Ask Your Question

Angie's List Answers is the trusted spot to ask home improvement and health questions and get answers from service companies, health providers and consumers. For ratings and reviews on companies in your area, search Angie's List.

 
 
or
Submit
Top 30 Days Experts
Rank Leader Points*
1 kstreett 240
2 Guest_9020487 110
3 Guest_9190926 105
4 GoldenKid 100
5 ahowell 95
6 KnowledgeBase 95
7 skbloom 80
8 Guest_98024861 70
9 Guest_9311297 70
10 Guest_9400529 70

*Updates every 4 hours

Browse Projects By Category

Question DetailsAsked on 4/12/2016

Should sand be applied prior to a Vapor barrier?

Do you have the same question? Follow this Question


1 Answer

0
Votes

Assuming you mean under a basement slab or crawlspace vapor barrier - then yes if your soil or base has any sharp stones or coarse sand in it. On pure clay or sandy/silty soil without material that could penetrate the vapor barrior a sand overlay is not necessary, though my practice is to grade the soil to drain to a point where it can easily be recovered - a corner sump or existing sump pump pit, so you don't get stagnant water smell. On impervious silty/clayey soil a sand layer over the top can promote that drainage.


Rake the soil to remove larger material and sharp stones, put down 1/4-1/2" mason's sand (NOT beach sand or coarse crushed traction sand - organic odor risk / sharpness issues respectively), and if going under concrete slab compact with plate compactor before putting down vapor barrier and slab. If open crawlspace, especially if route for access to HVAC/plumbing, I leave 6-12" extra vapor barrier each way so it is not pulled tight - makes it less likely to tear when crawled on.


And remember vapor barrier has to be fastened to the foundation wall to be effective - can use caulk at wall, VB, then overlying wood firring strip to hold the VB to the wall. There are also polyurethane sealants designed to seal VB to concrete/block, though I would not count on that alone - I use 2x2 cedar strips to hold it to the wall.


If a crawlspace VB and you have buried lines that might have to be dug up in the future under there, use wall anchors like screws into drywall anchor inserts that can be removed so the VB can be pulled back if needed in the future. If that possibility, fasten the VB with the caulked line under the top edge of the wood strip, so when it is removed the VB can be cut at the bottom of the caulked edge to loosen it up, then when work is done VB can be reapplied to the cut line with a new caulk line and firring strip can go same place a second or even third time if needed, without drilling new holes in the foundation for the screws. Another reason for the slack in the VB also.


If crawlspace/concrete slab underdrainage might run through the sand, be sure to put a permanant (not garden type) filter fabric and fine gravel drain at the downflow end BEFORE it gets to the sump pump sump, so the sump pump is not pumping sand.

Answered 2 years ago by LCD




Related Questions


Terms Of Use
|
Privacy Policy