Conservatory base on sloping garden - advice please :)

Jo_anne_2

Hi,

We have had four quotes from local companies for a 3.8m by 4m conservatory. One firm has made a big issue of the fact our garden slopes away from the house and say it will need significant extra work (and money) to make a firm base. There is about 600mm drop from the patio level, to where the conservatory will end. I appreciate this is a significant drop but how much of a problem is this in reality - is it possible they are exaggerating? Advice would be very welcome!

iamcornholio

The foundations need to go to a depth about 450mm lower than the lowest ground level, so it seems that there will be a fair amount of digging and foundation work

tony6403

Each site is different and there is no standard measurement. The footings need to go down to firm ground. I did one where 1200mm had to be removed from the existing levels.

Jo_anne_2

Thanks for your replies. I have summarised below what I think is the base and foundations specifications for our top 2 quotes.

Quote A. Concrete foundations excavated to a min. depth of 600mm for dwarf walls. Compacted hardcore to a min. depth of 100mm then blinded with building sand to eliminate any sharp edges... it then goes on to describe the DPC, etc

Quote B. New concrete base 125mm thick, with mass fill concrete foundation up to 600mm deep. Additional height on base to front and part side elevation to include internal concrete block retaining skin with mass fill MOT stone vibration compacted.


Quote B has an added £1500 for the extra basework. We asked the builder from company A to come and take a look at the site - his opinion was that a stepped foundation would do the job. Company A is certain we need the extra basework to stop the conservatory sliding down the garden. I would be interested to hear what people's views are. :think:

iamcornholio

Stepped foundations may work, or they may be unsuitable. It all depends on the local ground conditions.

Trying to fit a 600mm difference in levels in the relatively short distance of about 4m is a bit of a challenge. One step will be too much, two may be too close together. It may be possible to step the foundations but incorporate some reinforcement into the brickwork to control any potential differential movement/cracking

Jo_anne_2

Thanks for your reply I think if the only difference in price between the two quotes was the extra £1500 cost of the basework, then it would be an easy decision to make!

But Quote A would be around £12k and Quote B around £17k in total. The other quotes we had were around the £12k mark. My instinct is to go for Quote A but am still a bit worried about the conservatory sliding off down the garden! :rotfl: