Sealing bricks on an old property

[18yearstooold]

My gable end needs repointing

It's 1880s construction

I've had 2 quotes

One will use lime mortar and has said not to seal the bricks as it will potentially cause internal damp -he has included replacing 6 bricks that are damaged

The other has said he will use cement mortar and to seal the bricks to protect them and the bricks don't need replacing if they are sealed

How do I know which one to trust?

My property is of similar vintage and my fairly extensive research indicates that lime mortar should be used for such buildings if lime mortar was used originally which is very likely to be the case.

Victorian houses are not designed to keep out water like modern houses. What they do is have mechanisms for water absorbed during wet weather to be released. This is where lime mortar comes in. Water will move back into the atmosphere through whichever is the weakest, the mortar or the brick. Victorian bricks are soft compared to modern bricks so need a soft (lime) mortar. If you use a cement mortar in a Victorian property, water will move through the bricks instead of the mortar, eventually over time causing deterioration of the brick surface. This is called spalling. What you want is for the mortar to deteriorate and then in a hundred years or so, the brickwork gets repointed.

I'd say the first guy knows what he is talking about. I don't know how effective sealing brickwork is, but if it is really effective, then you will be blocking moisture from within the house (bathing, cooking, breathing) from escaping. Sure opening windows and extractor fans will help, but so will the in-built mechanisms of the victorian house. Also, what if you have a penetrating damp problem like a blocked downpipe. The damp will only be able to be released into the interior of the house.

I would just be careful about exactly what is meant when people say lime mortar. I know a 6:1:1 mix (6 parts sand to 1 part lime and 1 part cement) used to be know as the mix to be used in conservation cases. The small amount of cement is thought to protect against excessive weathering. However nowadays many are not using any cement at all. I mean if the building has survived for over a hundred years without cement, why start using it now?

What chaplin said. The first builder knows what they're doing. The second doesn't.

my dh deals in conservation don't seal bricks for reasons above, lime mortar like original unless you want to solve 1 problem and cause 2 bigger and more expensive problems