Damp proofing basement - how far do I need to dig down

v638sg7k1a92bx

Tenant has moved out of a retail unit they were renting for 15 years and I'd like to damp proof the basement now that they are gone.

How far do I need to dig down to damp proof the basement floor to put membrane etc. Does 40cm seem sufficient?

GreeBo

Where are you thinking of digging down?
Presumably the outside walls?

How are you planning on damp proofing? What are you going to apply to the walls? Have you thought about a weeping tile + sand + pea gravel etc?

my3cents

GreeBo wrote: »

Where are you thinking of digging down?
Presumably the outside walls?

How are you planning on damp proofing? What are you going to apply to the walls? Have you thought about a weeping tile + sand + pea gravel etc?

I guessed he was digging down 40cm below the current floor level INSIDE the basement?

Calahonda52

my3cents wrote: »

I guessed he was digging down 40cm below the current floor level INSIDE the basement?

As did I, my concern is how far down is the winter water table

GreeBo

If it was me I'd be doing both...wouldnt like the idea of allowing the walls etc to get soaked and then hoping it doesnt make it into the interior.

Anything I have ever seen about waterproofing (albeit typically in the US & Canada) they always go outside with several membranes finishing with a solid one designed to keep the water physically away from the wall.
They then add in a weeping tile to take the water from the membrane away from the house and into the drainage system.

policarp

Bria Jolly Ubiquity wrote: »

Tenant has moved out of a retail unit they were renting for 15 years and I'd like to damp proof the basement now that they are gone.

How far do I need to dig down to damp proof the basement floor to put membrane etc. Does 40cm seem sufficient?

You can damp proof the floor no problem and insulate it, but the problem is with the walls.
If they don't have a DPC (Damp proof course.) they will be subject to rising damp. So unless you do both jobs at the same time you will still have a damp problem.

GreeBo

policarp wrote: »

You can damp proof the floor no problem and insulate it, but the problem is with the walls.
If they don't have a DPC (Damp proof course.) they will be subject to rising damp. So unless you do both jobs at the same time you will still have a damp problem.

they'd need more than a dpc since the walls are underground for a basement

my3cents

I think everyone is over thinking this?

If the basement is relatively dry then there is some advantage to just damp proofing the floor. Its not going to be perfect but it will be a small improvement and allow a better floor to be put down. The walls will probably remain as damp as they are now but that may not be an issue.

GreeBo

Its a fair point...OP what area you planning on using it for afterwards?

v638sg7k1a92bx

my3cents wrote: »

I guessed he was digging down 40cm below the current floor level INSIDE the basement?

Correct but why do you say 40cm, is that the standard?

v638sg7k1a92bx

policarp wrote: »

You can damp proof the floor no problem and insulate it, but the problem is with the walls.
If they don't have a DPC (Damp proof course.) they will be subject to rising damp. So unless you do both jobs at the same time you will still have a damp problem.

I'll be doing both the floor and walls but if I dig down then it's gong to be about 10cm of concrete to remove and another 30cm of dirt if I was to go 40cm.
40cm is a huge amount of dirt to dig and dispose of.

my3cents

You mentioned 40cm. Its a lot to remove and of course to replace but you will probably want to include insulation in the floor which reduces the amount of concrete a good bit.

v638sg7k1a92bx

my3cents wrote: »

You mentioned 40cm. Its a lot to remove and of course to replace but you will probably want to include insulation in the floor which reduces the amount of concrete a good bit.

I’d rather forgo the insulation than try and get rid of 40cm of dirt.

my3cents

Do you even need to dig out? If you have enough head room can you put a new floor over your current floor?

v638sg7k1a92bx

my3cents wrote: »

Do you even need to dig out? If you have enough head room can you put a new floor over your current floor?

Considering that aswell thanks.