There’s an unpleasant smell in my garage. How can I fix it?

Property Clinic: I have been unable to determine what is causing this smell

Whilst water coming up through a floor may not be noticeable to the eye, it can give rise to a foul odour. Photograph: iStock

Whilst water coming up through a floor may not be noticeable to the eye, it can give rise to a foul odour. Photograph: iStock

 

I have three garages at the bottom of my garden, two of which have been amalgamated to form one and the other has not. All three have had a new roof (Nordman sheeting) fixed. When this upgrade took place, new ceilings including insulation and plastering to walls was carried out and a new concrete floor poured. A very successful job at the time.

Over the years one of the garages (two that were knocked into one) has developed a very unpleasant (damp like) smell. I have been unable to determine what is causing this. Could you please help me to remedy this problem?

This is a fairly open question and is difficult to answer without knowing more about the sheds. Given that the issue is related to a damp-like odour, I would start by looking at the potential sources of dampness. One of the primary functions of the building is to provide shelter from the external elements, but if there are defects in the external fabric then water can penetrate from the exterior.

I note that when the sheds were upgraded, they were reroofed, and one would hope that the roof was well done. I also note that the roofs were covered with Nordman sheeting and given the sheet-like nature of this type of covering, there are very little joints and thus very little risk of leaks through the covering.

However, the valley/intersection at the junction of the two interconnecting sheds could well create a high risk for a localised problem with water penetration as it can be prone to filling up with leaves/debris and ultimately to blockages etc. This should be checked out and cleaned/repaired as necessary.

I also note that a new floor was provided when the sheds were being refurbished and again one would hope that this was done well. It would have been important to incorporate a damp-proof membrane in the floor to prevent water/moisture coming up through the floor.

While water coming up through a floor may not be noticeable to the eye, it can give rise to a foul odour. This can be an issue if/when a shed is built on an external yard/hardstanding, as external hardstandings would not incorporate any form of damp proof membrane. Furthermore, if the floor is at or below the surrounding ground level, you can have an issue with occasional flooding/water penetrating in at this level.

The external elevations could give rise to a risk of some water penetration particularly at the window and door/wall junctions and/or at the floor/wall junctions. Basically, if water gets in even in small quantities, this will give rise to the type of smell that you are experiencing so it is important to check the external fabric to ensure that there are no leaks arising through this.

I am not sure if there are any plumbing devices within the sheds such as a water tap. If there is, then for the avoidance of doubt the installation should be checked to ensure that there are no leaks emanating from this.

Finally you should consider the level of ventilation to the shed. A poorly vented space can also give rise to a damp foul odour and this can be a problem with sheds which are seldom opened up and not getting the benefit of regular air movement. A well-used shed will be naturally vented simply by opening the door regularly. But if the shed is not being used regularly, you should consider installing a window and leaving this partially open.

If, however, the shed needs to be secure, then you could consider a suitable ventilation grill that will allow ventilation without compromising security.

I have covered a variety of potential issues in an attempt to identify all possible causes however an inspection from your local chartered building surveyor would be able to pinpoint the problem and they will be able to advise on the specific cause and the necessary works required to address the problem.

Val O’Brien is a chartered building surveyor and member of the Society of Chartered Surveyors Ireland, scsi.ie

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