1930's Footings, how much to expose?

[Safety First]

I did post about this in the past, but assumed that there would be more than one brick under DPC and over footings. Having dug out now, I can see that to get the depth under DPC, i'd expose the footings...

Previous owners had concrete poured over DPC to make driveway. Substantial woodworm to adjacent floor boards.
Now digging down with plan to fill with washed gravel, but to what levels?

The bituminous strip is on top of a single brick over footings, which are large stones.

If I expose the footing stones, might they shift over time and should I point them?

I am uncertain about making a french drain- I cannot see water pooling, so is this not of use?

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• Safety First
• 30 Mar 2015
• 1

 

[r896neo]

You ideally don't want a french drain alongside shallow footings as it could in theory undermine them by washing material away. In reality you'd need a bit of a flow for that to happen but worth considering.

In the past In this situation i have sythaprufed the wall and filled the gaps with gravel and laid the paving 4'' from the wall falling away from the wall.

There is not a lot more you can do without considering tanking the wall internally.

 

[Safety First]

Ok thanks, perhaps I should get someone in whose advice I can pay for and who is insured to specify etc. Any thoughts as to who that is?

Does it follow then that the concrete was action to prevent shallow foundations being washed away?

 

[r896neo]

I don't imagine the concrete was anything more than a surface finish.

The footings won't be washed away unless you actually introduce a flow or a consistant run off of water.

By falling the finished surface away you limit the water ingress to direct fall and or water driving against the wall.

It is worth considering covering them though for good measure.

1 brick below dpc should be ok anyway.

Preventing damp in a solid wall is more to do with sounds pointing and brickwork than a dpc.

A building surveyor might specify it but i'm not sure.

 

[JohnD]

I once synthaprufed a similar wall down to the footings, after repointing, but was later advised that this does not keep the brickwork dry, because the underside of the bricks is still in contact with moist earth.

I was a bit sad to see how much mortar had disappeared and been replaced by mud.

 

[theprinceofdarkness]

As I see it , footing have a downward pressure on them and it is normal for this pressure to distributed into the soil at an angle of 45 degrees. So if you dig down at the side of the footings you get into this area where the soil is carrying the weight of the house and the footing will start to move. However if you do not excavate beyond the base of the footings they should remain stable. Think of cellars.
How high is the concrete over the DPC, your picture does not seem to show it. Also are you sure that you have reached the base of the footings ? .i.e. poked a crowbar under the footings at an angle, to make sure that there are no further courses of stone? even in stone built houses the footings are wider at their base then at their tops.
Frank

 

[Safety First]

..... Also are you sure that you have reached the base of the footings ? .i.e. poked a crowbar under the footings at an angle, to make sure that there are no further courses of stone? even in stone built houses the footings are wider at their base then at their tops.
Frank

Sorry for misleading in this respect; no the footings are indeed about a 18"deep. Pic attached. I replaced timber floor to kitchen this week. DPC sits above one brick which is bedded onto footings. Footings are built into the room by about 9" stepping down on the way.

So I haven't exposed bottom of footings.

Would then a good plan be to
1. remove concrete bridging DPC.
2.Remove render to 6" above DPC.
3. Fit bell cast at that line.
4. Point lime mortar to any exposed footings that need it.
5. All with aim to leave as much firm soil around footings as possible.
6. After summer drying out, synthaproof exposed brick above DPC and below bellcast, or would I synthaproof right down and over DPC to cover first brick on footings?

Trouble is it's a west facing wall that does get driven rain. I have no real sense of what type of protection from 'washing away' that footings will need.

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• Safety First
• 31 Mar 2015
• 1

 

[r896neo]

Th synthapruf is not to keep the brickwork dry it is to stop rain penetrating the small area of brickwork that is exposed and above the dpc.

Don't obsess over the washing away, i just mentioned it to make sure you didin't try to fall all water into the channel and create a french drain there to flow water away.

In my opinion you could cover with paving concrete or whatever up to the base of the brick course under the dpc.

Render as you have planned with bell-cast and then either synthapruf or use a modified thin coat type render over the bricks below dpc.

I would imagine it will be difficult to find anything that will last well though.

 

[Safety First]

Thanks for that...

In my opinion you could cover with paving concrete or whatever up to the base of the brick course under the dpc.

What about pointing to any footings that appear to need it on exposing the DPC brick, then covering with gravel-chippings? The drive/concrete currently falls away from the house.

I suppose I'd best have a membrane- slate? DPM? from under bellcast, down below current DPC, with the concrete filled back in against wall?

The drive as was (before I cut a chase in it) sent water away from house, but also bridged the DPC...