Position of damp proof course

[microbe]

I have a concrete base and am now constructing a timber frame. I would like to add a DPC but wondered if this is best located between the concrete and the frame, or the frame and the floor.

Any suggestions

Adrian

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[oldpink]

if you put it above the timber you have the chance of the timber getting wet and rotting
having worked on building sites for a bit damp course would go 1 or 2 layers of brick below the floor level
though I was fitting kitchens not building the houses

[Paul M]

As old pink says, you need to be careful with Damp Proof Membranes they can trap moisture and cause rot.

If you put a membrane between the joists and the flooring water will get between the slab and the joists and sit there forever.

I'd be looking to keep the water off the slab by having the side wall paneling/boarding overhanging the concrete by a couple of inches to keep it dry. 

That way a membrane shouldn't be needed.

If it was mine (as an ex wood butcher) I'd design in some airflow routes round the joists. There's nothing better than a draught for curing damp!

[Tinker1947]

Its normal to put the DPC between bricks so the cement gets to grip it both sides..

[moriniboy]

If it was my build I would use further timbers at 90 deg to the current ones to allow air flow to the underside of the floor, then place 100mm DPC between the new timbers and the concrete.

I'm also assuming that you are using treated timber?

[laser_jock99]

I would raise the frame off the base entirely on few concrete construction blocks. Put a thick piece of plastic (eg a slice of a 5L container) between each block and the touching wood joist. That way you get above any damp, put a barrier between the porous block and the frame and have the circulating air gap required to keep it drying.

Raised blocks & airgap on my obsy

[todd8137]

I never did put a damp proof course in ,Why because the guy that made my custom made obsy shed said he had a shed he keeps reptiles in he tried every thing in the end he built a new shed and put a layer of fixa foam under the shed I did this and have had no problems with any thing

Pat

[microbe]

Thanks for all of your suggestions. I have now modified the base to allow for plenty of ventilation, but will also incorporate a mesh to prevent the nesting of rodents from the neighbouring field

I'm also assuming that you are using treated timber?

Yes, I'm using tannalised, but also adding an extra coating of preservative for good measure.

[laser_jock99]

Thanks for all of your suggestions. I have now modified the base to allow for plenty of ventilation, but will also incorporate a mesh to prevent the nesting of rodents from the neighbouring field

I'm also assuming that you are using treated timber?

Yes, I'm using tannalised, but also adding an extra coating of preservative for good measure.

Mice will get in anywhere- I've just found they've eaten the saddles off the bikes in an adjacent shed this winter. I need to check my under floor cables......

[Steve T Dawson]

I have a concrete base and am now constructing a timber frame. I would like to add a DPC but wondered if this is best located between the concrete and the frame, or the frame and the floor.

Any suggestions

Adrian

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do both

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[Digz]

In this situation a DPC should go ontop of the concrete with the timber sole plate(s) ontop. Your DPC should also be a minimum if 150mm above external ground level.