Q I have an ongoing problem with a sink in an en-suite bathroom of a rarely used bedroom; for whatever reason a foul smell is emanating from it. It seems particularly bad in the evening and can be smelt downstairs which can be embarrassing when we have guests. I have tried pouring bleach down it but that only worked on a temporary basis. Given that the sink and room is used irregularly what do you think is the problem and how can I address it?

A Initially you need to check three things; 1) Is there a trap under the wash basin connected to the waste pipe, 2) Is there a blockage in the drain, and 3) Is there a vent to the sink waste pipe?

The problem is most likely due to faulty or incorrect plumbing where a draining of the water seal to the waste pipe trap under the sink occurs. The “U” shaped trap (either an “S” trap or a “P” trap) holds water and is in effect a seal against foul gases back flowing from the sewer and entering the bathroom. If the trap is empty for whatever reason the gases bypass the trap and cause a foul smell in the room.

This occurs when an appliance is flushed, usually at a lower level, and draws out the air from the soil pipe and eventually the water out of the appliance trap above where there is insufficient ventilation to the drainage pipework system.

If there is no vent provided to the appliance there is nowhere for the back-flowing gases to go. Even if the main drain is vented, a unit at the end of the line may be too far away from the vent pipe and be affected by air starvation. In this case an additional vent is required to alleviate the problem.

It is a relatively inexpensive repair but forming a hole through an outer wall or roof for a vent pipe may look unsightly initially until you get used to it.

If the trap is shallow water it could evaporate over time. Running the tap occasionally could sort that to refill the trap and maintain a seal. Other rule-it-out checks could include: Is there stagnant trapped water in the overflow chamber? Is there something stuck in the sink waste outlet?

If all else fails call out your local qualified plumber.

Pat McGovern is a member of the Society of Chartered Surveyors Ireland (SCSI) Building Surveying Professional Group

Is roof-first best when renovating?

Q I am currently considering a number of renovations to my home. For a start I am considering installing a number of windows and doors as well as re-roofing the property. Is it true that the roof will need time to settle? If so would it be better to re-roof the property first and then install the windows and doors afterwards to avoid a situation where they do not fit correctly.

A The first consideration is the age and condition of the property. Under normal circumstances a house will settle in the first five to 10 years after its construction. This is mainly due to its drying out and use. This will manifest itself with small hairline cracks.

Any other factors or defects will usually indicate a more serious problem. For example, bulging walls, large cracks, cracks running from top to bottom through wall opes. In an older property, openings formed for windows and doors can often fail due to the wall structure (ie lintols or supports failing) as against a defect in a window or door. Neither are employed as a structural element. Quite often in older properties it is normal to brace wall openingss temporarily to help stiffen the walls during construction such as demolitions or other refurbishment works.

The second consideration is the construction of the house. A good understanding and knowledge of the construction is essential. From your question it is assumed that you are making new openings externally as against replacing older windows and doors. In either case it would be prudent to inspect the current structure and assess the existing construction condition. This will determine the bearing capacity of the walls, the condition of the roof and wallplates and the structure underneath, including existing openings. This will also pinpoint or identify any remedial works required to stabilise the building during and after the works. This should be carried out by a professional.

The choice of professional should be based on their experience with similar projects. In the same vein the appointment of a building contractor must be considered with the same criteria in mind. With these facts ascertained it should be easier to determine the sequence of construction and scope of works required to complete the project successfully.

Robbie Patterson is a member of the Society of Chartered Surveyors Ireland (SCSI)

Problem with an attic conversion

Q I had a building survey carried out and this has highlighted that a recent attic conversion does not comply with the building regulations as the windows are not big enough. This will mean further lengthy delays. Should this not have been spotted earlier by the agent/vendor and what, if any, guidelines are there to ensure that these issues can be dealt with prior to properties coming on the market.

A Attic conversions come in two types, the first is the more common, an attic conversion which is purely for storage and not for habitation as it does not meet current building regulations. You often see this marketed as an attic store/attic space.

If the attic conversion is fully compliant with building regulations, it will be marketed as an additional room, namely a bedroom or living room. Often agents will view a non-habitable attic conversion used as a living space because the owners use it as a habitable space and ignore current building regulations.

With respect to the property you were looking at and its recent attic conversion, if it was marketed as a habitable space then the property should have had all the necessary planning documents/certificates of compliance.

As estate agents, it is one of the first questions we ask a prospective vendor when appraising their property and we always ask them to make sure all documents are in order with their solicitor before going to the market. The bad news is that a lot of the time we will not see their planning documents/certificates as they are often with the title deeds which may still be with their banking institution.

Felicity Fox is a member of the Society of Chartered Surveyors Ireland Residential Surveying Professional Group

Send your queries to propertyquestions@irishtimes.com or to Property Clinic, The Irish Times, 24-28 Tara Street, Dublin 2. This column is a readers’ service. Advice given is general and individual advice should always be sought