Condensation Below Floors


John,

I recently went into my under build and was quite alarmed to find that a large area of the underside of my floor above was dripping in water. What do you think is the cause of this problem and what action needs to be taken.


Charles P. (Parcent)


Hi, Charles,

There are two possible reasons that would cause water to drip from the underside of your floor, condensation or a broken water pipe.

Condensation – This is a common problem in floor voids of Spanish properties and if left unchecked can lead to a host of problems, mould and fungi to name but two. In some properties especially where the floor to the under build is just earth the amount of water found dripping can be phenomenal. The least expensive way to stop this accruing is to introduce cross ventilation into the under build void; air will need to pass from one side of the property to the other via air grates in the external walls. The flow of air is naturally achieved by the positive and negative pressures that exist around any property. This movement of air within the floor void will allow the moist air to be removed and the void will eventually become dry, in simple terms the more ventilation you provide the dryer you’re under build will become. The number of air grates required will depend on the individual property, but as a rule of thumb they should be provided at no more than 1.0m from corners and a maximum of 2.5m apart on all external walls. Also to achieve true cross ventilation through the property it may be necessary to remove some individual blocks in the supporting cross walls below the floors, but do not to break the structural ‘U’ beam. The ‘U’ beam is usually sighted directly under the concrete floor beams and continues around the property including the internal cross walls.

Broken water pipes – In some properties the central heating pipes and or the hot and cold water service pipes that carry the water to the bathrooms, kitchen etc. are located within the floor. It is common practice for pipes to be laid directly onto the top of a concrete floor, and then a 5 cm. (2 inch) layer of small chippings is laid above the floor which also surrounds the pipes and finally the floor tiles are bedded onto the top of the chippings. This is good as far as not being able to see the unsightly pipes but not so good if you need to service the pipes, extend the system or even worst repair a leaking pipe. If a pipe starts to leak it is not always evident where the leak is, water may have tracked along the concrete screed above the floor beams and be dripping below the floor in a different place. Once you think the position of the leak has been determined the floor tiles will need to be broken up, the leaking pipe repaired and the floor replaced all quite straight forward if you have plenty of spare matching floor tiles.
There are several ways to determine if a pipes below the tiles is leaking, most methods involve a plumber and some form of pressure testing the system; however the layman can carry out two simple tests.


 If you think you may have a leak in one of the central heating pipes, look at the boiler, modern boilers have a water pressure gauge, this should be reading 1.5 -2.0 bar, if this is low water may have been escaping from the pipe work, very low pressures will prevent the boiler working. If you think you have a problem it would be wise to call a competent plumber to reset the water pressure, if the gauge then continues to fall, you have a leak. Please note that constant bleeding of the radiators will also reduce the pressure in the system.


If you consider your problem lies with the hot or cold water service pipes turn off all taps, washing machine, dishwasher, garden watering systems etc. and inspect your water metre in the road for any movement, neither the wheel or the numbers should be moving. Make a note of the position of the wheel and take a reading of the numbers, go back in an hour or two to see if there has been any change. If the wheel or the numbers have moved then water is escaping somewhere. This is not a fool proof method, as a very small leak may take a long time to register on the metre, however with the amount of water loss that you are experiencing some movement will be seen. Again if you think you have a problem with any pipe work call a reputable plumber.

John Phillips (F.I.A.S. F.A.B.E. M.I.B.C.O. F.F.B. M.R.S.H. C.M.W.O.B.O. M.B.I.M)

Construction Buena Vista

 

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