Repointing brickwork in Oxfordshire and Gloucestershire.
For those requiring a traditional product with uncompromising craftsmanship to match, please call for a full written quotation.
Many red brick buildings were originally constructed using lime mortar and the need to continue this trend is essential to the health of a property as older houses are prone to movement and also need to evaporate water vapour through vapour permeable mortar joints.
If your house is old, say Victorian, it's likely it will have been built from lime mortar and not cement. Therefore, it is essential that you do not use cement in repairs. If it is used then the movement inherent in older properties is likely to result in damage to bricks.
Some builders merchants stock it but you'll have the most success at the The Old House Store in Woodstock
The apex of this North Oxford property had suffered the result of having mortar applied incorrectly. This then weathered badly and needed to be replaced. The photo below shows new NHL 3.5 mortar applied correctly
Here are close-up shots of coarse grain mortar. The large grains of sand provide a rough texture but are absolutely essential for keeping the elements at bay.
Fine aggregates will not stand the test of time. A coarse mix will - fine grains are easily eroded by the weather. Seasonal changes mean thermal movement and the mortar eventually cracks and falls out. In addition to this, mortar made with fine sand does not perform as well where moisture evaporation is concerned as the small grains let less of it pass through the joints.
If you would like to see a video of the project then please click below
Example of recent project before work commenced:
The above photo is a typical example of the type of brickwork repair for which I am often asked to quote. This particular building was originally constructed in 1903 using lime mortar. Nevertheless, over time, weathering had taken its toll to the point where all of the old mortar and many bricks needed replacing.
The photo below shows the depth of raking needed before new mortar can be applied. Shallower depths - although less time consuming to achieve - only result in the mortar cracking and falling out.
The joints are then filled
New creamy natural hydraulic lime now means the brickwork is restored.
There's a tremendous amount of satisfaction to be gained when working outdoors with natural materials
The finished wall below is one which I completed in natural hydraulic lime in North Oxford.
The damaging use of cement
It is always difficult to repair a property where cement mortar has been trowelled over existing lime mortar as the cement mortar is rock hard and can stick to the sides of the bricks making it often impossible to rake out cleanly and without damage.
Using cement strap pointing will also result in the deterioration of bricks as they become the sacrificial element and not the mortar.
When cement mortar is used in the repair process it also waterproofs joints making it difficult for moisture to escape. It then becomes trapped and the result is rising damp and decayed bricks.
One can always tell a good lime mortar finish as - although it may be trowelled in - it will have been brush finished. Without this brushing process there is no calcination. The negation of this process means the joint is not weatherproofed.
Above, this Edwardian house in Poundon had suffered damp therefore the cement mortar was removed and replaced with lime mortar
The traditional and correct practise of brushing is in direct contrast to incorrect trowel finished joints - the consistency of lime mortar simply does not lend itself to this. When lime mortar is correctly brush finished, the aggregates are brought to the surface.
Freezing temperatures or not conducive to brickwork repairs, but neither are baking hot summers. In either case, the newly pointed brickwork needs to be protected with hessian when temperatures are extreme.
Advice: there are still a great many people who are uninformed concerning the correct material for use on old houses. And there are those who will trade on this. Some who lack integrity will pretend they are using lime mortar when in fact they are using white cement. This enables them to complete the work quicker whilst saving money on materials. One must always exercise caution.
There's also the problem of hydrated lime. This is NOT natural hydraulic lime (NHL). Unfortunately it is something which many people - including some tradesmen - confuse with hydraulic lime when the use of lime mortar is specified. All hydrated lime does it to act as a plasticiser which makes cement mortar more workable and therefore easier to apply. Many people believe it makes a mix more porous and flexible in the same way as NHL. It does not. It offers no flexibility or porosity whatsoever and is not strong enought to use as the sole lime based product in a repointing mortar.
The problem with mortar guns
A standard lime mortar mixes uses a lot of sharp sand and this has too many large pieces of aggregate to easily pass through the end of a gun. Therefore soft sand must be used as the grains are much finer. However, the use of this results in cracks because the grains are too small and do not hold together. The only way to stop this is to add cement. Further additions of hydrated lime result in an even more workable mortar. Although NHL is used, the result is not lime mortar but plasticised cement mortar. To then make it even more workable it needs to have a lot of water added to it. Unfortunately, the upshot of a higher moisture content means decreased strength as the grains are held apart thus giving rise to open structures when dry.
Lime putty non-hydraulic lime.
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