damp proof course in 1903 block of flats

[alex30]

My block of flats and the others on my street are all made with sandstone dating from 1905. Their seems to be a foundation of another stone in the ground below the sandstone. I am thinking this other stone is designed as some sort of damp proof course.Will this be the case and what kind of stone is it likely to be.???

If it is a dpc then this stone should be open to the air. But actually the ground floor flats use this area as a garden between the front wall and pavement and have soil covering this foundation stone. It,s original design was maybe not a garden but a shallow gravelled area allowing the dpc to breath.

Has anyone come across similar senarios and again what type of stone is likely to be in the foundation and is it dpc???

Thanks

 

[Blagard]

A photograph would be useful. The problem is that in a building of that age all sorts of details may have been used in construction.

From what you describe, the local ground levels have been raised with topsoils or similar which is a risky thing to do with any building. More to the point is do the ground floor rooms suffer from dampness in the walls? If they do then one of the first things to do is to try and get the ground back to original levels, at least locally.

 

[^woody^]

Masonry buildings of that time may or may not have a slate DPC at floor level, or more commonly would rely on the moisture resisting properties of a non porous stone below ground level. They don't need to be open to the air to work.

The stone could be anything. Usually what was available locally.

 

[Blagard]

--snipped--Masonry buildings of that time may or may not have a slate DPC at floor level, or more commonly would rely on the moisture resisting properties of a non porous stone below ground level. They don't need to be open to the air to work.

But bridging any construction intended to protect against dampness should be avoided.

 

[^woody^]

--snipped--Masonry buildings of that time may or may not have a slate DPC at floor level, or more commonly would rely on the moisture resisting properties of a non porous stone below ground level. They don't need to be open to the air to work.

But bridging any construction intended to protect against dampness should be avoided.

Nothing is bridged. The OP states that the ground covers the different foundation stones. Those stones are not acting as a DPC, they are merely stones used for the foundation. They would be selected to be impervious, or less pervious than sandstone and would perform the same whether exposed or not.

It's exactly the same principle as when solid engineering bricks were used up to floor level without a physical DPC. And those engineers were in the ground.

 

[Blagard]

"It,s original design was maybe not a garden but a shallow gravelled area allowing the dpc to breath. " I took this to mean the ground levels may be raised

Woody can you be sure! - "Nothing is bridged" ?

 

[^woody^]

I can be sure that a DPC is a single physical barrier which would typically be at or near floor level. And yes, that should not be breached by the ground.

But a whole lot of stone used below floor level in the context of the OP's situation would not be acting as a DPC (despite possibly performing as one) and it would not matter if they were covered or not. Their impermeable properties would be the same whether covered or not.

Its best not to think of them being a DPC as referred to by the OP. They are just foundation blocks.

 

[Blagard]

Woody we seem to agree that the stone or whatever below ground does not need to breath. The very nature of DPC's or materials suitable is that they are impermeable.

As to a DPC - there probably is not one in the modern context, but as you say an impermeable material has just that effect similar to engineering bricks.

If that impermeable layer ends up being buried it ceases to have any DPC function on the construction above. So long as the OP has concerns that the garden levels may be changed bridging remains something to be considered.

Not mentioned is the other potential issue.
The purpose of having a DPC 150mm above ground on external walls is to overcome the splashing effect of rain that can soak adjacent vertical surfaces. Not generally a problem in modern construction if the material above is frost resistant, but on older properties not having a separate inner wall leaf this can lead to dampness in the wall on the internal face. So again ground levels can play a part if the walls above are constructed in a way that will allow passage of water. (Not just the stone, but whatever they are bedded into)

So while you consider nothing is bridged, I remain uncertain and in any event believe attention should be given to ground levels and go from there.