Damp proofing

[hartley]

The walls at the rear of my recently purchased victorian terraced house have been damp proofed, although I am not sure when. However, at some point following the damp proofing the rear yard has been concreted which has raised the level of the ground to within 1 bricks height of the holes where the damp proofing stuff was injected. Is this damp proofing still effective? I am concerned about rainfall which splashes back above the level of the holes. Also if I wanted to tile the area next to the wall or put wooden decking down (which might make the 'ground' level higher than the damp course) would I need to re-do the damp proofing at a higher level? Any advice? Ta! P.S. Does anyone else think 'proof' is a very odd word? Just say it out loud.... 'proof'...... see!

[maurizio]

With the house did you get proof/insurance of general  works done etc. I once owned a Victorian ground floor flat that I then put up for sale. During the sale process one of the surveys done by the potential buyer found the external walls to be damp. On contacting my leasholder he mentioned that there was a 25yrs damp-proof "guarantee" but it had expired a couple of years earlier. You can immagine how furious I was as I then had to spend almost � 2000 to re do all the wall plus redecorating etc. So check first if you have an insurance somewhere, maybe the previous owners may know. If not, you can call some professionals, it is normally free of charge for a quotation and they will be able to advise you. If you plan to deck the area, you need to leave some space between the walls and the decked floor so air goes through. Not sure if you need to re-do the damp course though.

[gazzawazza]

Hartley, the level of the DPC is important.  It should be a minimum of 150mm (two course) above the ground level adjacent to the wall. 

This is to stop rainwater bouncing off the ground and going over it, (concentrating water at a specific level), as you mention in your post.  But if you re-do the DPC higher up this is also very likely to cause damp problems especially if you have solid walls (which you probably will have).  This is because the damp will travel through the wall and affect the inside surface/plaster etc.  That is the reason why walls are built with cavities nowadays

[booksworth]

Also, the dpc needs to be below the level of the flooring joists, otherwise the wood will start to rot. So I don't think you have any room to manoeuvre.

[gazzawazza]

Bookworth, I don't want to be pedantic but thousands of houses have floor joists below the DPC level, but different construction methods mean that they are safe from rising damp.

Obviously some will be damp, but this is usually because the joists have been built into the walls below the DPC (allowing damp to strike the timbers) whereas latterly the joists were placed about an inch from the walls and supported on "sleeper" walls which should have had some form of damp proofing between the brickwork and the bottom of the joists.