1960's home DPC

whatsthenews

We had a survey by a cavity wall insulation company today after we got a flyer from local council and 0800 repair offering discounted/free CWI for qualifying households.
We've lived here for a year now and very recently noticed that the top of the block paving to the rear main house elevation appears to be right on the DPC.
I mentioned this to the surveyor and he said that would be an issue re having CWI.
When he's finished his survey we asked him about it and he told us that it has 2 DPC's.
There is a single brick air brick immediately above the DPC where the block paving sits.
Higher up the wall (about 3ft, then maybe 7ft) there are 2 air bricks which are the depth of 2 bricks.He pointed out visible DPC below the lowest of these 2 air bricks, but we can't see it anywhere else in the wall except below this air brick.
On the front elevation the land slopes away to the right , so the DPC is higher up the wall there. The larger air brick on this elevation seems to be immediately above the DPC, with a couple of the smaller ones higher up.
We've talked about it since he left, and neither of us are convinced that having the CWI done is a wise move with the block paving at the level it's at.
Neither do we understand the purpose of having a further DPC higher up the wall as the lower one should stop any damp below the level of the floor joists. We understood that the larger airbricks were to allow ventilation of the cavity but we're no experts and struggling to find anything helpful online so any advice is appreciated.

FreeBear

Some photos would help..
But you are right, the air bricks at 3' and again at 7' would have nothing to do with the placement of a DPC. Far more likely that the DPC is at the same level as the bottom of the door jambs and run either just above or just below the air brick at ground level.

I'd suggest you do a little search for "French drains" and consider fitting one around the perimeter of the house. A weekend or two of work along with a bulk bag of gravel is all that is needed.

By the sounds of it, your property would not be suitable for CWI due to the high level air bricks - Don't suppose the salesman did a cavity assessment ?
It would require a few holes drilled in the wall and a camera inserted to check for debris or cement snots bridging the cavity (usually where the wall ties are).

whatsthenews

thanks FreeBear. Yes, we've looked at the options for solving the BP /DPC issue.
There are no doors on the rear elevation of the main house. The back door comes out of the utility room which is at the back of the garage with a door from the kitchen and into the garage. Cavity wall between house and garage/utility. Concrete floor, flat roof and single brick construction.
The DPC on the garage and utility is a brick above the BP, but the floor level is about 10mm below the height of the DPC
Difficult to work out where the DPC is in relation to the door jamb, but I'll try. Could we measure the height of the internal wall from windowsill to the floor plus depth of a floorboard and then compare measurement to that outside?
I asked about the air bricks and he said they would be sleeved off?
He wasn't the salesman as such. He came 3 days ago. This guy was the surveyor and drilled 3-5 holes on each elevation and put the camera in.
Seemed to know what he was talking about as he said he first suspected that the house was non standard construction with a metal frame as the cavity walls at the corners are extra deep- 180 cm as opposed to 60 cm (assume that's the full wall depth, not just the cavity), but he said he couldn't see any metal in the walls. Apparently we have some metal work up in the loft though.
The surveyor when we bought the house we think mentioned this and may have said that was why we don't have any supporting walls upstairs.Funnily enough he didn't say anything about the block paving though!