The product was changed or modified by others than a manufacturer or its representatives;
  • Materials damaging to the paint coating or anti-corrosive layer were used for cleaning;
  • The product was used in violation of the exploitation rules;
  • The products were already repaired by others than the representatives of the manufacturer;
  • Building waste, which occurred in the process of finishing or other works, was not cleaned from the claddings, the customer did not protect the product;
  • The customer painted gaskets, locking mechanisms, handles, plastic finishes, silicon threads next to the glazing and other connecting parts during repaint.