Hello all,

I've got a couple of DIY issues I'd like to tackle.

Firstly, I have a concrete block-built garden shed which is letting in water. Seems to be coming in through the bottom course of blocks which is above the damp course. 6 months ago I built a new decking and screwed a length of 4x2 to the outside of the shed as a support, and the trouble seems to have started about then. Every time it rains I'm now having to sweep out 2-3 mm of water. The screws holding the 4x2 to the shed have not penetrated through to the interior.

I am wondering if the solution is to apply some kind of mega-sealant to the inside of the blocks? I really have no idea how to proceed with this problem. Looking for advice. The roof is watertight, and the interior walls feel dry, apart from the bottom half of the bottom course of blocks in the back right hand corner. I do not have any air-bricks or other form of ventilation. I cannot move the decking as it is now cemented into place.

Pictures he
1. Exterior of shed showing position of decking.
http://i760.photobucket.com/albums/x...9-DSC_0053.jpg

2. Close-up of inside showing interior surface of blocks which are wet, and the position of the damp course.
http://i760.photobucket.com/albums/x...9-DSC_0052.jpg

3. Picture of water pooled in the shed, and the bottom course of blocks appear discoloured compared to the rest.
http://i760.photobucket.com/albums/x...9-DSC_0051.jpg

I'd appreciate any pointers on how to proceed, products to try etc.

Thanks and regards.
Jon

On Thu, 09 Apr 2015 03:09:14 -0700, Jon Parker wrote:

Hello all,

I've got a couple of DIY issues I'd like to tackle.

Firstly, I have a concrete block-built garden shed which is letting in
water. Seems to be coming in through the bottom course of blocks which
is above the damp course. 6 months ago I built a new decking and screwed
a length of 4x2 to the outside of the shed as a support, and the trouble
seems to have started about then. Every time it rains I'm now having to
sweep out 2-3 mm of water. The screws holding the 4x2 to the shed have
not penetrated through to the interior.

I am wondering if the solution is to apply some kind of mega-sealant to
the inside of the blocks? I really have no idea how to proceed with this
problem. Looking for advice. The roof is watertight, and the interior
walls feel dry, apart from the bottom half of the bottom course of
blocks in the back right hand corner. I do not have any air-bricks or
other form of ventilation. I cannot move the decking as it is now
cemented into place.

Pictures he
1. Exterior of shed showing position of decking.
http://i760.photobucket.com/albums/x...6/Shed/150409-
DSC_0053.jpg

2. Close-up of inside showing interior surface of blocks which are wet,
and the position of the damp course.
http://i760.photobucket.com/albums/x...6/Shed/150409-
DSC_0052.jpg

3. Picture of water pooled in the shed, and the bottom course of blocks
appear discoloured compared to the rest.
http://i760.photobucket.com/albums/x...6/Shed/150409-
DSC_0051.jpg

I'd appreciate any pointers on how to proceed, products to try etc.

Thanks and regards.
Jon

Block walls (as I know to my cost) are not resistant to standing water -
they are permeable and previous questions on this NG indicate that there
is no simple water proofing product (paint, solution) which can prevent
this kind of penetration. The damp course just stops moisture rising. It
does nothing about water moving sideways.

You need to check the decking to make sure water is not running down it to
the shed, and also check the 4 * 2 to make sure that it is not holding the
water against the wall instead of letting it run off. Finally check that
you haven't left something under the decking against the shed wall which
is stopping water draining away.


This does look very much like the problem that I had.
From the pictures it looks as though your shed is built directly onto a
concrete slab and the DPC is below the bottom course of blocks.
I can also see that the concrete slab has an external lip which is wet.

I would guess that the decking is chucking water against the wall, it is
running down the wall then sitting on the concrete slab and running
sideways under the wall.

I cured my problem (more or less) by pointing the base of the wall with a
load of mortar to provide a "flaunching" like you would find around a
chimney pot.

This throws the water off the edge of the slab so it can't stand and then
run under.

I also went round to improve the drainage as I found that parts of the
surrounding material were "wicking" water up the side of the base and onto
the slab.

I would also consider taking steps to prevent water running off the
decking onto the wall and slab base.

This could be as simple as removing the last bit of decking so that the
run off doesn't reach the wall, or perhaps putting a wooden barrier across
the top of the decking and drilling drain holes along the deck side to
allow proper drainage away from the wall and slab.

Before you added the decking the guttering would have kept most of the
water off the wall.

Cheers


Dave R

--
Windows 8.1 on PCSpecialist box

On Thu, 9 Apr 2015 03:09:14 -0700 (PDT), Jon Parker
wrote:

Firstly, I have a concrete block-built garden shed which is letting in water. Seems to be coming in through the bottom course of blocks
which is above the damp course. 6 months ago I built a new decking and screwed a length of 4x2 to the outside of the shed as a support,

By doing this you created a dam for water coming off the decking
and/or down the wall. It will penetrate the block, which is porous,
and get inside.

and the trouble seems to have started about then. Every time it rains I'm now having to sweep out 2-3 mm of water.
The screws holding the 4x2 to the shed have not penetrated through to the interior.

They only need to penetrate the paint.

I am wondering if the solution is to apply some kind of mega-sealant to the inside of the blocks?

If you do that the blocks will retain a lot of water and in low
temperatures the entrained water will freeze and break up the block.

I really have no idea how to proceed with this problem. Looking for advice.

You need to prevent water getting onto your support. Ideally remove
the decking and rebuild it with a gap between it and the shed and
support on the ground - not the shed wall.

