DPC in Single Skin Block Workshop

[Skavenger]

Hi,

I am building a 3 x 2m workshop consisting of breeze block walls about 3 - 4 courses high on top of which will be a wood clad timber frame and a fibre glass roof.
Two block walls are already in situ and I have just laid the footings for the remaining two new walls.

Should I add a DPC to these walls? If so where should it be laid and how do I fit it.

I have seen DPC rolls in Wikes about £8 for 30m

TVM

 

[Red_Shift]

If you are building a wooden structure on top why don't you either put damp proof course between wood and block or alternatively add an extra course of blocks with damp proof course to stop moisture rising to your wood?

 

[Skavenger]

If you are building a wooden structure on top why don't you either put damp proof course between wood and block or alternatively add an extra course of blocks with damp proof course to stop moisture rising to your wood?

I was going to lay a single course of block on my new footings the top of which will be just above ground level. I was then going to place a DPC here before I lay the second course of blocks? The only issue is that there would be no DPC on the two existing walls?

 

[^woody^]

The concept is that a DPC goes at least 150mm above external ground level, and at the same level as the internal floor, and then a DPM under the floor is tucked onto the DPC before the walls are built up further. What this does, is provide a complete barrier to water coming up the wall and up through the floor.

On a single skin wall a DPC does nothing to stop water coming down or across the wall above the DPC level.

So, if a wall has no DPC, or is going to be prone to water coming across it anyway, then if internal dryness is important, then the walls will need to be lined internally with a suitable barrier, or rendered externally.

 

[Skavenger]

I was not intending to render the walls but if it will help with the damp then I may. I was contemplating battening the walls inside and lining with OSB with cellotex in between but I won't do this unless there is enough space internally.

So I guess I'll put in the DPC in my new walls and then it's there if I decide to render which I probably will to help keep the inside dry. I'll have to think about the existing walls though?

I have already bought a membrane for the floor so now I know how to link them - thanks.

Here's where I think the DPC will go (as long as its 150mm), otherwise it may be higher and skip the door frame?.

 

[Skavenger]

I have just watched a video on laying a DPC but on a brick wall. I assume the process is the same for a block wall?

1. Mortar the top of the block course.
2. Lay on the DPC
3. Smooth out with the back of a trowel leaving aprox 5mm mortar under the DPC
4. Mortar on top of the DPC and lay next course of blocks as normal

Is this correct?

 

[23vc]

That's what I did, where (1) is a thin bed

 

[Skavenger]

That's what I did, where (1) is a thin bed

Ok thanks.