Hello dear building forum community,
My wife and I own an end townhouse, and we would like to build a wooden deck on the garden side. We have a side exit there, so it seems like a perfect spot.
However, we have a major issue: underneath the planned deck area, there are utility lines (electricity and water) located about 80 cm (31.5 inches) deep. Our soil is former farmland, a compacted mix of clay and loam with a high content of stones, ranging from pebbles to sizable blocks.
What type of foundation should we plan for this? We have read a lot already—everything from placing the deck directly on the ground, using driven ground screws, a gravel foundation of only 40 cm (16 inches), up to a full 80 cm (31.5 inches) deep pier or strip foundation, which is said to be frost-resistant. But the utility lines might be in the way of deeper foundations!
My latest idea was a 40 cm to 60 cm (16 to 24 inches) foundation on adjustable screw supports, which could allow me to easily correct any unevenness caused by frost movement.
But what would be the most sensible and safest solution in our situation? Are there any experiences or recommendations regarding this?
I am quite uncertain because once it’s done, there is no going back without additional expenses!
What can I do and what should I do?
My wife and I own an end townhouse, and we would like to build a wooden deck on the garden side. We have a side exit there, so it seems like a perfect spot.
However, we have a major issue: underneath the planned deck area, there are utility lines (electricity and water) located about 80 cm (31.5 inches) deep. Our soil is former farmland, a compacted mix of clay and loam with a high content of stones, ranging from pebbles to sizable blocks.
What type of foundation should we plan for this? We have read a lot already—everything from placing the deck directly on the ground, using driven ground screws, a gravel foundation of only 40 cm (16 inches), up to a full 80 cm (31.5 inches) deep pier or strip foundation, which is said to be frost-resistant. But the utility lines might be in the way of deeper foundations!
My latest idea was a 40 cm to 60 cm (16 to 24 inches) foundation on adjustable screw supports, which could allow me to easily correct any unevenness caused by frost movement.
But what would be the most sensible and safest solution in our situation? Are there any experiences or recommendations regarding this?
I am quite uncertain because once it’s done, there is no going back without additional expenses!
What can I do and what should I do?
T
toxicmolotof4 May 2015 07:48Food for thought: Do you really think that once the terrace is decked, you would completely remove it after frost damage just to re-level it? I don’t think so.
If you want it done properly, you can’t avoid a frost-proof foundation.
If you want it done properly, you can’t avoid a frost-proof foundation.
I would like to do that, but the utility lines are located at the frost protection depth. How high would the risk of frost damage be if we place thick lawn edging stones or something similar around the foundation? Would that reduce the risk?
So far, we have dug about 40cm (16 inches), and the result is in front of me now, and I’m wondering what the best next step is. I haven’t really found helpful information online yet. Of course, the neighboring properties in the development project, who also chose a wooden deck, were able to go down to 80cm (31.5 inches), but they don’t have those troublesome utility lines.
Would, for example, 60cm (24 inches) of compacted fine gravel with lawn edging stones around it be sufficient?
An additional question: The soil is heavily compacted—should it be loosened up or kept compacted?
So far, we have dug about 40cm (16 inches), and the result is in front of me now, and I’m wondering what the best next step is. I haven’t really found helpful information online yet. Of course, the neighboring properties in the development project, who also chose a wooden deck, were able to go down to 80cm (31.5 inches), but they don’t have those troublesome utility lines.
Would, for example, 60cm (24 inches) of compacted fine gravel with lawn edging stones around it be sufficient?
An additional question: The soil is heavily compacted—should it be loosened up or kept compacted?
B
Bauexperte4 May 2015 14:20Papilaus schrieb:
My wife and I have a townhouse end unit, and we want to build a wooden deck on the side facing the garden. We have a side exit there, so it seems like a perfect spot.If the proposed deck encroaches on the setback area, it is questionable whether you are allowed to build it at all.If it does not, a simple gravel bed is sufficient; no need for point or strip footings.
Best regards, Bauexperte
N
nordanney5 May 2015 10:53This is how we built our terrace. About 30-40 cm (12-16 inches) of compacted gravel, then placed on mortar bags or stones. This is already the second terrace we've built in the last 10 years. No pier, strip, or any other type of foundation.
The finished result looks like this:
D
Doc.Schnaggls5 May 2015 15:25Is it a good idea to build over the utility lines, regardless of the type of foundation and terrace?
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