Damp issues in my new flat - French drain or reduce ground level or both?

TranceNRG

Hi everyone,
I have some damp issues (though not huge still annoying and I see paint bubbling up in some areas) in my ground floor Victorian flat (I think - built in early 1900s). When I had the building survey done, it highlighted the ground level at the back of the house being too high. I have a patio made up of bricks on one side and concrete blocks on the other side of the building.

Recently I decided to get my garden done and at the same time do something about the damp issues. I've had a few quotes from landscape gardeners for following options:

1. Leave the current patio but dig out around the house and install a french drain

2. Remove the current patio, dig out further and build a new patio with sandstone plus a french drain around the house

Option 1 costs about 2K and option 2 costs about 5.5K (both options include clearing the garden, laying turf and creating flower beds).
Obviously option 2 will look much nicer and it will add more value to the house but having done a full refurbishment, I am still under a bit of financial pressure so it's not an easy decision.

However if I go for just a french drain (option 1), I don't want to later find out, it hasn't solved the problem.

I know there's a lot of people here with experience/knowledge in damp problems and how to prevent it so would love to hear your opinion on what would work in my situation.

Will I be able to get away from having just a french drain (but higher ground level)?

If I go for reduced ground level and new patio, do I still need a french drain? Could I get away from not having a french drain? I wonder not having to install a french drain will save much money?

Thanks in advance for any input.

anselld

Is there a visible damp proof course and does the proposed new patio level come comfortably below that DPC?

TranceNRG

Hi anselld, no the damp proof course is not visible. Is it possible that there was no DPC installed?

I think the new patio will be 10cm+ lower than the current level.

Mr.Generous

On a victorian build you wont see a dpc, it was generally done with layers of slate. 100+ years later its never going to be fully effective. The chemical stuff you inject into the mortar has been 100% effective for me, but doing it requires plaster off to 3ft / 1mtr and re plaster with a damp proof mix of plastering sand, cement and chemical additive.
Anything done outside will help, but probably not cure entirely. If the ground level or patio is too high outside this would be my first job, I'd hate to do the damp work and not give it a chance. Are your floors downstairs timber or solid? Seen hard floors put in that draw damp too.

Apodemus

With a Victorian Property it is quite possible that there is no DPC. What is the construction - brick or stone? French drain or ground level at least 6 inches below the joist ends is probably the answer (don't get suckered into any expensive pseudo-solutions without doing a lot of research into their validity).

Properly done each of your options should provide a solution but the lower ground level should be more certain and more likely to be permanent.

If I were you I would join the period property forum (https://www.periodproperty.co.uk/forum/index.php) and ask the question there - stacks of threads on exactly this situation.

ThemeOne

Any property built before 1935 might not have a DPC, it depends on area and builder really.

TranceNRG

Thanks for all your input so far. In answer to one of the questions, tt's a brick house. Having recently done a full refurbishment it's not an option to hack off plaster and do any damp proofing work inside.

I will ask the question in that forum

If I do go for the new patio with lowered ground level, will I still need a French drain around the house? or is that unnecessary once the ground level is lowered?

G_M

My property is 1851.

If I lift a ground floor floorboard I can see the floor joists, and walls, are sitting on slate. This acts as a dpc. From outside you can't see anything.

I also had a damp problem originally as previous owners had built up a beautiful rockery against the front wall. Removed that and dug a ditch about 1 foot wide along the exterior wall. About 2 foot deep and half-filled with gravel.

I'm sure that does not comply with current standards but

* very little in this house does comply and
* no more damp so who cares?

Apodemus

G_M wrote: »

My property is 1851.

If I lift a ground floor floorboard I can see the floor joists, and walls, are sitting on slate. This acts as a dpc. From outside you can't see anything.

I also had a damp problem originally as previous owners had built up a beautiful rockery against the front wall. Removed that and dug a ditch about 1 foot wide along the exterior wall. About 2 foot deep and half-filled with gravel.

I'm sure that does not comply with current standards but

* very little in this house does comply and
* no more damp so who cares?

What you did sounds perfectly correct to me. Unfortunately all too often people spend huge amounts of money on all manner of internal solutions that may mask the problem for a few years but don't actually solve the problem! I fell foul of this myself by following the mortgage conditions on my property, before I learned more about old buildings.

TranceNRG

G_M wrote: »

My property is 1851.

If I lift a ground floor floorboard I can see the floor joists, and walls, are sitting on slate. This acts as a dpc. From outside you can't see anything.

I also had a damp problem originally as previous owners had built up a beautiful rockery against the front wall. Removed that and dug a ditch about 1 foot wide along the exterior wall. About 2 foot deep and half-filled with gravel.

I'm sure that does not comply with current standards but

* very little in this house does comply and
* no more damp so who cares?

Hi G_M, so that's like a french drain right? Do you think this would be sufficient to reduce the moisture going in to the building? I mean my current patio looks OK (though a new sandstone one would look much nicer but it's also about 4K more expensive) but I don't want to spend the extra money and get the ground level lowered and a new patio and a french drain if I can simply keep the current patio and install a french drain.

I think the chap mentioned removing a row of bricks along the wall in the current patio to create the french drain. So that would be about 15cm wide. Would that be enough?

And finally, if I do decide to have a new patio and get the ground level reduced, will I still need a french drain along the walls of the house?

david1951

There is an element of trial and error. The first place to start would normally be the cheapest option (dig a ditch and put some gravel in) and go from there.

I'm no expert but I think a French drain would be the ditch + gravel but also an underground pipe buried in the gravel that collects water flowing into the drain, and takes it away from the house.

There is no silver bullet but often the simplest solution can be the most effective.