Converting an Underbuild

Hello John,
We urgently need larger accommodation and in the present climate realize that it may take some considerable time to sell our existing villa and purchase a new home.   We have also worked out the costs of selling and buying a property that we could afford and feel a better option would be to stay where we are and spend that money on our existing property.
We are considering increasing the size of our villa by adding further rooms in the under build which at present is used for storage.  We are unsure of the regulations regarding this work but feel this may be the way to go,  please give me your thoughts.
Ron & Shirley

More and more people are deciding to alter their existing property to cater for their needs rather than going to the expense of selling their existing home and buying a new one. Simply buying a new property will cost you in the region of 10% of the value of the property and on an average villa that could be 30 – 40,000 euro’s, add this to the cost of selling a property and you have a tidy sum to play with. Many people in this area have converted their under build into living accommodation, some with stunning results. I converted our under build in Orba 5 years ago into a one bedroom apartment, not because we urgently needed the extra space but as extra accommodation for visiting family and friends. Numerous home owners in the area let out their under build apartment on a holiday rental basis primarily to the English but increasingly to the French, this can be extremely profitable and would soon pay for the initial cost of the conversion.
Any work of this nature should have a building license and dependent on the size and complexity may require a project. The main building regulation requirements you should consider are room heights which should be 2.5m (8 feet), damp proofing and insulation.

Room heights
In Spain the minimum room height for any habitable room is 2.5m this is 200cm (8 inch) taller than the English Building Regulations for habitable rooms in basements. Most Spanish under build projects fail at the first hurdle when it comes to room heights but this need not have to be the case. The required room height can be achieved by simply excavating out the under build floor if by doing this you are not undermining the existing foundations or creating unnecessary stress on the existing walls. Even in extreme cases it might be worth underpinning the existing foundations where necessary, this may not be as expensive as you might first imagine. It is important when considering any structural work of this nature to employ a competent professional builder, there have been numerous reported cases of cowboy builders merrily digging away under someone’s property to suddenly find that it is around their ears.

Damp Proofing
Spain is generally considered to be a hot dry country and this is the case in the summer months but when it does rain, it rains; therefore it is extremely important to get the damp proofing right. As many home owners have found to their cost, water will find its way into an under build where there is the slightest imperfection in the damp proofing. Again damp proofing is generally considered by many local builders to be unnecessary or at the least only necessary below a floor, which could then result in the newly finished under build apartment being inhabitable for six months of the year.

Generally insulating an under build or extension is one part of a building project that should not be overlooked or economised on. Insulation is relatively inexpensive to buy and install on a new project and can pay dividends in years to come. By insulating you not only reduce the heat loss in the winter months but also keep the rooms cool in the summer months, not to mention the financial savings due to the ever rising cost of fuel. I am being asked more and more, especially by the age group 55 plus, on how they can improve the insulation in their home as they are now feeling the cold in winter. If you do decide to carry out this work my advice would be double the minimum thickness of insulation required by the building regulations, there would be very little increase in the overall cost of the project and the long term savings would be significant and this would certainly increase your level of comfort.

I hope the above comments have been of assistance in helping you come to a decision on whether to convert your under build however, if there is any specific question you may have just give me a call.

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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Construction Buena Vista
Urb. Palmeria. Orba 03790


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0034 965 577 464 (office)


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Buena Vista Villas s.l.

Urb. Palmeria. Orba 03790


Please call us on


0034 965 577 464 (office)


0034 629 554 561 (mobile)


Or simply click the image above