The base is the least glamorous part of a conservatory, but it is the part that decides whether the whole structure stays level, dry and warm for the next thirty years. Prices vary more than most homeowners expect, so it pays to understand what you are actually buying before comparing quotes.
For a standard 3m x 3m conservatory, most homeowners in the Bristol area pay somewhere between £1,500 and £3,500 for a traditional dug concrete base with dwarf walls. A larger 4m x 4m base typically runs from £2,500 to £5,000. Priced per square metre, expect roughly £150 to £300 depending on ground conditions and access.
Prefabricated steel base systems are the main alternative. These usually cost £2,000 to £4,000 supplied and fitted for a typical conservatory, and they can be quicker to install with far less mess. They suit sloping gardens well, though not every installer offers them and some homeowners still prefer the solidity of concrete.
A proper conservatory base is more than a slab of concrete. The work usually involves excavating to a suitable depth, laying and compacting hardcore, installing a damp proof membrane and insulation, pouring the concrete slab, then building dwarf walls up to the level the frames will sit on. Footings need to reach stable ground, which around Bristol often means digging deeper where there is clay soil that shifts with the seasons.
When you compare quotes, check whether each one covers soil removal, dwarf walls, damp proofing and insulation. A cheap quote that excludes muck away or leaves the dwarf walls as an extra can end up dearer than an honest all-in price. Ask for the specification in writing so you are comparing like with like.
Access is the biggest single factor. If a digger can reach your back garden, excavation is quick. If everything has to be barrowed through the house or down a narrow side passage, labour time climbs sharply and so does the cost of getting spoil out. Terraced houses in areas like Bedminster or Easton often face exactly this issue.
Ground conditions matter too. Sloping plots need extra excavation or a stepped base, old drains or tree roots can mean rerouting or deeper footings, and poor soil sometimes calls for a reinforced slab. Removing an existing patio, old base or outbuilding adds to the bill as well. None of this is guesswork once someone has actually looked at the site, which is why a firm price should always follow a proper survey rather than a photo.
Most conservatory problems we are asked to look at trace back to the base rather than the frames or glazing. A base that was dug too shallow or poorly compacted will settle, and once it does, doors stick, frames twist and sealed units crack. Fixing a failed base under a finished conservatory costs many times what a proper one would have done in the first place.
A well built base also affects comfort. Insulation under the slab and a correctly positioned damp proof course keep the floor warmer and stop moisture creeping into the dwarf walls, which matters if you want to use the room in a Bristol winter rather than just in July. If a quote seems dramatically cheaper than the others, ask what depth of excavation and what insulation it includes; the answer usually explains the gap.
A confident DIYer can dig and pour a small base, but getting the levels, damp proofing and footing depth right is harder than it looks, and most conservatory installers will only guarantee their structure on a base they have approved. If you do it yourself, agree the exact specification with your installer first.
Most conservatories fall under permitted development, so planning permission is often not needed, and exempt conservatories do not usually need building regulations approval either. The exemption depends on size, separation from the house and heating, so check your specific plans before digging.
A traditional concrete base for an average conservatory usually takes two to five days, plus curing time before the frames go up, ideally around a week. Steel base systems can often be installed in a single day with no curing wait.
Tell us about the job and we will get straight back to you with a free quote. DGL work across Bristol and the surrounding area.
Bristol-based, working across Bristol and the surrounding area.