You might get away with using a sealant on the join between the
decking and wall but everything must be very dry before doing this.
The sealant should be formed to create a lip so water running down the
wall will go onto the decking. You might also need to cut a groove in
the decking near the wall across the existing groves to allow water on
the decking to drain away.

On Thu, 9 Apr 2015 03:09:14 -0700 (PDT), Jon Parker wrote:

6 months ago I built a new decking and screwed a length of 4x2 to the
outside of the shed as a support, and the trouble seems to have started about then. Every time it rains I'm now having to sweep out 2-3 mm of
water.

Looks like the water is either coming through the blocks from where
it gets stopped by the 4x2 against the wall or undeneath between the
wall and slab.

Block sealants aren't a proper solution. Think I'd lift the decking,
remove the 4x2 and pack it away from the wall on 1/2" or 3/4 thick
4x4 treated timber packing pieces at each fixing point. Trim the
decking boards 1/4" short of the back edge of the 4x2 and refit.

Is the bottom edge of the 4x2 resting on the slab? If so that's not
good, either lift it 1/2 to 3/4" or trim the bottom edge by that
amount. Combined with the packing pieces the 4x2 is now in air and
not touching the wall/slab. You could pack up the 4x2 for load
bearing, but put DPM between the top of the packing and the 4x2 and
stagger them with the wall fixing packers.

The idea of the above is to not drain or trap water against the
wall/slab and to give ventilation so any water that does get there
can dry quickly.

Another possiblity is to lift the decking and fit some suitably wide
DPM partly up the wall (trim later to top of decking boards?) over
the top of the 4x2 and down to the ground. Not so good for the life
of the 4x2 as it can't really dry out well and if the water is coming
through the wall might not cure the problem as without cutting a slot
in the wall to take the DPM and mortoring in place like flashing
water will get behind it.

--
Cheers
Dave.

On 09/04/2015 11:09, Jon Parker wrote:
Hello all,

I've got a couple of DIY issues I'd like to tackle.

Firstly, I have a concrete block-built garden shed which is letting in water. Seems to be coming in through the bottom course of blocks which is above the damp course. 6 months ago I built a new decking and screwed a length of 4x2 to the outside of the shed as a support, and the trouble seems to have started about then. Every time it rains I'm now having to sweep out 2-3 mm of water. The screws holding the 4x2 to the shed have not penetrated through to the interior.

I am wondering if the solution is to apply some kind of mega-sealant to the inside of the blocks? I really have no idea how to proceed with this problem. Looking for advice. The roof is watertight, and the interior walls feel dry, apart from the bottom half of the bottom course of blocks in the back right hand corner. I do not have any air-bricks or other form of ventilation. I cannot move the decking as it is now cemented into place.

Pictures he
1. Exterior of shed showing position of decking.
http://i760.photobucket.com/albums/x...9-DSC_0053.jpg

2. Close-up of inside showing interior surface of blocks which are wet, and the position of the damp course.
http://i760.photobucket.com/albums/x...9-DSC_0052.jpg

3. Picture of water pooled in the shed, and the bottom course of blocks appear discoloured compared to the rest.
http://i760.photobucket.com/albums/x...9-DSC_0051.jpg

I'd appreciate any pointers on how to proceed, products to try etc.

Thanks and regards.
Jon


Two possibles, or a combination of both;

The 4 x 2 should have been spaced 100 from the wall, so could be
trapping water.

Or

Rain water is bouncing off the hard deck surface onto the wall.




--
Dave - The Medway Handyman www.medwayhandyman.co.uk

Jon Parker wrote:

I am wondering if the solution is to apply some kind of mega-sealant to the inside of the blocks?

You could try Wickes liquid damp proof course, it's a rubbery/bitumen I
put some under a deep layer of floor levelling and around the bottom
course of bricks on a porch which had a pretty ropey DPC (if any) where
damp and weeds and ants found their way in ... been OK for about a year.

Thanks, that's given me some ideas :-)

Jon

On Thursday, April 9, 2015 at 11:57:34 AM UTC+1, Peter Parry wrote:
You need to prevent water getting onto your support. Ideally remove
the decking and rebuild it with a gap between it and the shed and
support on the ground - not the shed wall.

Thanks, that's given me some ideas :-)

Jon

On Thursday, April 9, 2015 at 2:28:06 PM UTC+1, Dave Liquorice wrote:
Looks like the water is either coming through the blocks from where
it gets stopped by the 4x2 against the wall or undeneath between the
wall and slab.

Agreed.

Is the bottom edge of the 4x2 resting on the slab? If so that's not
good.

No, it's about 2-3 inches above the concrete base.

Thanks, that's given me some ideas :-)

Jon

On Thursday, April 9, 2015 at 6:28:57 PM UTC+1, The Medway Handyman wrote:
The 4 x 2 should have been spaced 100 from the wall, so could be
trapping water.

This sounds like the culprit!

Jon

On Thursday, 9 April 2015 18:28:57 UTC+1, The Medway Handyman wrote:

The 4 x 2 should have been spaced 100 from the wall, so could be
trapping water.

100 what? Inches (analogous to the 4 x 2)? Cubits?

On 10/04/2015 08:38, wrote:
On Thursday, 9 April 2015 18:28:57 UTC+1, The Medway Handyman wrote:

The 4 x 2 should have been spaced 100 from the wall, so could be
trapping water.

100 what? Inches (analogous to the 4 x 2)? Cubits?


Well WE know what he means! Pronounced fourbetoo down 'ere. Metric
hasn't reached chippies yet