House with wattle and daub plus brick - Black jack question please

[laudan]

Newbie here seeking advice please. We live in an old cottage (C.1750) that's timber framed, mostly wattle and daub with brick on the outside - the brick has a lower coating of blackjack (applied by a previous owner). Unfortunately a previous owner installed a tarmac style driveway resulting in the outside flooring level being a lot higher than the internal floor. Since we moved in we've had very high levels of humidity and damp on the ground floor walls and so are currently in the process of removing tarmac/soil and have dug deep enough to expose around 2-3 bricks below the blackjack where there is then another coarse of bricks that juts out slightly (possible foundation from when the bricks were added?). Hopefully this removal will help the walls to start to dry out, however my question is whether we eventually should be applying blackjack to the now exposed lower bricks or would this cause more problems and trap moisture in? Advice welcome please, thanks

 

[Cubist]

(possible foundation from when the bricks were added?)

That is indeed the foundation, or more correctly the footing, for the brickwork above. Its purpose is to spread the direct weight load of the wall above to prevent it sinking into the earth or falling off vertical. You should not dig any further down and, while it is exposed you will need to ensure the soil next to the lower faces is not eroded by heavy rainfall. Frankly its often best to leave the footing covered to avoid this possibility. The original blackjack coating will have been installed to prevent moisture absorption into the the brickwork from the soils lying against it. This would have been pointless to some extent as any moisture absorbed by the footing brickwork would inevitably rise through the brickwork behind it. Consequently its only real benefit to the property would have been to prevent water splashed from the driveway hitting and resting on the upper wall.

In my view the question becomes what do you plan to the do about the driveway? If you intend to maintain it at this new depth the blackjack coating becomes almost superfluous and some might suggest it should be removed as it may be trapping water in the brickwork that might otherwise evaporate off if the bricks surfaces were exposed. With this in mind I would see no advantage arising from extending the blackjack to cover the bricks of the footings.

 

[Cubist]

Just an afterthought.... damn, I'm getting far too many of those these days - don't be too quick to remove the old blackjack if you've a mind to. If it's thick enough it may be insulating the brick faces from the freeze thaw cycle that may induce spalling. Leave it until the summer if at all possible.

 

[laudan]

Great, thanks for your response Cubist. We'll leave the existing Black jack in place until the summer.