Slope Stability Assessment

TTM

Has anyone ever had to have a slope stability assessment carried out as part of a house purchase?

We've just had a report back from Terra Firma recommending an assessmant because the house is in an area susceptible and based on their BGS mapping. Our survey didn't flag any issues with movement and I'm just trying to work out if this is really needed, so I'd be interested to hear from anyone who's been in a similar situation.

Section62

TTM said:

Has anyone ever had to have a slope stability assessment carried out as part of a house purchase?

We've just had a report back from Terra Firma recommending an assessmant because the house is in an area susceptible and based on their BGS mapping. Our survey didn't flag any issues with movement and I'm just trying to work out if this is really needed, so I'd be interested to hear from anyone who's been in a similar situation.

Is any part of the property (house and garden) on a slope, or are there any slopes or retaining walls on nearby property?

TTM

The house is on a hill, yes.  It's in Stroud, which is nestled in amongst five different valleys I believe, so hard to avoid hills!

Is this a fairly normal extra survey to have to pay for if you're buying a house somewhere like that?

canaldumidi

It's the immediate surroundings that are key surely?

Is the back of the house higher than the front (or vice verse? Is the garden on a slope? Sliding down towards the house's external walls (or vice verse?)

Are the neighbours' houses or gardens higher/lower than yours?

Then how old is the house and does it show any signs of movement? Cracks in the walls that have been repointed? Window lintels or cills not horizontal?

TTM

canaldumidi said:

It's the immediate surroundings that are key surely?

Is the back of the house higher than the front (or vice verse? Is the garden on a slope? Sliding down towards the house's external walls (or vice verse?)

Are the neighbours' houses or gardens higher/lower than yours?

Then how old is the house and does it show any signs of movement? Cracks in the walls that have been repointed? Window lintels or cills not horizontal?

As stated, it’s on a hill, so some houses are higher and some are lower.  The garden is uphill of the house and does slope slightly.  Again, the survey didn’t flag anything of concern with regards to movement.  The property is a Victorian semi, so it’s been around a while and hasn’t slid down the hill yet. 

I’m just interested to hear if anybody has had something similar flagged during searches and whether they did spend the money on an extra geological survey.  A brief google stated it may cost 1500-2000, so not an insubstantial cost on top of the L3 we’ve already paid for, so want to make sure it’s worth paying for if possible. 

canaldumidi

TTM said:

canaldumidi said:

It's the immediate surroundings that are key surely?

Is the back of the house higher than the front (or vice verse? Is the garden on a slope? Sliding down towards the house's external walls (or vice verse?)

Are the neighbours' houses or gardens higher/lower than yours?

Then how old is the house and does it show any signs of movement? Cracks in the walls that have been repointed? Window lintels or cills not horizontal?

.... The garden is uphill of the house and does slope slightly.  ..

If the 'slight' slope is genuinely slight I wouldn't worry. If it were steep I would. But what is your definition of slight'?

Woolsery

TTM said:

The house is on a hill, yes.  It's in Stroud, which is nestled in amongst five different valleys I believe, so hard to avoid hills!

Is this a fairly normal extra survey to have to pay for if you're buying a house somewhere like that?

No. I'm originally from Bath, which is similar, and I've lived in many houses there, renting and as an owner. The oldest was one of the grand Georgian terraces and the youngest 1970s.

The only house I knew that had issues with the S word was the 70s property. The slope wasn't extreme, but it was on clay and there were springs which apparently lubricated the foundations sufficiently to enable the front wall of the property to move downhill relative to one of the side walls. This was noticeable from inside and outside the house and didn't need a specialist survey to spot, just keen eyes. Fortunately, we were only renting this house between moves, and we soon discovered it was forbidden to discuss the 'S word' on that estate! Not all houses were affected by any means, but it was probably something experienced local surveyors would have known about and looked out for.

Despite the above, the house sold for close to the 'normal' price for that area, but not during our tenancy. I imagine it was underpinned when a large extension was added. It was £465k when we left and I'd guess it might be over £800k now going by recent sold prices!

Section62

TTM said:

canaldumidi said:

 A brief google stated it may cost 1500-2000, so not an insubstantial cost on top of the L3 we’ve already paid for, so want to make sure it’s worth paying for if possible. 

Tell the surveyor what Terra Firma said, and ask them to comment on the need for the assessment to be carried out.

If there is nothing immediately adjacent to the property which might cause concern then the risk may be at macro level - e.g. a situation like Woolsery's.  If the ground conditions are 'just right' something like a slip circle failure can occur when there was no previous indication of problems with ground stability.