Conservatory movement
Cracks around a conservatory base
Send details of the cracks you have noticed around your conservatory. A specialist firm can review them and advise whether the movement matters, with no cost or obligation to you.
Why conservatories move more than the main house
A conservatory is much lighter than the brick walls it leans against. Builders usually pour shallow strip footings for it because the structure does not need the deep foundations that support two storeys of masonry and roof tiles. That difference in depth means the two parts of the building respond differently to the ground beneath them.
When the soil dries out in summer, clay shrinks. The shallow footings under the conservatory drop first because they sit closer to the surface where moisture changes are sharpest. The main house, resting on deeper foundations, barely moves. So a gap opens at the joint where the lighter structure meets the heavier one.
This separation is common across Kent, particularly where homes stand on Weald Clay or Gault Clay. It does not automatically mean the main house is failing. The conservatory is simply reacting to conditions its shallow footings were never designed to resist. Understanding that distinction stops a lot of unnecessary worry.
Reading the cracks at the junction
The place to look first is the vertical joint where the conservatory frame or dwarf wall meets the house. A straight crack running from floor to eaves suggests the lighter structure is dropping away. If the crack tapers, wider at the top and tight at the bottom, the conservatory is tilting outward. Both patterns point to footing movement rather than a problem with the house itself.
Check the inside too. Doors between the rooms may start to catch on the carpet or fail to latch because the frame has twisted slightly. Skirting boards might separate from the floor along the shared wall. These signs confirm that the movement is localised to the addition.
If cracks appear in the main house walls well away from the conservatory, the picture changes. That spread suggests something affecting the deeper foundations, like a leaking drain or tree roots drawing moisture from under the whole footprint. At that point the conservatory is a symptom rather than the cause.
What the ground underneath is doing
Late July is when clay soils in Kent reach their driest state. Months without heavy rain leave the ground contracted, and shallow footings settle into the gaps. A conservatory built on clay will show its widest cracks around now. They often close again once autumn rain returns and the soil swells.
But clay shrinkage is only one possibility. A broken drain running under the slab can wash fine particles away, leaving a void. Water pooling against the base after storms softens the bearing capacity of the soil. Tree roots from a nearby boundary hedge may be extracting moisture unevenly from one side of the footing.
Each cause requires different evidence. A drainage survey uses a camera to check for leaks under the slab. Boreholes reveal what the soil is made of and how dry it has become. Without that information, guessing at the reason risks paying for work that addresses nothing.
Monitoring before any repair starts
Rushing to fill the cracks with mortar hides the evidence a specialist needs. Before anyone proposes a fix, they will want to know whether the movement is still happening or settled long ago. Crack monitoring involves fixing small gauges across the opening and taking readings over several months.
Those readings show the direction and speed of movement. A gauge that records steady widening through summer and partial closing in winter confirms seasonal clay behaviour. One that keeps opening regardless of rainfall points to a continuing trigger like a leak or root growth.
Only after that pattern is clear can a specialist firm decide what to do. The answer might be as simple as redirecting a downpipe. Or it might involve resin injection to stiffen the ground beneath the slab, or screw piling to transfer the load past the weak layer to firmer strata below. Monitoring prevents expensive guesswork.
When underpinning becomes necessary
Underpinning a conservatory is a smaller job than underpinning a house, but the principle is the same. A specialist firm excavates sections of the existing footing and pours concrete below them to reach stable ground. Because the structure is light, access is usually straightforward and disruption stays outside.
Resin injection offers an alternative where digging is impractical. A specialist pumps expanding resin beneath the slab to fill voids and compact loose soil. Screw piling drives steel shafts through the weak layer until they grip something solid, then brackets transfer the weight of the base onto them.
None of these methods suit every situation. The choice depends on what the monitoring showed, what the soil investigation found, and how much load the new support needs to carry. A structural movement survey pulls those threads together so the right repair happens once.
Ask about cracks around your conservatory
Describe what you have seen and where the conservatory sits on your home. A specialist firm will read the details and advise whether a site visit makes sense, without committing you to any work.
- No fee to enquire
- No obligation to proceed
- Specialist advice