Swedish cottage extension

[Paul l]

Hi all. New member here..

im extending my wood frame cottage in Sweden   

After removing the topsoil in the footprint of the extension we have found granite bedrock, the highest point of which is just manageable for the required floor height. 

However... there is a depression in the granite that appears to hold water and will only very slowly drain away through cracks in the bedrock. 

We plan to build over the top of this area. Other than blasting a trench, any ideas for the management of this problem? Being Sweden, this will freeze solid in the winter. 

Possible remedies....?

backfill with concrete/substrate?

build on higher footings and ignore?

Photo shows the direction of the fall of the plot, high ground behind me with bedrock only just below the surface making an uperside drain or barrier another problem....

thanks in advance for any ideas...!

[Paul l]

A view of the area dug-out and covered with a weed stopper. 

[Ferdinand]

Welcome to the forum, Paul.

 

Hmmm.

 

Interesting. I'll be as interested as you to see an anwser.

 

The thing that springs to mind is put it on small stilts or some sort of light footprint foundation (you know - eggcrates with gravel type things) in holes you make Or piles. Do you have neighbours? What did they do?

 

What is the rest - can you bridge it in some form from the edge?

 

Ferdinand

(Apporve of people who use tags!)

Edited August 22, 2019 by Ferdinand

[Tennentslager]

Cut a channel with an angle grinder so it drains away?

cut several parallel groves a few mm apart and get busy with a mash hammer and a cold chisel to make the channel 

[Paul l]

1 hour ago, Ferdinand said:

Welcome to the forum, Paul.

 

Hmmm.

 

Interesting. I'll be as interested as you to see an anwser.

 

The thing that springs to mind is put it on small stilts or some sort of light footprint foundation (you know - eggcrates with gravel type things) in holes you make Or piles. Do you have neighbours? What did they do?

 

What is the rest - can you bridge it in some form from the edge?

 

Ferdinand

(Apporve of people who use tags!)

Hi. Thanks!

i have my builder taking a look this afternoon with his foundations guy so appreciate the replies...

yes concrete stilts was an option I was thinking about, and just let the water do what it wants. I guess so long as I can reduce the volume by filling the hole with concrete and/or fine gravel the water will flow under and away quicker...

that leaves the question of insulation in way of the floor structure, proposed as untreated 170x50 pine beams.... standard over here. I could raise the floor on that section to allow more distance from any standing water and damp?

....no neighbors. 

So long as everything can breath there shouldn’t be any damp problems?

[Paul l]

56 minutes ago, Tennentslager said:

Cut a channel with an angle grinder so it drains away?

cut several parallel groves a few mm apart and get busy with a mash hammer and a cold chisel to make the channel 

Hi!

its about 400 mm to the lowest drain height....meaning a 10’ channel

[Carrerahill]

I hope this results in a project post with lots of photos and progress updates! 

[Paul l]

I ran the idea of installing a sump pump under the kitchen floor with an access hatch. The builder agrees that is probably the best option. 

So on Monday we’ll pour some concrete to create a low point exactly where we want it, install the pump/tube casing and fill around with gravel

ok?