Foundation tar?

[simonb88]

My 1939 bungalow in Glasgow has some sort of tar damproofing on the foundation floor??

I'm trying to figure out how to stop the dampness as all this stuff is either missing and patches or has gone soft and cracked - especially where it meets the walls. I suspect when built this was just poured in to form a liquid DPM over the earth below.

Can I buy this stuff and just pour it over the worse cracks etc? Or should I just cover the whole area with plastic DPM sheet?

Cheers.

 

[freddiemercurystwin]

Don't really understand the issues.

 

[hotrod]

I think simon is referring to an asphalt floor finish. I suspect the 'earth' is maybe a perished concrete substrate although I am only guessing......

Pics would help clarify the issue.

 

[simonb88]

I haven't really dug right down under this tar material until I hit concrete. Best way to describe it is like black toffee...? But in some places its quite damp but maybe thats coming through the concrete below.

No idea how this house foundation was built and what all this black stuff is. Which after 70 years is breaking up revealing moist soil underneath.

I'm really interested in how to recover this area as my humidity is quite high 85%-90%. Was told that DPM sheeting could be used. Think I'd need gallons of the modern equivalent of that black stuff?

 

[Alastairreid]

Solum Treatments

The solum of a property is the subfloor base of the property (level under ground floorboards). In older properties built prior to the 1950’s normally the solum areas are unsealed and are possibly damp. This may be due to the solum being lower than the surrounding ground levels around the property, the water table being near the solum level, Defective or ineffective land drainage in the area etc .

Most properties built since the 1950 had the solum areas sealed, earlier with bitumen tar or in later years moving to current building standards which stipulate that a Heavy gauge Polythene Damp proof membrane (DPM) be laid on top of aggregate and covered with a screed of concrete. Many of the old tar sealed solums have deteriorated and the tar has broken down and is in need of replacement.

A high moisture content in the subfloor area from a damp solum can result in the following:

High levels of condensation/mould growth throughout the ground floor living area
Wood rotting fungi affecting, floor timbers, adjacent skirtings/joinery timbers

Barring digging out the solum and re-doing it with the modern equivalent ie hardcore,sand blinding,dpm and concrete.

Alternative is to patch with cold tar.

 

[simonb88]

Thanks. That clears up whats going on under my floor.

But where can you buy cold tar. Hopefully it comes in 25ltr cans.

 

[Alastairreid]

How are you going to access the solums?

Last time we done this was probably around 30yrs ago and the floors were lifted including joists.

We used blocks of tar and a tar boiler, applied using watering cans. Not a diy job.

 

[simonb88]

The house is on a slope and I have a walk in basement at the back and can almost crouch/stand every where else. But no way I could transfer hot tar around under there. Got too much retaining walls to climb through. I was thinking of using Black Jack liquid DPM anyway as cold and in tin?

At least now I understand how it was done in the old days. I'll have to get heavy gauge DPM and lay that down. Bricks will have to be put around the edges to hold it down.

Thanks for the reply.