Specialist repair services for masonry, sealant and building envelope failures
Northern Seal & Joint carries out a specific set of repair and treatment services - all focused on the building envelope. We do not carry out general building work. Every service listed below addresses a specific type of failure: failed mortar, open joints, perished seals, deteriorating masonry, or unprotected surfaces. If your problem falls within our scope, we will fix it correctly and permanently. If it doesn't, we will tell you so.
Our approach
Every repair follows the same sequence regardless of scale:
Diagnose first. We identify the root cause - not just the visible symptom. A damp patch is an outcome; the open mortar joint or failed sealant bead causing it is the problem we fix.
Remove completely. Failed materials are removed in full before anything new is applied. Applying new sealant over old, or pointing over soft mortar, produces a repair that will fail again.
Specify correctly. The right product for a joint depends on substrate type, movement characteristics, exposure level and - on older buildings - the materials the structure was designed to work with. Lime on pre-1920s stone. Correct-grade NHL for the exposure zone. Flexible sealant in moving joints; rigid mortar only where there is no movement.
Finish properly. Clean, neat, durable. We leave the site as we found it.
Find the problem you’re dealing with
Cement mortar repointing
For brick and stone buildings where mortar joints have cracked, eroded or failed. We rake joints to sound material, specify the correct mix for the substrate and exposure, and repoint to match the original joint profile - flush, weatherstruck, bucket-handle or recessed. Admixtures including SBR, plasticiser and frostproofer are used where conditions require it.
Internal sealant replacement
For failed sanitary sealant in bathrooms, kitchens, wet rooms and around internal wet-area joints. Full removal of the existing bead - including mould treatment - and replacement with correctly specified sanitary-grade material. We do not apply new sealant over old.
Patio pointing and repair
For failed jointing between paving slabs - sand-cement or resin-based depending on the slab type, the degree of movement, and the client's requirements. Old joint material is fully removed before new jointing is applied. Resin products offer longer life and better weed resistance in exposed Yorkshire conditions.
Lime mortar repointing
For pre-1920s stone and brick buildings that were built with lime mortar and should never have had cement applied to them. We work with NHL 2, NHL 3.5 and NHL 5 depending on the stone type and exposure, as well as lime putty and hot mixed lime for conservation and heritage projects. All lime work follows BS 7913:2013. We carry out listed building and conservation area work as standard.
Window and door gasket replacement
For compression gasket failure on UPVC, timber, aluminium and steel window and door frames. We source the correct replacement profile for the specific frame system and carry out a full perimeter replacement. Heritage steel frame windows - Crittall and equivalents - are a specialism within this service.
Breathable water repellent treatment
For brick and stone walls that are absorbing excessive water. Silane/siloxane penetrating treatments line the pores of the masonry without sealing the surface, so water beads off while vapour can still escape. Invisible when dry. Suitable for older solid-wall buildings where breathability must be preserved. Applied after repointing is complete and cured.
External sealant replacement
For failed perimeter joints around windows, doors and material interfaces on external elevations. Old sealant is fully removed, substrate prepared, backing rod installed, and the correct external-grade sealant applied for the joint type and movement. We use professional-supply polyurethane and hybrid products - not retail silicone.
Masonry repair
For cracked, spalled or loose brick and stonework. We assess whether the damaged unit requires repair in place (using compatible repair mortars) or full replacement, source matching materials, and carry out the repair to blend with the surrounding masonry. All work on listed buildings is carried out to conservation requirements.
Not sure which repair is needed?
Sometimes the correct repair route isn't obvious from the outside - particularly on older solid-wall buildings with complex moisture histories. Our Building Leak and Damp Inspection service diagnoses the cause before any repair cost is committed. We identify what is failing, where, and why - then recommend the correct repair route.